New construction: Doing heating and plumbing yourself?

Hello everyone,

we are planning a new building and are considering not having the heating and sanitary installations done through the developer.

The background is that we could get heating (underfloor heating), ventilation system, air heat pump, and sanitary products relatively cheaply, but we would then have to take care of finding a craftsman to install them. We cannot do this ourselves.

On the one hand, we would certainly save money; on the other hand, I have concerns for the following reasons:

- I am not exactly sure when the heating/sanitary package will be scheduled, meaning I need to be able to order materials and craftsmen flexibly. Is that possible?
- Who assumes liability? Not the developer.
- What happens if I cause delays?

Does anyone have experience with this topic and can help?

Many thanks and best regards!

Does anyone have experience with this?

The background is that we could get heating (underfloor heating), ventilation system, air source heat pump, and sanitary product relatively cheap,

Can't everyone do that?

we would then have to take care of a craftsman to install this. We can't do it ourselves.

Then find a craftsman who does not install his own material, because

- Who takes liability? Not the developer.

that must be taken by the craftsman. But I would charge a lot for something like that. Or just not do it.

I don't know exactly when the heating/sanitary package is due, meaning I have to be able to order material and craftsmen flexibly. Possible?

Possible yes. But which craftsman can say that he a) installs foreign goods and b) is just waiting for your call so he can work next week. If you can store material, the problem would at least be solved. I only see craftsmen from classifieds or similar portals who "just come by" and install your goods. But in case of doubt, they are no longer reachable if problems arise.

- what happens if I am delayed?

Bad luck and house construction stalls. In the worst case for a really long time, because the work planned by the builder for you cannot be done. And afterwards, other construction sites are dealt with until there is time again for your house construction. This will be overall difficult. It would be good if you could do things yourselves (laying underfloor heating + subsequent acceptance by a craftsman is already almost common). You can also install sanitary products on the wall even with two left hands.

Standard question: main contractor (GU) or developer? I can already imagine that it might be difficult for a developer to remove services because of their warranty, but it’s worth asking. Regardless of whether it’s a main contractor or a developer, the first question in the negotiation is how much of the agreed total price will be discounted to you, and possibly unexpected negative answers.

What does "relatively cheap" mean? At the same purchase price as the craftsman? Or even cheaper? I don’t want to ask why, just the question of the order of magnitude. So first determine the maximum possible saving.

That means the craftsman waives the part of his margin that he makes on the markup on materials, assumes warranty for materials for which he himself has no warranty from the supplier side, and has you as the client/contact person while the rest of the trades are managed by the main contractor? I would initially say the construction market hasn’t cooled down so much yet that you’d quickly find interested parties there, but that’s just a guess. Trying it out makes you wiser—also whether in negotiations for the lost material markup only higher prices for installation will be charged, which would reduce the calculated maximum.

So overall: it can be checked, but if in doubt better to give up the check as fruitless sooner rather than later and keep the trades included in the scope of services.

No craftsman will do it, at most illegally without any warranty. Who knows what kind of refurbished C-grade goods you'll get, even if you believe everything is new.

If you fall behind schedule, not only can the construction come to a halt, but the construction company might also hold you liable, your fixed price falls through, etc.

And all damages and defects that occur later will be blamed on your "own work".

Such stories are only worth it imo if you can then install them yourself (and are a professional), otherwise: nothing gained but expenses and trouble.

Such stories are only worthwhile IMO if you can install it yourself (and are a professional)

Although these are still relatively simple things. Installing underfloor heating is purely hard work – with continuous installation, there are only the connections to the manifold where defects can be quickly seen. You do the pressure testing yourself as well. The pump for that costs €20 to rent. And mounting plumbing on the wall is, besides painting, one of the easiest tasks. However, you are not allowed to lay water lines yourself (even if it is idiot-proof with a press tool).