New extension floor level below existing house

[TonyWarrington]

Looking for advice on how to deal with different floor levels between a newly built extension for my son and daughter in law.

They have built an extension of approx 6m x 3m to the rear of their property making it open plan into the living room and kitchen areas by a builder. The problem is that the extension floor is approx 26mm below the existing floor over the entire 18 sq/m area that it covers. The whole ground floor area including the extension is laid to concrete.

While I have not been directly involved with this project or the builder it seems to me that the extension floor should have been brought up to level with the existing building floors. Architect drawings also mention no difference in height!

From what I have heard the builder seems to think that this is a job my son and daughter need to address and is not his concern.

So looking for any advice and suggestions:
1. If they have to take on this work and employ someone to finish leveling what is the recommended way to do this and how costly is it likely to be?

2. Should the builder be brought to task (perhaps holding back final payment until fixed)assuming that the contract and plans show that the flooring should be even between old and new?

3. What would you consider to be right and fair for all concerned?

 

[^woody^]

Floors should run level unless specifically designed otherwise.

Get the builder to rectify at his cost, or withhold payment subject to quotes from others.

A suitable self leveling product would be best.

 

[TonyWarrington]

Thanks ^woody^, "floors should run level" in the architect's plans, and nothing else either was specified or discussed.

I believe the builder underestimated the amount of concrete for the extension which I can imagine is easy to do, but is now trying to shirk his responsibilities unfairly and in the process he may be in danger of being in breach of contract if he is not prepared to rectify at his cost. I really hope that this is not the case

I believe he is getting someone in to quote for the work, and I am hoping that he means to rectify the flooring issue at his cost i.e. my son will pay his contractor and deduct the cost from the final settlement to the builder

 

[TonyWarrington]

Just a quick update the builder did finally decide to do the right thing and employed a specialist to finish the floor level as shown in architects drawing; job took about 2 hours to complete.