The JCT Design and Build Contract (DB) is one of the most common forms used in UK construction where the contractor takes on responsibility for both design and construction. It is a single-point-of-responsibility structure: the contractor is liable for design defects as well as workmanship, and the employer's design risk is reduced. In return, the contractor typically charges a higher contract sum and seeks to limit design liability through Schedule 3 amendments. Where DB contracts go wrong is in the interface between the Employer's Requirements (what the employer wants) and the Contractor's Proposals (what the contractor offers). When these documents conflict, the contract has a precedence rule — but the rule is often modified by amendment, and the modification can shift surprising risk back to the employer. Schedule 3 amendments and the precedence regime should be reviewed line by line.
What is a JCT Design and Build?
A JCT Design and Build Contract is a standard form construction contract published by the Joint Contracts Tribunal, currently in the 2024 edition. It is used where the contractor undertakes to complete the design and the construction. Key documents include: the Articles of Agreement, the Contract Particulars, the Conditions, the Employer's Requirements, the Contractor's Proposals, and Schedule 3 (amendments). The contract operates within the framework of the Housing Grants, Construction and Regeneration Act 1996 (as amended) for payment and adjudication.
Red flags to watch for
Under common law, design and build contractors typically owe a fitness-for-purpose obligation — the design must achieve the employer's stated purpose. A clause limiting liability to reasonable skill and care (the architect's standard) can leave the employer without a remedy if the building fails to perform as intended despite no negligence in the design process. JCT DB 2024 leaves this open to negotiation in Schedule 3.
A net contribution clause limits the contractor's liability to its proportionate share of fault, with sub-consultants jointly liable for the rest. For the employer, this can mean having to chase multiple parties to recover full loss. Whether this is acceptable depends on the financial covenant strength of all parties.
Design liability caps are common — typically 10–20% of the contract sum or aggregate insurance limits, whichever is lower. For a £20m project, a 10% cap leaves the employer recovering only £2m for a design defect that could cost £10m to remediate. The cap should be sized against realistic worst-case design failures.
Tenants, funders, and purchasers typically need collateral warranties or third-party rights from the contractor and key sub-consultants. A DB contract that limits collateral warranty obligations — or charges fees for them — can compromise the project's commercial viability. The Contracts (Rights of Third Parties) Act 1999 provisions in JCT DB 2024 should be reviewed.
Following Cavendish Square Holding BV v Talal El Makdessi [2015] UKSC 67, liquidated damages must protect a legitimate interest and not be exorbitant. LDs that are far above the employer's likely loss can be challenged as a penalty. Conversely, LDs set unreasonably low can be used by the contractor to delay strategically.
Section 108 of the Housing Grants, Construction and Regeneration Act 1996 gives every party the right to refer any construction dispute to adjudication at any time. A clause attempting to restrict adjudication to specific dispute categories is contrary to the Act and unenforceable, but can deter parties from exercising the right.
Your legal rights
UK parties to JCT design and build contracts are protected by: the Housing Grants, Construction and Regeneration Act 1996 (as amended by the Local Democracy, Economic Development and Construction Act 2009), particularly s 108 (adjudication), s 110 (payment notices), s 111 (pay less notices), s 112 (right to suspend for non-payment), and s 113 (pay-when-paid prohibited); the Scheme for Construction Contracts (England and Wales) Regulations 1998 (SI 1998/649); the Defective Premises Act 1972 (now extended to 30 years for new dwellings under the Building Safety Act 2022); the Construction (Design and Management) Regulations 2015 (SI 2015/51); the Building Safety Act 2022 (for higher-risk buildings); and Contracts (Rights of Third Parties) Act 1999. Disputes can be adjudicated, arbitrated, or litigated in the Technology and Construction Court (TCC).
Questions to ask before you sign
- 1Is the contractor's design liability fitness for purpose or reasonable skill and care, and what insurance backs it?
- 2What is the design liability cap as a percentage of contract sum, and is it adequate for realistic remediation cost?
- 3What collateral warranties or third-party rights are included for tenants, funders, and purchasers?
- 4How are conflicts between the Employer's Requirements and the Contractor's Proposals resolved?
- 5Are liquidated damages sized as a genuine pre-estimate of loss, and what is the rationale?
- 6What Schedule 3 amendments have been made, and what is the cumulative effect on risk allocation?
Disclaimer: This guide is for educational purposes only and does not constitute legal advice. Contract law varies by jurisdiction and individual circumstances. Always consult a qualified legal professional before making decisions based on this information.