External foundation slab contracting – sensible or risky?

Dear forum,

we are facing some decisions regarding our planned prefabricated house project with the company Bien-Zenker.

The local Bien-Zenker provider advertises having the foundation slab built by a local contractor, as this is cheaper than having it done directly by Bien-Zenker. What is your opinion on this, especially considering that this would involve two different trades and Bien-Zenker would only be responsible starting from the foundation slab?

Thank you very much!

The local Bien-Zenker provider advertises having the foundation slab built by a local contractor, as this is cheaper than having Bien-Zenker do it directly. What is your opinion on this, also considering that it then involves two trades and Bien-Zenker would only be responsible from the foundation slab onwards?

Don’t let yourself be talked into splitting the contract "house construction contract" and "foundation slab." The top edge of the basement ceiling or foundation slab is an extremely critical interface. One should not give the supplier any leverage to shift responsibility onto a third party. The trouble—just the delays during disputes about whose fault a poor fit is—is not worth chasing any "savings" here. The salesman kills two birds with one stone: he takes the house manufacturer out of the risk of liability for the work of his subcontractor and receives more commission from the foundation slab provider than if the contract package remains connected as is objectively required.

From a warranty perspective, it is a disadvantage as writes. On the other hand, many houses are built this way - ours too. The foundation work and floor slab were done by BKB Koch and the house by SK Holzbau.

Everyone has to decide for themselves. I would consider it once I have saved a certain amount (around 5k). You will then get the statics for the floor slab and pass them on as they are. For the sewage and ventilation pipes, it probably won't hurt to measure again yourself on the construction site before the slab is poured. Things often go wrong there or measurements are not made very precisely. I wouldn't handle it through the sales representative but would look for a company myself.

How do you see this also against the background that these are then two trades and Bien-Zenker is only responsible from the base plate onwards?

You usually even have a third trade involved: the electrician! You need the grounding of the building and this must be carried out and documented by a specialist. This is all required for the registration of your power connection. Either your base plate builder has a specialist or the electrician who installs your connection is brought on board.