Standard version 5.0 April 2024

The NSCS has the same scope as BS EN 13670 for Building Structures. It provides a framework for providing additional information on lightweight concrete, use of fibres, special designs, the integration of concrete products into a design and defining responsibilities between the parties. It is intended to be used with the ICE Specification for Piling and embedded Retaining Walls for foundation structures – SPERW.

The NSCS is laid out in terms of processes, and it uses the same sequence as BS EN 13670. European and British Standards are referenced rather than reproduced within the document.

The NSCS covers requirements for the construction of concrete building structures of in-situ concrete, precast concrete, and hybrid concrete systems. It is intended for use with structures designed to BS EN 1992, although it can be used when other design standards are used. Where the NSCS is to be used for structures in extreme environments, those produced by specialist construction techniques or those of a specialist design nature, the Project Specification should include the particular requirements where appropriate.

The NSCS is written with safety in mind but does not specify Health and Safety requirements as they are legal regulations that apply to all construction and are inherent within this specification. In the UK designers must comply with the CDM Regulations. This requires designers to assess risks and design them out where possible, to do this they must understand the process required to achieve each aspect of any design – the weight of units to handled, the implications of creating any special finish, etc.

Where the NSCS refers to specifications, standards or regulations this shall be to the latest edition. 

Specific obligations are placed on the Constructor, the Client and the Engineer. In some cases these will be different organisations; sometimes any or all will be represented by the same organisation. However, their responsibilities remain as required under the Contract.

The NSCS Project Clauses are to be read in conjunction with these Standard clauses and outline project information specific to a particular project that is additional to the requirements of Standard Clauses.

The NSCS Project clauses cover the exchange of information necessary between the Client  and Constructor at tender stage and contract stage. Completion of the Project clauses is intended to be as required for the stage for which it is being used, i.e. at time of tender or contract commencement.

The NSCS Project clauses allow the Engineer responsible for the design the freedom to incorporate specific text to vary and add to the Standard clauses at tender. Likewise the Constructor can propose variations when returning the tender. It is emphasised that the Standard clauses have been produced as a non-prescriptive specification to meet the standards required by BS EN 13670 and therefore any amendments through the Project clauses should be as few as possible.

The Standard clauses cannot be altered; they can only be amended by using the Project clause P4.1.1.1.

This allows those receiving the specification, Principal Contractor, Constructor, Concrete Producer, Precast Concrete Manufacturer, Specialist designer etc. to be clear about project changes and requirements.

The pro-forma layout of NSCS Project clauses acts as an aide memoire to the disclosure of relevant information for most types of project.

NSCS Guidance provides background information on the content and explains why certain clauses have been adopted. NSCS Guidance is designed to be ‘dipped into’, and read with the relevant Standard and Project clauses; as a result there is some intentional duplication.

The specification for the structure shall be the National Structural Concrete Specification for Building Construction – NSCS.

The NSCS Project Specification is provided by the Client at tender and identifies the appropriate information specific to the structure which includes the NSCS Standard Clauses. Standard Specification Clauses may be modified by information given in the Project Clauses.

The following definitions, in addition to those given in BS EN 13670, apply for the purpose of this Specification.

When by or of the CA, agreement or acceptance shall have the following limitations.

When given in respect of samples of materials, execution or proposals for methods of construction submitted in accordance with this Specification, shall not be interpreted as denoting any degree of satisfaction with the materials used in, or the execution of the Works.

When given in respect of drawings, documents, or schemes called for by the Specification or proposed by the Constructor, is only for conformity with the design concept and design information given in the Contract Documents or contained in subsequent instructions from the CA.

Acceptance or agreement shall not diminish or relieve the obligations of the Constructor under the Contract.

Plan that explains how the information management aspects of the appointment will be carried out by the Constructor.

Organization or person for which/whom a construction project is carried out.

The specialist concrete firm constructing the works.

The named individual or company, engaged to act for and on behalf of the Client for the purpose of accepting proposals from the Constructor, issuing technical information to the Constructor and monitoring the work of the Constructor.

The calculations produced generally by the Engineer. For some specialist work they may be produced by a specialist designer working for the Constructor.

Plans and sections indicating the layout and dimensions of each floor of the Works. The drawings will be in sufficient detail to allow the formwork to be constructed and will show or reference all inserts or cast­in items and holes. Drawings should indicate the locations of concrete grades and finishes.

Drawings prepared to show the design information required to enable reinforcement detail drawings to be produced.

Detailed and dimensioned general arrangement drawings by Manufacturers or Suppliers for the layout of precast planks, waterbars, membranes, inserts and mould drawings for special precast units including prestressed, etc.

Fully dimensioned drawings, plans and cross-sections of tendons and anchorage layouts indicating tendon profiles at regular intervals along each length, support details, stressing sequences etc.

Stressing end, dead end anchorages, and any ordinary reinforcement sizes and locations required to supplement the post-tensioning design and bursting reinforcement at anchorages to suit anchor type and layout, shall be clearly defined.

Drawings prepared to show the layout of the various types of reinforcement used in the construction of the Works. They shall be prepared in accordance with the requirements of BS EN 1992 and the Standard method of detailing structural concrete – A manual for best practice – IStructE.

Schedules prepared to show the details of each bar to be cast into the concrete. They shall be prepared in accordance with BS 8666.

Drawings, sketches or other information, prepared by the CA, indicating any special requirements or methods, which the Constructor must consider in the preparation of their temporary works in order to erect the Works in a safe manner.

Drawings prepared to show necessary falsework, formwork and propping that are employed to construct the Works in a safe manner.

Drawings prepared to show coordinated builders’ work – holes, cast-in services and fixings, etc.

Drawings to indicate what was built.

The individual or organisation responsible for the overall design of the Structure.

An area of publicly accessible concrete finish from previous projects, including those listed on MPA The Concrete Centre website, or the CONSTRUCT Example panels that demonstrate the project expectations for:

• standard of plain formed finishes
• standard of ordinary formed finishes
• special formed finishes

A bespoke project specific physical trial construction.

A part of the structure built in advance of the area where the finish is required that defines the standard expected for the project.

For pre-cast concrete the individual or organisation that supplies factory produced precast concrete; including elements, products built in accordance with the CA’s supplied design and drawings, and proprietary products designed by them to meet the design brief given by the CA.

Concrete that is subjected to pre-tensioning or post-tensioning.

The organisation supplying concrete for site construction.

National structural concrete specification for building construction – NSCS Standard Clauses and NSCS Project Clauses.

The designated place where the Constructor will construct the Works.

Anyone working for the Constructor or a Manufacturer who completes the detail design of any part of the structure to meet the requirements set out on the GAs and design information drawings.

The named individual, or individuals, employed by the Constructor responsible for coordinating the temporary works for construction of the works.

Structure to be built by the Constructor.

Specialist designer who co-ordinates the detailing for water-resistant concrete in accordance with BS 8102.

Execution shall be in accordance with BS EN 13670 as supplemented by the Project Specification and all statutory requirements.

Where there is a difference between the requirements of BS EN 13670 and the Project Specification, the Project Specification takes precedence.

All materials used in the structure shall comply with the Project Specification and current versions of standards referred to therein. The CA may specify samples for testing and the Constructor shall arrange for such samples to be supplied, identified, stored and tested and the results delivered to the CA in accordance with the relevant standards and the Project Specification requirements.

Allow reasonable access to the site for technical inspection by third parties at all times.

Where water-resisting construction is specified, submit to the CA for agreement: details of the materials used and the execution, which are to be in accordance with BS 8102; and written confirmation from the supplier of the water-resisting materials that they will not be adversely affected by the proposed environment, concrete, curing and release agents, placing methods, joints, finishes, reinforcement and its support details, or loads.

All supervisors and operatives shall have the appropriate knowledge, training and experience for carrying out their tasks on site.

All materials used in the construction for both temporary and permanent works should be responsibly sourced to a sector certification scheme in accordance with BS8902, with appropriate third-party certification against BES6001 whenever this is available; all material should be used sustainably with waste minimised.

Operate an agreed quality management system, which shall be accessible for audit.
The Constructor shall prepare a quality plan for the project; and give this the CA for acceptance at least five working days before the Works start.

Produce the documents as required and provide to the CA at the time stated in clause P4.3.2.1.

When the Project Specification is revised all changes must be clearly identified.

Copies of all documents required for the construction of the structure, including all inspection reports, shall be available for review on site during the contract period.

The Constructor shall ensure that the coordinated information they prepare, as required by the Project Specification Tables P1.2, P4.1.1.1, P4.3.2.1, P4.3.2.2, P8.1, & P9.8 and clauses P2.5, P2.6, P2.7, P4.1.2.2 & P8.2.1.1 is submitted to the CA for agreement in accordance with the Project Specification requirements.

The Constructor shall contribute to the project BIM model exchange, change control and coordination procedure as outlined in the BEP.

Where a project does not use a common data environment as set out in the BEP the Constructor shall maintain a register of all documents they receive and issue, identifying the source of the document, revision symbol and date received or issued by the Constructor.

The dates for issue of documents shall be in accordance with the Project Clause P2.5, agreed with the CA and recorded in the quality plan.

All models and shared data must be in accordance with the project BEP Where information on a model is updated the alteration should be clearly identifiable.

To be in accordance with BS EN ISO 4157. Revisions, with the date made, and status shall be clearly shown. A circle or cloud around drawing revisions should identify the changes made for the latest revision symbol. The changes should be described in notes on the drawing corresponding to the latest revision symbol.

Drawings are to be produced as detailed in the table given in clause P2.5. Where the drawings are to be prepared by a manufacturer of precast concrete products, or a specialist post­ tensioning contractor, the Constructor is to ensure that the drawings are issued to the CA in accordance with the requirements of Project Clause P2.5 and the project BIM execution plan.

The CA and Constructor shall each be responsible for the accuracy of any schedules that they produce.

Where the Constructor is to produce coordinated builders’ work drawings the CA shall provide the required information in accordance with an agreed programme.

The CA’s construction sequence information must be considered in the preparation of the Constructors’ temporary works drawings showing all stability requirements during erection.

Temporary conditions and loading on partially constructed permanent structure must be assessed by the Constructor.

Method statements for erection and dismantling of temporary works including all details of propping/ re-propping and backpropping through the structure are to be prepared by the Constructor and agreed with the CA.

The works are to be built in accordance with Execution Class 2, other than for post-tensioned construction where Class 3 is to be used, unless otherwise specified in clause P4.4.1.1.

Set out the structure to the given setting out information.

In addition to the Constructor’s inspection of the materials and execution in accordance with BS EN 13670 the Constructor is to give reasonable notice, as given in P4.3.2.2, to allow inspection by the CA at the following stages:

• Before each concrete pour.
• Before prestressing work starts.
• Before covering up or backfilling.
• For water-resisting construction to allow inspection jointly with Constructor as Cl. 8.4.2 of this Specification

Obtain the written agreement of the CA to any modifications of this Specification before any work is started.

All materials shall be stored in an agreed manner that prevents damage or degradation and is in accordance with all manufacturers’ requirements.

The CA shall comment on all information supplied within five working days of receipt. Acceptance or agreement by the CA shall have no effect unless given in writing.

Supply electronic copies of all test reports to the CA as soon as they are available.

• Any test or inspection reports that show that any part of the structure does not meet the specified criteria shall be issued to the CA, as soon as they are available.
• Provide proposals for dealing with the non-conformity to the CA within five working days of reporting the issue.
• A course of action shall be agreed within a further five working days. Where the Constructor is responsible for a non-conformity the cost of all additional testing and remedial works shall be at the Constructor’s expense.

Design and construction should be in accordance with the following where applicable:

• BS 5975-1: Temporary works. Management procedures for the control of temporary works – code of practice
• BS 5975-2: Temporary works. Falsework: Design and implementation – code of practice
• Formwork: a guide to good practice: Concrete Society Publication CS030 2012
• Guide to flat slab falsework and formwork: Concrete Society publication on behalf of CONSTRUCT, CS140, Pallet, 2003.
• Formwork striking times – Criteria, prediction and method of assessment: CIRIA Report 136, Harrison, 1995
• BS EN 1990 Eurocode Basis of Structural Design & BS EN 1991 Actions on Structures
• BS EN 12812 Falsework – Performance requirements and general design

Permanent formwork may be used subject to the agreement of the CA.

All formwork and falsework materials should be sustainably sourced with appropriate third-party certification whenever this is available; and shall be used sustainably. Where practicable provide an EPD or equivalent confirmation of the global warming potential of the formwork in kgC02e/kg.

Formwork should be prefabricated where practical and handled with care to maximise reuse and minimise wastage.

Release agents shall be chosen to suit the method of construction, and the finish required. They shall not be adversely affected by the weather.

Concrete shall not be cast directly against existing construction or faces of excavations without prior agreement of the CA. Where structural concrete relies on permanent or temporary support from the ground, ensure that the support is firm enough for concreting operations.

Formwork shall be clear of all debris, water, snow and ice before concrete is placed.

Set out and fix all cast-in items shown or referenced on the drawings. Any clashes between holes, cast in items and reinforcement shall be resolved to the agreement of the CA before any concrete is placed.
Block out items shall be cleared out after concreting.

Through ties may be used to support vertical faces of formwork other than in water-resisting construction or as agreed with the CA.

No ferrous metals shall be left in the concrete cover zone when formwork has been struck.

Any formwork tie holes left exposed to view in the faces of the concrete shall be filled to the agreement of the CA.

Ensure the structure is not subjected to temporary loads during construction that will cause distress, taking account of the maturity of the concrete at the time of loading.

Falsework and formwork shall be struck at a time determined by the Constructor to comply with this Specification.
Formwork shall be removed carefully so as to avoid damage to the concrete surface.

The exact sequence of propping/re-propping and backpropping through the structure, set out in a method statement by the Constructor, shall be agreed with the CA in advance, and should have no damaging effect on the Permanent Works.

Any special requirements for the formwork design, including any use of heated forms or changes in design formwork pressure for concreting in cold weather, shall be agreed with the CA in advance.

Produce drawings showing the lay out of construction joints and agree their location with the CA. Joints are to be positioned so as not to cause the structure any distress.

The pour sizes proposed and justified by calculation by the Constructor, shall be agreed with the CA in advance; if not they shall be as shown below.

Use appropriate method of creating good construction joint surfaces, so scabbling using hand tools should not be required.

Use waterstops in all construction joints and movement joints in accordance with the manufacturer’s written instructions. Obtain the agreement of the CA for the methods to be used to maintain them in their correct locations and prevent damage while concrete is being placed and during or after removal of the formwork. Hydrophilic water stops should be protected from premature swelling under wet conditions.

Submit for agreement with the CA drawings indicating the positions of joints and details of waterstops to be used. Details shall include schedules of all junction pieces, which shall be purpose made, and isometric layouts of waterstops.

Where centre section waterstops are proposed, submit to the CA for agreement the methods to be used to ensure full compaction of the concrete around the waterstop.

Formwork ties used shall be of a type to maintain water resistance of the construction.

Where a method of fixing formwork requires holes through the concrete section, details shall be agreed with the CA.

All stainless steel reinforcement shall conform to BS 6744.

All other reinforcement shall conform to BS 4449, BS 4482 or BS 4483 as appropriate.

All reinforcement shall be cut and bent in accordance with BS 8666.

All reinforcement should be sustainably sourced with appropriate third-party certification whenever this is available; and shall be used sustainably. Provide a site, product and manufacturing route specific EPD conforming to BS EN 15804 or equivalent confirmation of the global warming potential (total covering modules A1, A2 and A3) of the reinforcement in kgC02e/kg.

Unless agreed otherwise by the CA, all reinforcement shall be obtained from firms holding a valid UKAS approved product approval certification for the production and supply of steel reinforcement against the requirements of BS 8666. A supplier Certificate of Approval reference shall be stated on all documentation.

Unless agreed otherwise by the CA, all cutting and bending operations shall be conducted by firms holding valid UKAS approved product approval certification for the processing and supply of steel reinforcement against the requirements of BS 8666. A supplier Certificate of Approval reference shall be stated on all documentation.

Supply, detail and fix all spacers – chairs, blocks, supports and devices of a special nature required to hold the reinforcement in the correct position during concreting. The materials and workmanship shall be in accordance with BS 7973: Spacers and chairs for steel reinforcement and their specification. Ensure that the spacers have the required performance characteristics. The type and layout of the spacers should be agreed with the CA before any work is started.

Proprietary continuity strips can be used subject to agreement by the CA.

Unless otherwise agreed by the CA, the continuity strip manufacturers shall hold:

• a valid CARES Technical Approval scheme Certificate of Approval to TA2 Quality and Operations Schedule for the Technical Approval of Reinforcement Continuity Systems or fully equivalent scheme.
• a valid CARES Technical Approval scheme Certificate of Approval, or fully equivalent scheme.
• a valid CARES or fully equivalent ISO 9001 Certificate of Approval.

Details of the source and suppliers shall be forwarded to the CA for agreement. Only one coupler type is to be used unless otherwise agreed by the CA. Couplers to comply with BS 8597.

Unless otherwise agreed by the CA, the mechanical coupler manufacturers shall hold a valid UKAS approved product approval certification for the manufacture and supply of coupler systems in accordance with BS 8597 and the approval bodies requirements. 

Reinforcing bars shall be adequately and appropriately prepared by the supplier to receive the agreed couplers. Unless agreed otherwise by the CA, the bar end preparation shall be conducted by firms holding a valid UKAS approved certificate for the fabrication and supply of coupler systems in accordance with BS 8597 and the approval bodies requirements.

Couplers and threads must be inspected for damage before connecting. Coupler connection must be tightened or torqued in accordance with the manufacturer’s requirements. Where on-site repair coupler systems are used the requirements of 6.1.4.2 apply and the Constructor shall ensure that the installation is as the manufacturers and approval bodies’ installation instructions.

Details of the source and suppliers shall be forwarded to the CA for agreement.

Unless otherwise agreed by the CA, the punching shear reinforcement system manufacturers shall hold:

• a valid CARES Technical Approval scheme Certificate of Approval, or fully equivalent scheme.
• a valid CARES or fully equivalent ISO 9001 Certificate of Approval.

Unless fully described in Clause P6.1.6.1, details of the proposed fibres, dosage, source and suppliers shall be forwarded to the CA for agreement.

All reinforcement should be sustainably sourced; provide an EPD or equivalent confirmation of the global warming potential of the reinforcement in kgC02e/kg.

All proprietary reinforcing bars shall be cut, bent and installed in accordance with the Manufacturer’s published information and any appropriate product technical approval.

Unless fully described in clauses P6.2.3 & P6.2.4, details of the proposed fibres, dosage, source and suppliers shall be forwarded to the CA for agreement.

All reinforcement shall be fixed in position in accordance with the reinforcement detail drawings and reinforcement schedules. Any alterations of reinforcement shall be carried out only with the prior written agreement of the CA.

All reinforcement shall be delivered in properly identified QR coded or similarly tagged bundles, reinforcement mats or pre-assembled welded fabrications and shall be stored on site in a manner so as not to become contaminated by deleterious materials or otherwise damaged. Fabric shall be stored flat.

Reinforcement shall not be dropped from height, mechanically damaged or shock loaded in any way.

All tying of steel reinforcement shall be carried out with black annealed mild steel 16 gauge tying wire, unless agreed otherwise with the CA. All ends shall be bent away from the concrete face and all loose ends shall be removed prior to placing the concrete.

The location of all welded joints shall be agreed the CA. Tack welding on site will not be permitted, unless agreed with the CA in exceptional circumstances. Provide the CA with evidence of the competence of welders and details of the welding procedures for all loadbearing welds for agreement. When welding on site ensure the welding has adequate protection from the weather. Reinforcement to be welded to structural steel shall be suitable for welding according to BS4449.

Welding procedures for on-site welding shall be agreed with the CA. Welding shall be carried out in accordance with the requirements of BS EN ISO 17660, BS 8548 and the requirements of the product approval body where applicable.

The use of pre- assembled welded fabrications must be agreed in advance with the CA.
Weld All suppliers welding reinforcement shall hold a valid UKAS product approval certificate for the welding of steel reinforcement in accordance with BS EN ISO 17660, BS 8548 and the approval bodies specific requirements.

All reinforcement ends left projecting from cast concrete shall be free of contaminants and shall be protected against damage and corrosion. Light surface rusting will be accepted, unless detrimental to the finished structure or causing rust staining to adjacent exposed concrete surfaces or formwork.

Bending of reinforcement, including straightening, at temperatures less than -5 °C is not permitted.

For proprietary purpose designed “starter bar” systems site bending is to be in accordance with the manufacturer’s recommendations.

• Bars greater than 16 diameter may not be re-bent on site.
• The curvature should be as constant as practicable.
• Bending should be in one operation at a constant rate.
• Reinforcement can be warmed but not above 100 °C.
• The bend radius shall be not less than that given in BS 8666 unless the documented re-bend properties show this can be adjusted.

A method statement must be prepared for agreement with the CA.

Inspect each bar bent for any sign of fracture. Any bars showing sign of fracture must be considered as non­- conforming.

Note: This section is for in-situ concrete post-tensioned construction.

Design shall be in accordance with:

• BS EN 1992-1-1 Eurocode 2 Design of concrete structures.
• Concrete Society Technical Report No.43 – TR43 – 3rd edition Post-tensioned concrete floors- design handbook.

Post-tensioning systems shall only be installed by specialist post-tensioning contractors that have the necessary experience, knowledge, resources, materials and equipment.

Post-tensioning contractors shall have CARES certification for the installation of post-tensioning systems in concrete structures against the relevant CARES Scheme Appendix or equivalent accredited product certification. All site post-tensioning activities including duct fixing, tendon installation, stressing and grouting shall be undertaken by suitably trained and experienced staff under the direct supervision of the post-tensioning contractor.

All post-tensioning operations shall be carried out by operatives with appropriate knowledge, training and proven experience in carrying out similar operations. Supervisors and operators shall be trained and certified to meet the requirements given in CARES Appendix PT9. Trainee post-tensioning personnel shall be adequately supervised when performing post-tensioning activities.
Personnel proposed for grouting shall be suitably experienced in such work; provide details to the CA sufficiently in advance of such work to enable experience to be reviewed.
Where required by the CA the names of all post-tensioning operatives to be employed on the site shall be submitted, with their training records before commencement of the subcontract works.

The post-tensioning contractor shall provide the CA with a quality plan giving details of all the proposed materials, equipment and method statements relating to site activities, including work instructions quality procedures, records inspection and test arrangements and work acceptance procedures.

Access to the works shall be granted to CARES for the purpose of quality auditing and maintenance of certification by arrangement with the post-tensioning contractor and/or CA.
The CA may nevertheless request an additional surveillance audit on a CARES approved post-tensioning contractor by CARES, at their own cost. If a quality audit is required by the CA during the contract then this shall be clearly stated in Clause P4.4.3.1.

The post-tensioning Designer shall calculate the theoretical tendon extension. All relevant system data shall be stated e.g. µ, k, strand E value and area, wedge draw-in on lock off and any assumed movement of dead end etc. The Post Tensioning contractor shall make available for review by the CA / Engineer the actual extensions.
However, the CA may undertake the calculations but should request the values of the necessary parameters from the post-tensioning Contractor. All relevant system data shall be stated e.g. p, k, strand E value and area, wedge draw-in on lock off and any assumed movement at dead end, etc. Extension calculations shall be submitted to the CA for acceptance at least ten working days before stressing. The CA shall confirm agreement, or comment otherwise at least five working days before stressing.

Grout shall be CARES approved to CARES Appendix PT10 or equivalent accredited product certification and comply with the performance requirements of BS EN 447:2007 Clause 6 as follows:

Grout suitability testing shall be undertaken at the commencement of the Post Tensioning installation project and will include Fluidity, Bleed, Volume change, strength, sieve test and density testing in accordance with the above.

During the grouting works the frequency of grout testing shall be as follows:

** When using a CARES approved grout and providing the grout suitability test was satisfactorily carried out at the commencement of the project, then a repeat of the bleed and volume test is not required for every grout mix. Note however, that bleed and volume testing shall be repeated at least once every 3-month period, or sooner if there is a change in grout supplier or a significant change in conditions, e.g., water supply.

To be in accordance with the relevant parts of this Specification. Where practicable provide an EPD or equivalent confirmation of the global warming potential of each element, grout/anchorage/duct, in kgC02e/kg.

Suitability tests shall be carried out with materials, plant and personnel proposed for use on site, to verify the properties in accordance with 7.2.1.6. The tests shall be sufficiently in advance of grouting operations to enable adjustments to be made to the materials, plant or personnel.
The source of materials and procedures approved as a result of satisfactory trials shall not be departed from without the approval of the CA.
Grout shall consist of pre-bagged material requiring only the addition of a measured amount of water and shall be CARES approved to Appendix PT10.
Grout shall be stored and batched in accordance with the manufacturer’s instructions.

Strand shall comply with BS 5896. The grade and diameter shall be specified by the post-tensioning Designer and shall be obtained from firm(s) holding a valid CARES Supply and Installation of Post Tensioning Systems for Concrete Structures Scheme certificate of approval for the production of prestressing steel wires and strands to CARES Appendix PT8, or fully equivalent scheme and shall be of a type that is compatible with the anchorage testing or approval.

Bar shall comply with BS 4486. The grade and diameter shall be specified and shall be obtained from firm(s) holding a valid CARES Supply and Installation of Post Tensioning Systems for Concrete Structures Scheme certificate of approval for the production of prestressing steel bars to CARES Appendix PT7, or fully equivalent scheme and shall be of a type that is compatible with the anchorage testing or approval.

The coating to unbonded strand shall be either high density polyethylene (HDPE) or high density polypropylene (HDPP). The coating thickness shall be at least 1.0mm unless otherwise stated in Clause P7.3.1.4.1 and the friction between the coating and the strand shall not exceed 60N/metre. The friction shall be determined in accordance with the test methods defined in EAD 160027 clause 2.2.33 “Monostrand, manufactured monostrand, friction between sheathing and strand”.

Anchorages for post-tensioning systems shall meet the minimum performance requirements of BS EN 13391 as defined in CARES Appendix PT3 or the post tensioning kit shall hold:

• Either a European Technical Assessment (ETA) against EAD 160004 and be CE marked.
• Or a UK Technical Assessment (UKTA) against EAD 160004 and be UKCA /UKNI marked.

Duct, vent and connection material shall be robust enough to resist damage during construction; smooth galvanised steel with a minimum wall thickness of 0.35mm, corrugated galvanised steel with a minimum wall thickness of 0.30mm, plastic ducting conforming to the requirements of fib bulletin 75 with a minimum wall thickness of 2mm, or equivalent.

Ducting shall prevent the entrance of paste from the concrete and not cause harmful electrolytic action or any deterioration of the tendon or tendon components. The internal cross-sectional area of the duct shall be at least twice the net area of the tendon’s prestressing steel.

Ducting shall be capable of transmitting forces from grout to the surrounding concrete.

A water-resistant, fabric-based adhesive tape should effectively seal any ducts. It should be suitable for application to wet galvanised steel/ plastic ducts and to be inert and non-reactive to anything in the concrete, grout or the steel, duct or strand.

All materials and components are to be stored in a safe and careful manner to ensure no damage occurs to the wires or anchors. Strand is to be stored in large diameter coils prior to installation and kept away from welding and other dangerous operations and protected from extreme changes in temperature.

Strand is to be delivered to site clean and free from permanent bends, kinks, pitting, scale or other damage and to be stored in such a way as to protect it in this condition until it is installed.

If the strand is shown to have excessive corrosion it should not be used. For clarification, unacceptable corrosion is regarded as that which cannot easily be removed by hand and permanently marks the surface of the part, such as surface pitting.

Unbonded tendons may be deviated to avoid obstructions such as openings and columns with the agreement of the CA. The change of direction of the tendon should occur away from the opening and trimmer bars should be provided to avoid any possible cracking at the corners in accordance with TR43 Clause 6.7.

Tendons shall be fixed and supported at centres not exceeding 1m and shall be securely fixed to prevent movement and flotation during the construction process.

Tendons shall be cut to length using mechanical means.

The system of tendon location marking shall be agreed with the CA.

Vents shall be fixed at injection and exit points and, where tendon drape exceeds 500mm, intermediate vents shall be fixed at tendon high points. Vents shall extend approximately 500mm above the slab surface.
All inlets and outlets shall be suitably marked to identify the tendon and their location along the tendon.
Vent spacing should not exceed 30m.

Where the tendon position is not accurately and authoritatively documented, reinforcement detection equipment must be used to locate tendon positions prior to any cutting or drilling work on the slab.

Where required, full-scale grouting trials shall be carried out using the same personnel, equipment, grouting method, materials and procedures as proposed for the Works. The trial shall demonstrate that the proposed grouting method, materials and equipment fills the ducts to the satisfaction of the CA.
Trials shall be undertaken as early as possible to allow proper inspection and any necessary modifications or adjustments. The details of the trials to be carried out shall be agreed with the CA.
The trials shall reflect the actual duct geometry and shall include typical tendon arrangements. The tendons shall be nominally stressed to ensure that they assume the proper position with respect to the ducts. Trial beams shall normally be cut at five sections for examination but more sections may be specified for complex tendon profiles.
There shall be a procedure, described in the method statement, such as backup equipment or flushing out of ducts for corrective action in the event of breakdown or blockage.
Where it is agreed that a grout trial is not necessary, prior to starting work on site, inform CARES, or equivalent, of the commencement of operations and request an audit of the post-tensioning works. Provide the CA with the outcome of the audit. Should the audit highlight any areas of concern, demonstrate to the satisfaction of the CA that any works carried out before the audit are not defective.

The jacking force should not exceed those given in the appropriate design standard and should be provided by the Post Tensioning Designer.

Stressing shall not commence before the concrete has achieved the transfer strength specified by the Post Tensioning Designer that is suitable for the equipment to be used. The concrete transfer strength shall be based on match cured cubes taken at the point of concrete placement; or another method agreed with the CA.

For routine stressing, extensions shall be measured prior to commencement of stressing, and after stressing and locking off to an accuracy of 2% or 2mm whichever is greater. Measurements shall take into consideration the possible strand movement at the dead end anchor.
The actual extensions shall be within the limits specified in BS EN 13670 Clause 7.

Tendons are not to be cut and sealed, until the Post Tensioning Designer has checked and signed off the actual extensions.
In the event that any failures occur during stressing (system components or concrete) the cause shall be thoroughly investigated and a formal report presented to the CA. No further stressing on that element shall be undertaken until the proposed corrective action has been approved by the CA

Stressing jacks and their load measuring system should have an appropriate and current calibration certificate, which is traceable to national standards, and no more than 6 months old at the time of stressing. The calibration shall be undertaken using equipment that has a UKAS verified check to standard. The stressing equipment shall be capable of establishing a tendon load to a maximum tolerance of +/-2%.

Anchorage components shall be sealed against the ingress of water or aggressive agents likely to cause corrosion of the steel or anchorage.
Unless stated in clause P7.4.7.1 the method of anchorage sealing shall be agreed with the CA.
For grouted tendons, the chosen method of sealing shall be capable of resisting the specified grout pressure.
For unbonded tendons anchorage component shall be coated with grease of similar specification to that used in the tendon and that a watertight cap be applied over the coated area. The minimum concrete end cover to the cap shall be 25mm.
Data sheets and method statements for anchorage sealing shall be submitted to the CA.

Grouting equipment shall comply with BS EN 446 clause 7.

Where necessary, all grouting and venting points shall be suitably marked to enable identification of the duct to which they are connected.
Ducts should be blown through with oil free compressed air prior to grouting, not water. Blowing through of tendons should be recorded for each tendon individually. No grout shall be placed if the temperature of the structure adjacent to the tendons is expected to be below 5°C during the following 24 hours.

Grout injection shall be continuous and shall be slow enough to avoid segregation of the grout and shall comply with BS EN 446 Clause 8.

There shall be a procedure, described in the method statement, such as backup equipment or flushing out of ducts for corrective action in the event of breakdown or blockage.

All vents shall be closed one after another in the direction of the flow. The injection tubes shall then be sealed off under positive pressure of not greater than 0.1MPa.

Grouting of the ducts shall normally be shown to leave no void which has a radial dimension greater than 5% of the maximum duct sectional dimension or which poses a risk to the integrity of the tendon. Particular attention shall be given to avoiding bleed collection or void formation at high points in the ducts or anchorages.

The filled ducts shall be protected to the satisfaction of the CA to ensure that there is no damage to the grout due to shock or vibration for 24 hours after injection of the grout.

The CA or the Constructor’s representative shall be invited to witness a representative sample of the grouting operation and countersign the grouting record sheet prepared by the Post-tensioning Contractor.

Grouting to take place as soon as practicable after the tendons have been stressed, extensions approved and the strands cropped but no longer than 28 days from stressing without the approval of the CA.

If a delay to grouting is anticipated due to conditions outside of the control of the CA, then suitable protection shall be agreed with the CA and documented.

One copy of the following records shall be sent to the CA not more than one week after each operation.

Data sheets and method statements for anchorage sealing.

1 Date of installation
2 Strand source
3 Coil number
4 Heat number, or Cast number
5 Anchorage batch number
6 Duct batch number
7 Supervisor and operatives
8 Location of the products within the structure
9 Drawing number and revision status

Records shall be available and retained for all measuring equipment used on site during the Post Tensioning installation. Such equipment includes:-

• Pressure gauges used in the grouting operation
• Pressure gauges and associated jacks in the stressing operation
• Temperature probes – certificates of conformity / manufacturer statements of accuracy are acceptable. These are typically supplied with the instrument on purchase.

All devices should have a clear identification which can be referenced against the calibration records and dates.

Unless noted concrete shall conform to BS 8500 and BS EN 206 and shall be as specified in the appropriate Project Clauses P8.2A, P8.2B, P8.2C, P8.2D & P8.2E.

The use of alternative binder systems in accordance with BSI Flex 350 is / is not permitted.

All materials permitted by BS EN 206 and BS 8500-2 can be used; products shall be produced by suppliers operating a certified factory production control system. 

The chloride content of the proposed concrete including chlorides contained in the admixtures shall be limited in accordance with BS EN 206 and BS 8500-2. Provide evidence of conformity.

Calcium chloride shall not be included in any concrete.

Provide evidence of conformity to the provisions to minimise the risk of damage by alkali-silica reaction given in BS 8500-2.

Recycled aggregate (RA) and crushed concrete aggregate (CCA) shall conform to BS 8500-2.

Admixture for consistence, water resistance, colour or other specific requirement or performance shall be in accordance with BS EN 934 and TR18 A guide to the selection of admixtures for concrete by the Concrete Society.

Water
Site addition of water is acceptable as part of approved procedure, prepared by the Producer and agreed in advance with the CA. For any other site addition of water, the concrete shall be deemed non-conforming and rejected. 

Other changes
No other changes to the fresh concrete shall be made after batching, without prior agreement of the CA.

Submit, as appropriate, details of the proposed concretes in accordance with BS EN 206 and BS 8500-1 to the CA for approval.

For each concrete mix provide an EPD or equivalent confirmation, in accordance with BS EN 15804 and BS EN 16757, of the global warming potential of the mix in kgC02e/m3.

Daily maximum and minimum atmospheric shade temperatures shall be recorded using a calibrated thermometer(s) located close to the structure.

Where required to be in accordance with BS EN 12350.

The Concrete Producer shall carry out testing of the concrete in accordance with BS EN 206 and BS 8500 and supply copies of test results to the Constructor when requested. Where the Concrete Producer identifies a non-conformity that was not obvious at the time of delivery, this shall be reported to the Principal Contractor and the CA within 24 hours of the Constructor receiving notification.

The criteria for acceptance of testing carried out by the Constructor will be those given in BS EN 206 and BS 8500.

Concrete test cubes or cylinders shall be tested in accordance with BS EN 12390 by an independent laboratory accredited by UKAS as conforming to BS EN ISO/IEC 17025 and hold a current schedule of accreditation for the required tests.

Delivery ticket information shall be in accordance with BS EN 206 and BS 8500, as relevant and shall be completed and available before discharging concrete into the structure. Where the Constructor authorises the addition of extra water this shall be recorded on the delivery ticket; see NSCS Specification Cl. 8.1.1.3. All delivery tickets shall be retained by the Constructor until the structure is handed over to the Principal Contractor or Client. Where a ticket is marked ‘non-conforming’ a copy shall be passed to both the Principal Contractor and the CA within 24 hours of placing the concrete. 

Digital tickets shall allow non-conformance to be recorded and appropriate sign off for further actions if required.

Ready-mixed concrete shall be supplied by a Producer from a plant including stand-by plants holding current accredited third-party certification meeting requirements of BS EN 206. Provide the CA with confirmation of the Producer’s certification in accordance with BS EN 206.

Details of a ready-mixed concrete plant proposed for use shall be forwarded to the CA. Contingency plans shall be in place prior to commencement of work should supplies be interrupted during a pour due to a plant breakdown. Where feasible, details of a suitable backup plant/supplier should be submitted to the CA for agreement.

For concrete from sources other than plants holding current third-party certification, submit information to the CA that the production and conformity control systems used are in accordance with BS EN 206 and BS 8500-2.

All concrete shall be supplied and transported to the point of discharge from the mixer/agitator truck in accordance with the requirements of BS EN 206 and BS 8500-2. Consideration should be given to transport distance and potential traffic conditions affecting delivery to site. Where appropriate, site located mixing plants may be considered.

To comply with BS13670 Annex F. Concrete shall be placed and fully compacted, where required, so as to avoid cold joints, honeycombing and to minimise segregation, excessive blemishes or other defect in the hardened concrete.

For concrete cast on metal decking, when noted in Clause P10.1.1.1, slabs may be cast to a specified thickness instead of a specified level.

To comply with BS13670 Annex F. Compaction, where required, shall be carried out without causing damage or displacement of the formwork, reinforcement, tendons, ducts, anchorages, inserts etc.

Self-compacting concrete may be considered in members with high reinforcement content or areas where proper compaction is difficult to achieve.

When used kickers shall be made with concrete of the same strength as that used in the wall or column, of sound construction and a minimum of 100mm high; for water-resisting construction kickers should be cast monolithically with the base structure and be a minimum of 150mm.

Suitable arrangements for premature cessation of a pour shall be agreed and in place before work starts. Should premature cessation of a pour arise, agree with the CA the extent and timing of any necessary remedial work before resumption of placing.

For concreting in cold weather if the predicted concrete surface temperature is likely to fall below freezing before the concrete has a strength of 5MPa then special measures should be taken during placing and curing.

Agree in advance with the CA any changes to the cement, admixtures or concrete temperature to limit extended stiffening times and maintain the required concrete strength development.

For concreting in hot weather, air temperature above 30°C, then special measures should be taken during placing and curing. Steel forms and reinforcement should be shaded or water sprayed to cool down the high surface temperature to avoid flash setting of concrete and early age thermal cracking.

Agree in advance with the CA any changes to the cement, admixtures or concrete temperature to minimize high temperature rises and reduction in the useful working life of the fresh concrete

For concreting in high winds special measures should be taken for protecting and curing concrete when the expected evaporation rate of water from the concrete surface is likely to exceed 1kg/m2/hr.

The Curing Class is 2 in accordance with BS EN 13670, unless otherwise specified in Clause P8.3.1.1. The surface of the concrete shall be cured to avoid premature drying out. Methods of curing shall be agreed with the CA. Curing membranes shall be compatible with any finishes to be applied subsequently.

When concrete is to be placed in conditions or in an element where early age thermal cracking is likely, measures shall be adopted that minimise the risk of early age thermal cracking to a level acceptable to the CA. Ensure that the temperature of the concrete does not exceed 70°C and that the limiting temperature drop and limiting temperature differential do not exceed the appropriate values given in CIRIA Report C766 Sections 4.2 & 4.4 and table 7.1. Where a risk of thermal cracking is identified, the location of monitoring apparatus and interpretation of the values recorded shall be agreed with the CA prior to installation.

At the end of the specified period of curing, the relevant work shall be inspected by the Constructor.

For water-resisting construction, inspection shall be carried out jointly with the Constructor and CA before backfilling or covering up to determine if there are any defects which may lead to water penetration. Further inspection shall be jointly carried out to identify any water penetration after backfilling.

Take all reasonable actions to minimise surface cracking, from all causes. Where cracking occurs that it is expected will result in corrosion of the reinforcement, unacceptable water leakage, impaired durability or reduced structural adequacy, it will be rectified as agreed with the CA.

Limits on cracking, unless specified in the Project Specification, are:

• In general reinforced concrete superstructure isolated crack widths up to 0.3mm
• In ground bearing slabs isolated crack widths up to 0.5mm between panel joints

In concrete slabs cast on metal deck formwork as part of a composite structure isolated crack widths up to 1.0 mm.

Concrete that is buried in the earth shall have a Basic finish, all other concrete shall have an Ordinary finish unless otherwise specified in the Project Specification.

The requirements for a basic finish are:

The requirements for an ordinary finish are:

The requirements for a special finish will be those for a plain finish unless modified by table P8.6.1.4

A Basic finish is to be provided unless otherwise specified in the Project Specification.

Finish requirements for different surface finishes are given in the following table:

Joints should be sawn as soon as the concrete is strong enough to be cut without damaging the arises. Unless noted on the drawings the joint depth is to be 30% of the slab thickness.

This section deals with additional considerations particular to structures partly or wholly of precast construction.

The Manufacturer shall operate an agreed quality management system to BS EN ISO 9001 with Factory Production Control in accordance with the relevant product standard unless agreed with the CA. Records of the unit mark, unit composition, date of casting, and curing regime for each precast element shall be made by the Manufacturer and kept available for inspection at the precast works.

Connection details are to be compatible with the design assumptions and should allow for the expected tolerances, in Section 10. Details are to be submitted to the CA for agreement.

An erection specification and work programme shall be prepared and agreed with the CA.

For surfaces not covered by finishes all marks shall be made so that they are hidden when unit is placed in position, or may be removed without marking the concrete surface.

As clause 8.6.1.2 an Ordinary finish is to be provided unless otherwise specified in the Project Specification; as clause 8.6.2 a Basic finish is to be provided unless otherwise specified in the Project Specification.

Precast concrete elements must conform to the requirements of Sections 5, 6, 7 & 8 of The NSCS Specification

The minimum period before removing the formwork and falsework is at the discretion of the Constructor on the basis of the assessed compressive strength of the precast element.

Delivery notes are required for all products delivered to the site.; delivery notes must show details of product conformity, as required by BS EN 13369 and the relevant product standard.

Provide an EPD or equivalent confirmation of the global warming potential of each concrete product in kgCO₂e/kg.

No precast element shall be lifted from the base on which it was cast before the concrete has attained its design demoulding strength and is strong enough to prevent the precast element from being damaged, overstressed or distorted giving regard to the demoulding equipment to be used.

Precast elements shall be clearly marked before handling in accordance with the erection specification to indicate their weight, location and orientation in the works in order to facilitate correct erection. Where delivery cannot be timed for direct final positioning, arrange suitable storage to ensure no deterioration or damage. Storage shall be on firm and uniform supports ensuring units are clear of the ground. Provide the CA with the storage proposals.

Precast elements faces to be exposed in the finished construction are to be protected from mechanical damage, dirt, staining, rust marks and other disfiguration.

The Manufacturer shall determine the need for any additional reinforcement or fittings necessary for handling their precast elements or other provisions required for temporary structural purposes until the precast elements are incorporated into the structure, including details for the making good of any provision made for lifting etc.
Any inserts or fixings required to be cast within the concrete and permanently exposed either externally or within the damp cavity of the building envelope shall be of a suitably durable material unless otherwise accepted by the CA. Any other protective treatment shall be as agreed with the CA.

Ensure that any precast concrete element to be incorporated into the structure shall be kept stable in its erected position until such time as the element can safely carry the construction loads without distress. The overall stability of the structure shall be maintained at all times during the erection process.

Are to be level and not less than the minimum recommended by the Manufacturer.

Submit proposals, agreed with the Manufacturer for products, for acceptance by the CA.

The units shall be positioned in the frame to the tolerances given in Section 10, Geometric tolerances.

All jointing to be as shown on the erection drawings and specification agreed with the CA.

Thoroughly clean and wet surfaces of precast elements, place concrete or grout, avoiding segregation, and compact thoroughly to eliminate voids. Ensure that precast elements do not move until concrete or grout has gained sufficient strength.

Thoroughly clean and wet surfaces of precast elements. Place, compact and cure in-situ concrete. Ensure that precast elements do not move until concrete has gained sufficient strength.

Grout material to comply with BS EN 197-1 and BS EN 13139.

The tolerances given in this section are NOT cumulative. Unless specifically noted as specific plus and minus deviation all values given are plus or minus.

Carry out regular checks on the structure. If an element size or position is out of tolerance propose remedial measures for agreement with the CA.

The following are the permitted tolerances for the structure as defined on the drawings. These tolerances take precedence over those given in BS EN 13670. All appropriate BS EN 13670 tolerances have been repeated for completeness of the NSCS Specification. The tolerances for position refer to the tolerance from the reference lines and datum given in Clause P1.5. Any deviation in secondary lines are included in the tolerances given. The hierarchy of tolerance adopted in the NSCs is such that the tolerance of each level must be contained within the tolerance level of the level above where 1 is the highest level:

• First – The overall tolerance of the structure, Cl. 10.2, 10.3 and 10.4
• Second – The positional tolerance of all parts of elements of the structure within the overall tolerance, Cl. 10.5 and 10.6
• Third – The dimensional tolerance of the individual elements within their positional tolerance, Cl. 10.7, 10.11 and 10.12
• Fourth – The position tolerance of reinforcement and fixings within the individual elements dimensional tolerance, Cl. 10.8, 10.9 and 10.10

Slabs cast on metal decking are to have: a constant thickness in accordance with 10.7.1 / a finished level in accordance with 10.9.1.

BS EN 13670 defines normal tolerances as Class 1 and this sets minimum limits for structural safety. The NSCS tolerances given in this section are Class 2.

Any project variations to meet requirements of the construction method, design, fit requirements or any other reason shall be considered Class 3 and the required deviations are given in the Project Specification.

Class 3 tolerances specified in Clause 10.13 may apply to the whole structure or any part.

Where Class 3 tolerances are given in the Project Specification the execution will be to Execution Class 3.

The tolerances given in Cl. 10.2.2, 10.6.5, 10.6.6 & 10.9.1 below apply before the striking of the formwork. The tolerances given are before deformation caused by loading and time-dependent effects. Floor levels and the floor flatness shall be checked on a 3m by 3m grid.

The ‘box principle’ can be applied to the tolerances in the NSCS Specification. Where it is applied to the whole building the tolerances is as given by Cl. 10.2.1; where it is applied to an individual element the tolerance is± 20 mm.

The ‘box principle’ can be applied to the tolerances in the NSCS Specification. Where it is applied to the whole building the tolerances is as given by Cl. 10.2.1; where it is applied to an individual element the tolerance is± 20 mm.

Location of any column, wall or floor edge, at any storey level, from any vertical plane through its intended design centre at ground floor level in a multi-storey structure.

Permitted deviation Δ = the smaller of 50mm or H/(200n^1/2) mm

where h = free storey height in mm

H = free height at location = Σh_i in mm

n = number of storeys where n > 1

Level of floors at supports measured relative to the intended design level at the level being checked.

Permitted deviation D for

H < 10m =15mm

10 m < H < 100 m =0.5(H + 20) mm H > 100 m =0.2(H + 200) mm

where H = sum of the intended storey heights in m

Base supports shall include direct foundations and pile caps, etc. but not deep foundations such as piles, slurry walls, diaphragms, special anchorages, etc.

Permitted deviation Δ = 25 mm

where l_x = intended position in the x direction

l_y = intended position in the y direction

Position in the vertical direction of a base support relative to the intended design position.

Permitted deviation Δ = 20mm

where supporting concrete superstructure

Permitted deviation Δ = -15mm+ 5mm where supporting steel superstructure

where h = intended distance of foundation below datum level

Note: Deviations are coordinated with BS EN 1090-2: 2008 Cl. D.2.20.

• Distance of centre of a bolt group from intended design position Permitted deviation = 6 mm
• Location of bolt at tip, from centre of bolt group Permitted deviation Δ_Y, Δ_X = 10 mm
• Protrusion

Permitted deviation Δ_P. : -5mm > Δ_P <25mm

• Distance of centre of a bolt group from intended design position Permitted deviation = 3 mm
• Location of bolt at tip, from centre of bolt group Permitted deviation Δ_Y, Δ_X = 3 mm
• Vertical protrusion Permitted deviation Δ_P. : -5mm > Δ_P <45mm
• Horizontal protrusion Permitted deviation Δ_X. : -5mm > Δ_X <45mm

The deviation or sum of any deviations of any individual element must not exceed the overall building structure tolerance given in 10.2

Position of the element edges and centre line relative to:

• At base level the intended design position.
• At any upper level the actual location of the element at the level below.

Permitted deviation Δ =10mm where L = distance to centreline from grid line

Inclination of a column or wall at any level in a single- or multi-storey building.

Permitted deviation Δ for

h <: 10 m = the larger of 15mm or h/400 h > 10 m = the larger of 25mm or h/600

where h = height of element in mm

Deviation between centrelines at floor level.

Permitted deviation Δ = the larger of 10mm or t/30 mm, but not more than 20mm where t = thickness in mm = (t1 + t2)/2

Curvature of an element between adjacent storey levels.

Permitted deviation Δ for

h <: 70 m = the larger of 15mm or h/400 h > 10 m = the larger of 25mm or h/600

where h = height of element in mm

Level of adjacent floors at supports.

Permitted deviation Δ =10mm where h = storey height in mm

Dimension of free space between adjacent columns and walls.

Permitted deviation Δ = the larger of 20mm or L/600 but not more than 40mm, where L = distance between the elements in mm.

Location of a beam to column connection measured relative to the column.

Permitted deviation Δ = the larger of 20mm or b/30mm

where b = dimension of column in the same direction as Δ in mm

Position of bearing axis of support when structural bearings are used.

Permitted deviation Δ = the larger of 15mm or L/20mm

where L= intended distance from edge in mm

Horizontal straightness of beams.

Permitted deviation Δ = the larger of 15mm or L/60mm

where L= distance between supports

Distance between adjacent beams, measured at corresponding points.

Permitted deviation Δ = the larger of20mm or L/600mm, but not more than 40mm

where L = distance between support centrelines in mm

Difference in level across a beam or slab at corresponding points in any direction.

Permitted deviation Δ = (10 + l/ 500) mm

where L= span of element in mm

Level of adjacent beams, measured at corresponding points.

Permitted deviation Δ = (10 + L/500) mm

where L = distance between support centrelines in mm

• At base level position of slab edge relative to intended design position.
• At upper levels position of slab edge relative to actual slab edge position on the floor below.

Permitted deviation Δ = 10 mm

Applicable to beams, slabs, columns and other elements covering length, breadth and depth.

Permitted deviation Δ = for

l < 150 mm = 10mm I = 400 mm = 15mm I > 2500mm = 30mm

with linear interpolation for intermediate values where 11, 12 = intended dimensions

Applicable to beams, slabs, columns and other elements.

Permitted deviation Δ = the larger of 10mm or L/25mm, but not more than 20mm where L= length in mm

The tolerance of cover to reinforcement within an element.

Permitted deviation Δ_(plus) for

h < 150 mm = +10 mm

h = 400 mm = +15 mm

h>: 2500 mm = +20 mm

with linear interpolation for intermediate values

Permitted deviation Δ_(minus) = 10mm

where c_min = required minimum cover

c_nom = nominal cover given on drawings

Δ = permitted deviation from c_nom

h = height of cross section

For foundations and members in foundations, permitted plus-deviations may be increased by 15mm Minus­ deviations are 15mm cast against blinding or prepared earth and 50mm when cast directly against earth faces.

Permitted minus-deviation Δ = 0.06L mm

where L = intended lap length in mm

• Anchorages
  Permitted location deviation Δ = 25mm horizontally 5mm vertically

• Tendons
  Permitted deviation Δ Horizontally
  in beams = 0.03h {width) > 5mm< 30mm
  in slabs = 150mm
  Vertically Δ_(plus) If h < 200mm = +h/40
  If h > 200mm = +15mm
  Δ_(minus) all h = -10mm
  where h for vertical section = depth in mm
  h for plan section= width in mm
  y = intended location in mm

Flatness of surface of any element. Finish type as table 8.6.1 or 8.6.2

• Basic unformed surface
  Permitted global deviation = 15mm
• Ordinary unformed surface as SR3
  Permitted global deviation Δ = 10mm
  Plain unformed surface as SR2
  Permitted global deviation Δ = 5mm
  Special unformed surface as SR1
  Permitted global deviation Δ = 3mm
• Ordinary formed surfaces
  Permitted global deviation Δ = 9mm Permitted local deviation D = 5 mm
• Plain formed surfaces
  Permitted global deviation D = 9mm Permitted local deviation D = 3 mm

Flatness of surface of any element; where the global deviation D is measured under a 2m long straight edge and the local deviation D is measured under a 200mm long straight edge.

• Basic unformed surface
  Permitted global deviation = 15mm

• Ordinary unformed surface as SR3
  Permitted global deviation Δ = 10mm

• Plain unformed surface as SR2
  Permitted global deviation Δ = 5mm

• Special unformed surface as SR1
  Permitted global deviation Δ = 3mm

The global deviation D is measured under a 2m long straight edge

Straightness of edge of floor slab or element.

Permitted deviation Δ for

L < 1 m = 8 mm L > 1 m = 8 mm/m, but no greater than 20 mm

where L = length of edge

Size and location of opening relative to actual location of element.

Position
Permitted deviation Δ₁ = 10 mm, where L₁ = intended distance to centre line
Size
Permitted deviation Δ₂ =
L₂ < 150mm = 6 mm
L₂ = 400mm = 15 mm
L₂ > 2500mm = 30 mm
with linear interpolation for intermediate values, where L₂ = intended dimension

Location of fixing or groups.

• Location of fixing or groups relative to either the intended design position at the base level, or the actual position of the element they are cast into at any upper level. Permitted deviation Δ₁ = 6mm where L₁ = distance between bolt groups
• Internal distance between fixings in a group relative to the intended design distance. Permitted deviation Δ₂ = 3mm where L₂ = distance between bolts

Protrusion of fixing

Permitted deviation = Δ_(plus) + 25 mm, Δ_(minus) – 5 mm

Location of channels

• Location of edge of channel relative to either the intended design position at the base level, or the actual position of the element they are cast into at any upper level.
  Permitted deviation Δ1 = 10mm
• Length of channel relative to the intended design distance
  Permitted deviation Δ2 = 10mm
• Protrusion of fixing

Permitted deviation Δ1 = 5 mm
Inclination Δ2 = 5 mm

Location of fixing or groups relative to either the intended design position at the base level, or the actual position of the element they are cast into at any upper level.

• Deviation in plane
  Permitted deviation Δ1 = 10 mm
• Deviation in depth
  Permitted deviation Δ2 = 10 mm

Note: Deviation in plane can be to a vertical or horizontal surface.

The permitted deviation in the height of any riser is 5mm of the intended design value. The permitted deviation in the length of any going is 5mm of the intended design value.

Standard precast products shall comply with the tolerances given in the relevant product standards.

Concrete elements produced for the project shall comply with the tolerances for: sections of elements; position of reinforcement within elements; surface straightness; and openings and fixings given above.

Unless otherwise agreed the width of joints between units shall not be more than 10mm.