Construction Contracts for Luxury London Renovation: JCT, NEC, and Protecting the Client's Position

Most clients who renovate a prime London property for the first time encounter the construction contract as a stack of papers they are asked to sign before work begins. They may read it partially, understand it partially, and sign it with a vague sense that their solicitor should probably have reviewed it. This is not the appropriate approach to a document that will govern a transaction worth several hundred thousand to several million pounds and that will be the decisive reference if any significant dispute arises.

The construction contract is not boilerplate. It is a negotiated legal document whose terms directly affect the client's exposure to risk — from cost overruns, programme delays, defects, contractor insolvency, and disputes. A client who understands its key terms is a client who can negotiate them intelligently, administer them correctly, and invoke them effectively when needed.

The Principal Contract Forms

JCT (Joint Contracts Tribunal): The dominant contract family for UK residential and commercial construction. JCT produces a suite of contract forms for different project types and procurement routes.

*JCT Minor Works Building Contract (MW)*: Appropriate for simple projects up to approximately £250,000–£400,000. Shorter document, less procedural complexity, but fewer protections for the client than the more comprehensive forms.

*JCT Intermediate Building Contract (IFC)*: Appropriate for moderate-complexity projects from approximately £200,000 to £1,500,000. A balance between procedural rigour and administrative burden.

*JCT Standard Building Contract (SBC)*: The full-form JCT contract, appropriate for complex projects above £500,000. Comprehensive provisions for design responsibility, variations, extensions of time, loss and expense claims, and dispute resolution. The SBC with Quantities (SBC/Q) is used where a Bill of Quantities is the pricing mechanism; SBC without Quantities (SBC/XQ) where a specification and drawings form the basis.

*JCT Design and Build Contract (DB)*: Used where the contractor holds design responsibility as well as construction responsibility. Appropriate for design-and-build procurement.

For most prime London renovations in the £500,000–£3,000,000 range with a traditional procurement route (separate design team, contractor building from drawings and specifications), JCT IFC or JCT SBC are the appropriate forms.

NEC4: The NEC suite (originally the New Engineering Contract) is widely used in public sector and infrastructure procurement. Its collaborative, early-warning-focused approach is appealing philosophically but requires both parties to have significant contract administration experience to work correctly. Less commonly used in prime residential renovation than JCT.

Bespoke contracts: Some large contractors operate with their own bespoke contract forms. These should be reviewed carefully — bespoke contractor-drafted contracts almost always favour the contractor. A client's solicitor or quantity surveyor should review any bespoke form and advise on terms to negotiate before signing.

Key Contract Terms: What to Negotiate

Contract sum and pricing basis:

The contract sum is the price the contractor will charge for carrying out the specified works. It can be established in different ways:

*Lump sum*: The contractor prices the complete specified works for a fixed sum. Variations (additions or changes to the scope) are priced separately. This provides the best cost certainty for the client provided the specification is complete and clear. It places the risk of estimating errors on the contractor — if the contractor has underpriced an item, the lump sum is still the contract sum.

*Remeasurement (Bill of Quantities)*: The contract sum is established by applying agreed unit rates to measured quantities. If the actual quantities differ from those billed, the contract sum adjusts accordingly. Used where the scope of some elements cannot be defined precisely at tender — basement excavation in uncertain ground conditions, for example, where the exact depth cannot be confirmed until work begins.

*Cost-plus (or prime cost plus fee)*: The client pays the contractor's actual costs plus a fixed fee or percentage for overhead and profit. Maximum cost transparency but minimum cost certainty — the total is not known until the project is complete. Appropriate only for emergency or highly uncertain works; not for a well-defined renovation.

Variations:

Variations — changes to the specified works instructed after the contract is formed — are the most common source of cost overruns and disputes in residential renovation. The contract should specify: - Who can instruct variations (the architect or contract administrator; not the client directly unless specified) - The process for pricing variations (submission of quotation before work commences, agreed and confirmed in writing) - What constitutes a variation vs. an error in the contractor's own estimation (contractor errors are not variations)

The discipline of pricing variations before instructing them — rather than proceeding and pricing later — is the most important cost control behaviour in a renovation project. A variation priced after the work is done gives the client no leverage; a variation priced before instruction can be negotiated, rejected, or redesigned.

Programme and extensions of time:

The contract programme sets out the agreed sequence and duration of the works. The contract should include:

• —A master programme issued at contract start, showing all activities and their durations
• —A mechanism for the contractor to claim extensions of time for events that are not their fault (employer variations, exceptionally adverse weather, statutory utility delays)
• —A mechanism for the client to claim liquidated damages for delays that are the contractor's fault — a pre-agreed daily or weekly sum that compensates the client for the loss caused by late completion without requiring them to prove actual loss

Liquidated damages (LD) provisions are often omitted from residential contracts because the client does not insist on them. They are among the most valuable client protections in the contract and should always be included at a rate that reflects the genuine cost of delayed occupation (alternative accommodation, storage, additional finance costs).

Payment terms:

JCT contracts provide for monthly interim valuations — the contractor submits a valuation of the work carried out, the contract administrator certifies the amount properly payable, and the client pays within the specified period (typically 14–28 days). The contract should specify:

• —Interim payment dates and the notice periods for payment and pay-less notices
• —The retention percentage (typically 5%, held against defects)
• —The final account process — how the final contract sum is established after all variations are agreed

UK construction payment legislation (the Housing Grants, Construction and Regeneration Act 1996, as amended) sets minimum requirements for payment notice and pay-less notice periods in construction contracts. Any contract that attempts to exclude these rights is unenforceable.

Defects liability:

The defects liability period (or rectification period under JCT SBC) is the period after practical completion during which the contractor is obliged to return and rectify notified defects without additional charge. Typically 12 months in JCT IFC and SBC. The client retains the second-half retention until the defects have been made good and the final certificate issued.

Dispute resolution:

JCT contracts provide for adjudication as the first-resort dispute resolution mechanism — a statutory right under the HGCRA 1996. An adjudicator's decision is binding unless overturned by arbitration or litigation. Adjudication is relatively fast (decision within 28 days of appointment) and relatively cost-effective — appropriate for disputes over specific issues (a specific variation, a specific defects claim).

For large or complex disputes, arbitration (binding, private, expert-judge) or litigation (courts) provide more thorough processes at greater cost and time.

Insurance Requirements

The contract should specify the insurance obligations of each party:

Contractor's All Risks (CAR) insurance: The contractor's insurance covering the works in progress against loss or damage. Typically maintained by the contractor and included in the contract sum. The client should verify that the policy is in place and adequate before work begins.

Contractor's liability insurance: Public liability and employer's liability insurance covering the contractor's legal liability for injury to third parties and to their employees. Minimum £5m public liability is standard; some clients require £10m for high-value projects.

Professional indemnity (PI) insurance: The design professionals' insurance covering their legal liability for negligent design or advice. The architect, structural engineer, and M&E engineer should each have PI insurance in place for the duration of the project and for the appropriate run-off period after completion.

Existing structures insurance: Where the works are on an existing occupied or unoccupied building, the client's building insurance should be notified that renovation works are in progress. Standard building insurance may be voided if major works are carried out without notification. A specific building works policy or an endorsement to the existing policy should be in place.

Contractor Insolvency

Contractor insolvency during a project is uncommon but not rare — particularly in the post-Covid environment of material price volatility and thin contractor margins. The contract provisions relevant to insolvency:

Step-in rights: JCT contracts allow the client to terminate the contract on contractor insolvency and appoint a replacement contractor. The original contractor's insurers and sub-contractors are typically notified.

Performance bond: A performance bond is a guarantee from a surety (typically an insurer) that pays the client a defined sum (usually 10% of the contract value) if the contractor defaults. Performance bonds are not standard in residential renovation contracts but can be negotiated for larger projects or with contractors whose financial strength is uncertain.

Vetting the contractor: The best protection against insolvency risk is selecting a financially stable contractor in the first place. Request the last two years of audited accounts from tenderers; check Companies House for any County Court Judgements or adverse filings; speak to references from previous clients about payment behaviour with sub-contractors.

The ASAAN Approach to Contracting

ASAAN operates under JCT forms of contract for all projects above £200,000, using IFC for mid-range projects and SBC for larger commissions. We welcome client review by their solicitor or quantity surveyor; we do not use bespoke contract forms that exclude statutory rights.

We price variations before proceeding with them, maintain a live variation register, and report the forecast final account position monthly. Our clients are never surprised by the final account — because we manage cost transparency as a discipline throughout the project, not as an afterthought at completion.