How far should you trust a builder's 10-year guarantee?

For any project started after July 1 this year the builder and other trades involved in the work should have supplied details of their 10-year insurance and this should meet new minimum standards.

The garantie décennale is taken out by the builder and specifies the scale of the work to be done (including techniques used) and the scope of the cover, the price and time frame of the work being covered and whether joint trades are included. It also gives full contact details for both builder and insurance company.

Details of the information that must be included on the warranty are available on the national housing website www.anil.org which also specifies that insurers are not allowed to insert clauses that reduce the specified cover.

The warranty must be provided along with any quote for work to be done and is essential to reassure the client that the cover is in place before work starts.

It gives the client a written guarantee that the work will be done to standard and that they will have the full use of any construction – house, conservatory, pool, extension or tennis court – for 10 years after completion and that any problems will be resolved.

The cover is also transferable and must be included with sale deeds if the property is sold within the 10-year time-scale.

The assurance décennale is the final part of three guarantees over different time frames that the builder must offer:

• the guarantee of parfait achèvement says that work will be done to standard and that any imperfections or problems will be rectified quickly once notified (by registered letter, if necessary) in the first year after completion

• the garantie biennale says that in the first two years after completion the builder will repair or replace any item not functioning properly (such as a pool pump or a central heating boiler)

• finally, the garantie décennale gives the assurance that the work and linked work will be fully functioning for 10 years. The attestation of insurance is supplied to the new owner if the property is sold within 10 years.

To avoid problems, clients should take out their own assurance dommages- ouvrage that covers work on two levels: firstly, to give cover if the work causes other, unexpected, problems such as a wall cracking in a neighbouring property, but also to give a back-up 10-year cover that is paid for by the client and is in their favour.

Building work can have unintended consequences such as blocking a drain or weakening a support wall and the assurance dommages-ouvrage will get repairs done quickly (within three months) without blame. Secondly, it covers any failings by the builder without waiting for a claim to be processed through their garantie décennale insurance or, worse, for any contested claim to go to court.

Like the builder’s garantie décennale it must be taken out before work starts and gives cover for 10 years after the work has been completed.

The price varies on the value of the work being done and averages 2% of the total.

The assurance dommages-ouvrage may impose a significant extra cost that is paid in one sum, and for a house-holder doing work on their own property or that of any member of their family, there is no penalty for not having it in place.

However, it may mean delays in getting repairs done and, in the case of the property being sold within 10 years, leaves the former owner liable for potential costs incurred by the new owner.