How should I think about the basement floor?

[Selleus]

Hello!

We have a house from 1924 with a basement. In the 70s, the house was expanded, and the basement was also expanded with a recreation room. We have now torn down walls and floors and discovered that there is about 10 cm of sand under the floor. From what we understand, this is called a “floating floor”? Under the sand, there is likely an uninsulated concrete slab.

Right now, we are in the process of removing all the sand to get down to the slab.

We want to install new flooring and make the area a functional part of the living space, but we are getting different advice on how to proceed. As I understand it, it requires breaking up and casting a new slab with insulation underneath if you want to install water-based underfloor heating – but that seems to be the most expensive solution.

On the basement level, we also have a bathroom that we want to renovate. We suspect some moisture there, so the plan is to tear everything down to the foundation before building it up again.

We are considering installing underfloor heating there as well – is it possible to do that without breaking up the slab? We can also consider electric heating if there is a difference in preparation or construction.

Therefore, we wonder:

– What is the best approach if you want modern and comfortable flooring, preferably with underfloor heating?

– Do we need to break up the entire slab, or are there solutions where you can build on top of the existing one?

– Are there risks with keeping the current construction, such as moisture or settling?

– Is there any “middle way” that is sensible in terms of both function and cost?

– And if we instead choose to install regular wall-mounted radiators – how cold does the floor feel in such a basement?

– Can you install underfloor heating (water or electric) in a basement bathroom without breaking up the floor? What is required?

We gratefully accept all thoughts, experiences, and tips – gladly also pictures if anyone has any!

 

[Belastar]

Hello!


We have a house from 1924 with a basement. In the 70s, the house was expanded, and the basement was also expanded with a recreation room. We have now torn down walls and floors and discovered that there is about 10 cm of sand under the floor. From what we understand, this is called a "floating floor"? Under the sand is likely an uninsulated concrete slab.





Right now we are removing all the sand to get down to the slab.





We want to install a new floor and make the area a functional part of the living space, but we're getting different advice on how to proceed. As I understand it, you need to break up and cast a new slab with insulation underneath if you want to install water-based underfloor heating — but that seems to be the most expensive solution.





On the basement level, we also have a bathroom that we want to renovate. We suspect some moisture there, so the plan is to tear everything down to the foundation before rebuilding it.


We are considering installing underfloor heating there as well — is it possible without breaking up the slab? We could also consider electric heating if there are differences in preparation or construction.





Therefore, we wonder:


– What is the best approach if you want a modern and comfortable floor, preferably with underfloor heating?


– Do we need to break up the entire slab, or are there solutions where you can build on top of the existing one?


– Are there risks with keeping the current construction, such as moisture or settling?


– Is there any "middle way" that makes sense both functionally and cost-wise?


– And if we instead choose to install regular radiators on the wall, how cold does the floor feel in such a basement?


– Can you install underfloor heating (water or electric) in a basement bathroom without breaking up? What is required?





Gratefully accepting all thoughts, experiences, and tips — preferably with pictures if anyone has any!

What's the point of complicating things with underfloor heating everywhere??

 

[Selleus]

What's the point of complicating things with underfloor heating everywhere??

I'm open to suggestions. Mostly thinking that it's an efficient heating system and your feet won't get cold if you have tiles.

 

[Belastar]

I am open to suggestions. Mostly thinking it is an efficient heating system and you won't get cold feet if you have tiles.

I would rather have radiators instead of tearing up an entire floor with a lot of work. Much easier with a pair of slippers.

 

[Selleus]

I would have preferred radiators instead of tearing up an entire floor with a lot of work. Much easier with a pair of slippers.

Okay. Thanks for the input. How would you have done it then? Lay tile directly on the base slab?

 

[Belastar]

Alright. Thanks for the input. What would you have done then? Put tiles directly on the foundation slab?

Yes .

 

[Selleus]

And it's not a problem from a moisture perspective?

 

[Oldboy]

No.

However, depending on whether and how much moisture migrates through the concrete slab, furniture on legs, not skirting boards, and moisture-permeable carpets are suitable. This way any moisture can be ventilated away by the indoor air/house's ventilation system.

What type of flooring was there before, i.e. the one you removed? If it was a dense plastic mat and no moisture problems were detected, then the moisture migration should be minimal and there should not be any significant issues.

Moisture migration primarily depends on the type of soil and drainage. The soil type doesn’t change, but the drainage’s function can change over time, so if the house is situated on naturally moist ground, the drainage might be crucial for moisture. If the house is on naturally dry and well-drained ground, the drainage plays less or no role at all.

 

[Selleus]

There was a wall-to-wall carpet glued on something like masonite. Under the masonite, there was a plastic film, followed by 10 cm of packed sand.

 

[Selleus]

You can see in the sand that there is a bit of moisture in certain places.

 

[JMKL]

Hello!


We have a house from 1924 with a basement. In the 70s, the house was extended, and the basement was also expanded with a recreational room. We have now torn down walls and floors and discovered that there is about 10 cm of sand under the floor. From what we understand, this is called a "floating floor"? Likely, there is an uninsulated concrete slab under the sand.


We are currently removing all the sand to get down to the slab.


We want to install a new floor and make the area a functional part of the living space, but we're getting different advice on how to proceed. As I understand it, if you want to install water-based underfloor heating, you have to jackhammer up and cast a new slab with insulation underneath—but that seems to be the most expensive solution.


On the basement floor, we also have a bathroom that we want to renovate. We suspect some moisture there, so the plan is to tear everything down to the foundation before rebuilding it.


We're considering installing underfloor heating there as well—is it possible to do so without jackhammering up the slab? We can also consider electric heating if it differs in preparation or construction.


Therefore, we wonder:


– What is the best way forward if you want a modern and comfortable floor, preferably with underfloor heating?


– Do we need to jackhammer the entire slab, or are there solutions where you can build on top of the existing one?


– Are there risks in keeping the current construction, such as moisture or settling?


– Is there a "middle ground" that is reasonable in terms of both function and cost?


– And if we instead choose to install regular radiators on the wall, how cold will the floor feel in such a basement?


– Can you install underfloor heating (water or electric) in a basement bathroom without jackhammering? What is required?


We gratefully welcome all thoughts, experiences, and tips—preferably even pictures if anyone has any!

We are also new homeowners, torn down the recreational room that had the same construction as yours. We will probably lay tiles or a leveling floor. If you install underfloor heating without insulating under the slab, there is a risk of reverse moisture migration.

 

[cpalm]

Here you have an awesome guide with a lot of info about the options:
https://www.husgrunder.com/renovera-husgrund/grava-ur-kallaren-och-isolera/

I assume the ceiling height is ample since the old floor added 10 cm? Otherwise, it's often the limiting factor.

 

[Selleus]

We are also new homeowners, torn down the rec room which had the same construction as yours. We will probably lay clinker tiles, alternatively a leveling floor. If you install underfloor heating without insulating under the slab, there is a risk of reverse moisture migration.

Will you lay the clinker tiles directly on the base slab or will you put something else first?

 

[Selleus]

Here you have an awesome guide with a lot of info about the options:
[link]

I assume the ceiling height is generous since the old floor was 10 cm? That's often the limiting factor otherwise.

The ceiling height is not good. I can reach the ceiling with my palm 😑. Will measure later.

 

[Selleus]

The ceiling height is not good. I can reach the ceiling with my palm 😑. Will measure later

Here's an awesome guide with tons of info about the options:
[link]

I assume the ceiling height is generous since the old floor was built up 10 cm? Otherwise, it's often the limiting factor.

I would say the ceiling height is about 220 cm