Pouring a slab on top of a basement

[Dr Benz]

Hello
We are going to pour a slab on most of the foundation in the existing house. But we also have about 12 square meters of basement where the boiler is located. Can you pour a floor over the part that is above the basement? And how do you handle the insulation there? Otherwise, I think the underfloor heating will go down into the basement unnecessarily. The alternative is to build up over the basement section as it looks today and insulate as it should be, etc.
But I think it might be better to have a homogeneous slab everywhere IF it were possible.

I read somewhere about some kind of sheet metal that you can pour on, but there was probably no insulation, so how do you handle the underside?

 

[Snickarkirre]

Hey! Sure, it's going just fine. It's called vault casting. Google "valvform" to see what it looks like roughly. You'll come across a lot of peri and dokaform, etc., but it's possible to do it with regular planks instead of something like dokabalk (those yellow beams). However, it's an advantage to use real props instead of studs because it's more difficult to dismantle the form and there's more work to build it. There's quite a bit of work with props, planks, and plywood.

But isn't it warm in the boiler room? Not sure if the insulation is necessary there. Those plates you're thinking of are called "bärplåt," and it might be less work with them compared to vault forms. Otherwise, if you want to insulate the slab, you'll need to set up a suspended ceiling and insulate. You can either use regular wooden studs or use z-profiles for that. And then insulate between the studs.

 

[Dr Benz]

Hey! Sure, it's going perfectly fine. It's called casting a vault. Google vault form, and you'll see roughly what it looks like. You'll come across lots of Peri and Doka forms, etc., but you can do it with regular planks instead of something like Doka beams (the yellow beams). But it's an advantage to use proper props and not studs because it makes it harder to dismantle the form plus more work to build it. There's quite a bit of work with props, planks, and plywood.

But isn't it warm in the boiler room? Not sure if insulation is necessary there. Those sheets you're thinking of are called bearing plates, and I imagine they involve less work than vault form. Otherwise, if you want to insulate the slab, you'll need to frame up a ceiling and insulate. You can either use regular wooden studs or Z-profiles for framing, and then insulate between the studs.

Hi. Thanks for the info. It was Plannja Combideck 45 that I had seen somewhere and had in mind. When you pour on it, it should become self-supporting. But you can just adjust the thickness, I think. So that could be an idea.

When it comes to insulation, I'm not sure if it's needed or not. There's a gas boiler now that will be used until it's worn out (10 years old), but then it will be air-water. It might not matter if there's a little heat in the so-called basement even if it's not used for anything specific. The walls are thick, and besides, it's only 12 sqm, so that "loss" might be manageable. I don't mind if the temperature is decent down there, but I don't want to heat the place for nothing.

 

[Snickarkirre]

Okay, as I said, it's probably easier than shaping it, so if it works with that, go for it

You can insulate even if you use combideck. You just need to set up a framework for a ceiling and then insulate between the beams. It might be a bit cumbersome to insulate in the corrugation, but you might be able to cut strips and press them into the corrugation?

 

[Dr Benz]

I think that will be best. I just need to check how long it is. It would be good if it is under 2.4m. But otherwise, I guess I will have to put a beam in the middle.
Thanks for the info.