Buying & selling

Hidden Defects When Buying a Property: How to Claim

They appear after the purchase and can cost a fortune. We explain what they are, who is liable and how to claim.

Buying & selling · Updated January 2026 · 5 min read

Hidden defects are serious property faults that were not visible at the time of purchase and that make it unfit for use or reduce its value: aluminosis, structural damp, illegal installations, pests…

Who is liable?

The seller is liable for hidden defects even if unaware of them, within the legal period set by the Civil Code. If they knew and concealed them, liability is greater.

How to claim

Document the defect (technical report, photos, repair quotes).
Formally notify the seller of your claim as soon as possible.
You can demand the repair, a price reduction (quanti minoris action) or the termination of the sale (redhibitory action), plus damages if there was bad faith.

The best defence is prevention: a pre-purchase review and warranty clauses in the contract greatly reduce the risk.

Frequently asked questions

We answer your questions

What deadline do I have to claim hidden defects?

The Civil Code sets a short period (six months for the warranty action), although depending on the case other routes with different deadlines may apply. It is advisable to act as soon as the defect is detected.

Is aluminosis a hidden defect?

Yes, if it was not detectable during the viewing and affects habitability or safety. It is one of the most claimed structural defects in older buildings.

Discovered a defect after buying?

We analyse your case and claim from the seller the repair, a price reduction or the termination.

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