Common Architect & Engineer Negligence Claims
Design Liability vs Site Supervision Liability
An architect or engineer's duties depend on the scope of their appointment:
- Design-only appointment — the professional is responsible for the design and specifications, but not for how the contractor builds or for the quality of workmanship. Defects caused by the contractor departing from the design are the contractor's liability, not the designer's. However, where the design itself is defective — structurally, aesthetically, or in terms of regulatory compliance — the designer is liable for the consequences.
- Full service appointment (design and supervision) — under a full RIBA Plan of Work appointment, the architect supervises the works throughout all work stages and certifies payment applications. A negligent architect who fails to identify departing workmanship during site inspections, or who certifies defective work, is liable for the resulting defects to the extent they should have been identified on reasonable inspection.
- Novated appointment — where a design-and-build contractor has the architect novated to them, the architect owes duties to both the employer and the contractor. The scope of the novated duty requires careful analysis — a specialist solicitor identifies the correct defendant and the correct scope of duty in novated appointment claims.
Frequently Asked Questions
The architect says the defects are the builder's fault — not their design. What can I do?
This is a common response — and it may be partially correct. A detailed independent investigation is essential to establish the cause of the defects: whether they result from defects in the design (architect's liability), defects in workmanship (contractor's liability), or both. An independent architect and structural engineer expert assess the design against the construction to determine responsibility. Where the defect arises from the design being incapable of producing the intended result even if built correctly, the designer is liable. Where the defect arises from the contractor departing from a competent design, the contractor is liable. Where a supervising architect failed to identify the departure during site inspections, both may be liable jointly.
My planning application was refused — can I claim against the architect who prepared it?
Possibly — where the architect prepared a planning application that was clearly contrary to development plan policy or obviously incompatible with the site's planning constraints, and failed to advise the client of the realistic prospects of success, the architect may be liable for the abortive costs of the application (fees, planning consultant costs, and any wasted design costs). However, a refusal is not itself evidence of negligence — planning decisions involve a degree of judgment and uncertainty, and no competent architect can guarantee success. The question is whether the advice on prospects and the quality of the application met the standard of a reasonably competent architect experienced in planning.
The architect says their design was approved by building control — does that protect them?
Not conclusively — building control approval confirms that the design was compliant with the Building Regulations at the time of approval, but it is not a guarantee that the design was otherwise competent or that it met all the functional requirements of the building and the client's brief. Where the design complied with minimum Building Regulations standards but was nonetheless negligent — for example, producing unworkable M&E systems, inadequate sound insulation beyond Part E minimums, or structural elements technically within regulations but incapable of performing their function — the approval does not protect the architect. An independent expert assesses whether the design met the standard of reasonable care and skill beyond minimum regulatory compliance.
Do I need to sue the architect or the engineer — or both?
It depends on the cause of the defects. Where the defect arises from architectural design (layout, envelope, aesthetics, function), the architect is the correct defendant. Where it arises from structural or M&E engineering design, the relevant engineer is the defendant. Where multiple design professionals contributed to the defect — for example, the architect specified inadequate acoustic separation and the M&E engineer specified undersized ventilation — both may be joined as co-defendants. A specialist solicitor analyses the cause of each defect, identifies the correct defendant for each, and pleads accordingly — often working with an expert team covering architecture, structural engineering, and M&E.
What professional indemnity insurance are architects and engineers required to hold?
ARB-registered architects must hold professional indemnity insurance as a condition of registration — the minimum level is determined by the RIBA Code of Practice but is commonly £250,000 to £5m+ per claim depending on firm size and project scale. Chartered engineers registered with the ICE or IStructE are required to hold PI insurance as a condition of their membership of the relevant institution. PI insurance means claims are typically made against the professional's insurer — a well-resourced defendant who will instruct specialist PI solicitors to defend the claim. Claimants need equivalent specialist representation.