When something goes wrong with a building, the first instinct is usually to blame the builder. Sometimes the builder built exactly what was drawn, and the problem is the design. Sometimes it is both. This guide explains how the law approaches that question for homeowners and small businesses in England and Wales. Claims against builders for poor work are covered in the builder disputes series.
Two different obligations
A builder's contract is to carry out the work. A consumer's contract with a trader includes a term that the trader "must perform the service with reasonable care and skill" (Consumer Rights Act 2015, s.49). The builder is also bound by whatever the contract says about materials, standards and following the drawings.
An architect or engineer engaged to design owes a duty to design with the reasonable skill and care of a competent member of the profession: see what a claim involves. Where the appointment also covers inspection during the build, there is a separate question of whether they should have spotted the builder's mistakes: see inspection and certificates.
Where design ends and workmanship begins
The courts accept the boundary is not always clear. In Robinson v P E Jones (Contractors) Ltd [2011] EWCA Civ 9, the Court of Appeal noted that in an earlier case May LJ had observed "that the borderline between design work and construction work was blurred".
Two examples from reported cases show how it is drawn:
- In McGlinn v Waltham Contractors Ltd [2007] EWHC 149 (TCC), the judge rejected a complaint that the architect should have specified the sealant for windows. The claimant's own architectural expert accepted that, by reference to the British Standards, "the choice of window sealant is regarded as a workmanship issue, rather than a matter of design", and the judge said that "A reasonably competent architect would not specify the precise make or type of sealant to be used".
- In Vainker v Marbank Construction Ltd [2024] EWHC 667 (TCC), the architect specified a damp-proof course set back from the face of the brickwork. The judge held this was a negligent error which, "Irrespective of any defects in construction", provided a means for water to enter and soak into the brickwork.
So the questions an expert usually asks are: was the work built as drawn and specified; if it had been built exactly as designed, would the defect still have happened; and was the point left to the builder's judgement or fixed by the design?
When the builder followed a flawed design
For work on a dwelling, section 1 of the Defective Premises Act 1972 requires a person taking on the work to see that it is done "in a workmanlike or, as the case may be, professional manner, with proper materials" and so that the dwelling is fit for habitation. The duty is owed by "a person taking on work for or in connection with the provision of a dwelling", and the reference to a "professional manner" indicates that it reaches design and other professional work as well as building.
Section 1(2) gives a builder some protection: a person who does the work properly "in accordance with those instructions" is treated as having discharged the duty, "except where he owes a duty to that other to warn him of any defects in the instructions and fails to discharge that duty". Section 1(3) adds that a person is not treated as having given instructions "merely because he has agreed to the work being done in a specified manner, with specified materials or to a specified design". Section 2A, added by the Building Safety Act 2022, applies equivalent rules to work on existing dwellings completed after 28 June 2022.
Design and build
On some projects the builder takes on the design as well, either for the whole job or for parts of it, such as a specialist roof or a steel frame designed by the supplier. Who carries the design risk then depends on the contracts. The appointment, the building contract and any design responsibility schedule are the documents that answer it.
When both are to blame
If the architect and the builder are each liable for the same damage, each can be sued for it. The Civil Liability (Contribution) Act 1978 then lets "any person liable in respect of any damage suffered by another person" recover contribution "from any other person liable in respect of the same damage" (s.1(1)). The court fixes the contribution at what is "just and equitable having regard to the extent of that person's responsibility for the damage in question" (s.2(1)). A claim for contribution has its own two-year time limit (Limitation Act 1980, s.10).
This matters most when the builder has gone bust. If the architect is liable for the whole of the damage, the homeowner can recover from the architect, who is left to claim contribution from an insolvent builder. See also when the builder has gone bust or disappeared.
Net contribution clauses
Many professional appointments contain a net contribution clause, which limits the professional's liability to the share that is fair given their responsibility, on the assumption that the others responsible have paid theirs. In West v Ian Finlay & Associates [2014] EWCA Civ 316, homeowners claimed against their architect over a refurbishment in which the main contractor, also responsible for some of the losses, was insolvent. The Court of Appeal held that the clause applied, that it was not unfair under the consumer regulations then in force and that it satisfied the reasonableness test in the Unfair Contract Terms Act 1977, noting among other things "the prevalence of the usage of the NCC in standard RIBA forms". The effect was to place the risk of the contractor's insolvency on the homeowners.
The Court also said it "would have been preferable" for the architect to have drawn the clause to the clients' specific attention. West was decided under the Unfair Terms in Consumer Contracts Regulations 1999. Consumer contracts made since 1 October 2015 are governed by Part 2 of the Consumer Rights Act 2015, under which an unfair term "is not binding on the consumer" (s.62(1)). Whether a particular clause is fair depends on its wording and the circumstances.
What a solicitor will want from you
- The architect's or engineer's appointment, including any limitation or net contribution clause.
- The building contract, and any document allocating design responsibility.
- The drawings and specification as issued for construction, with revisions and dates.
- Photographs of the defect and of the work as it was built, if you have them.
- Any expert report on whether the defect is one of design, workmanship or both.
- What you know about the builder's current position: trading, insolvent or uncontactable.
This guide is general information about the law of England and Wales. It is not legal advice. Whether a defect is a design or a workmanship problem is usually a question for expert evidence, and different time limits can apply to the claims against each party.
Frequently asked
How do I know whether a defect is a design fault or a building fault?
Usually through expert evidence. If the work was built as drawn and specified and still failed, that points to the design. If it departs from the drawings or specification, or was carried out poorly, that points to the builder. The line can be blurred, and some matters, such as the choice of a particular sealant, may be treated as workmanship rather than design.
The builder says they just followed the drawings. Is that a defence?
For dwellings, the Defective Premises Act 1972 treats a builder who does work properly in accordance with instructions as having met its duty under that Act, unless it owed a duty to warn of defects in the instructions and did not. A client who merely agrees to the work being done to a specified design is not treated as having given instructions for this purpose. The builder's contract may also contain its own obligations.
Can I claim against both the architect and the builder?
Yes, where both are responsible for the same damage. Under the Civil Liability (Contribution) Act 1978 each can then claim a contribution from the other, in the share the court finds just and equitable. A net contribution clause in the architect's appointment can limit the architect to its own fair share.
What is a net contribution clause?
A term in a professional's appointment limiting their liability to the share of the loss that is fair given their responsibility, on the assumption that others responsible have paid their share. In West v Ian Finlay & Associates the Court of Appeal upheld one in an architect's appointment, which meant the homeowners bore the risk of the insolvent contractor's share.