If the architect I hired makes a mistake in the design, what can I claim?

What you can claim

• The cost of redoing or correcting the design, or a refund of the fees if it is of no use to you.
• The extra cost of the building work caused by the mistake, such as demolishing and rebuilding what was built wrongly or adapting it. What a properly designed building would have cost anyway is not normally compensated, because it had to be paid in any case. For example, if the design left out a necessary reinforcement, what is compensated is the extra cost of adding it late, not what it would have cost to include it from the start.
• The losses caused by the delay, such as what you fail to earn, which is the loss of profit (“lucro cesante”), for example the rent from a flat you could not let in time.
• Fines and expenses caused by a design that does not comply with planning rules, for example if planning permission is refused.
• Physical damage that appears in the building later on.

For all of this you need a report from another architect explaining the mistake, its consequences and what it costs to put right. Before correcting anything, make a record of the state of the building work.

The routes for claiming and their time limits

• Under the contract. The architect is liable for not having carried out the engagement properly. The time limit is in principle ten years if the contract is governed by Catalan law and five in the rest of Spain, from when you become aware of the mistake and the damage.
• Under the Building Act, if the work is of a kind it covers, such as a new house or renovation work that changes the structure, the volume or the use of the building. The handover of the works is when the builder hands the work over to the developer and the developer accepts it. It is normally done in writing, in a handover certificate. From the handover, the architect is liable for physical damage that appears within ten years if it affects the structure, or within three if it affects habitability, such as damp or insulation. Once the damage appears, there are two years to make a claim. The architect is also liable for calculations commissioned from other technical professionals. If the work was supervised by another architect, that architect is equally liable for the defects in the design and can then recover the cost from the architect who drew it up.
• If the work was never completed. In 2026 the “Tribunal Supremo”, Spain's Supreme Court, confirmed that the architect is still liable for errors in the design and in the supervision of the work even if the work was left unfinished and never handed over. The architect is also liable for signing a final completion certificate, the document declaring the work finished, that did not reflect reality.

The contractual route and the statutory route can be pursued at the same time.

How to claim

• Make a written claim against the architect and their insurer, both the current one and the one they had before. In Catalonia the architect is obliged to have liability insurance or an equivalent guarantee and to tell you who their insurer is.
• If the contract limits their liability to the amount of their fees, that clause may not be valid. In 2026 the Supreme Court confirmed that one such clause used by a law firm was void and its reasoning may also apply to architects.
• If the design bears the “visado” of the Architects' Association (“Colegio de Arquitectos”), which is a check of its formal aspects, the association is only liable if the architect does not pay and only for the defects it should have spotted when issuing the visado.
• Before suing, you must try to negotiate, as the law has required since 2025.