How to dig down my hall for underfloor heating

[Lamentable]

I need to dig down the solid floor of my 1930s property to install under floor heating.

I need to do this to get the heights level across the various rooms - I cannot get a "lay on top" system to work despite best efforts.

The system will look like this - exact model not shown but it is the prefabricated insulated boards with pre-routed pipe runs.

I estimate I need to take the floor down around 30mm to get levels correct but propose taking it down more in order to build it back up level.

My questions - and please note I know very little about building and ground work so I appreciate any advice given:

1. What tool used to break up the concrete - a Hilti ?

2. How much deeper to go in order to get a level surface to put the system on top of?

3. Do I need to put down a damp course?

4. What shall I use to level off the dug out surface?

5. Having never used a cement mixer, is there some sort of compound I can I mix in a bucket to level the surface?

6. The area is around 9 meters square - roughly how long would it take to dig out?

Thank you in advance for any help received!

 

[ree]

OP,
A few pics of the hall would help - show the front door threshold?
Why not read "Similar threads" below - and their "Similar threads"?

 

[endecotp]

Is there insulation under the concrete? Putting UFH on top of an uninsulated concrete floor is a bad idea.

 

[noseall]

I need to dig down the solid floor of my 1930s property to install under floor heating.

I need to do this to get the heights level across the various rooms - I cannot get a "lay on top" system to work despite best efforts.

The system will look like this - exact model not shown but it is the prefabricated insulated boards with pre-routed pipe runs.


View attachment 380761

I estimate I need to take the floor down around 30mm to get levels correct but propose taking it down more in order to build it back up level.

My questions - and please note I know very little about building and ground work so I appreciate any advice given:

1. What tool used to break up the concrete - a Hilti ?

2. How much deeper to go in order to get a level surface to put the system on top of?

3. Do I need to put down a damp course?

4. What shall I use to level off the dug out surface?

5. Having never used a cement mixer, is there some sort of compound I can I mix in a bucket to level the surface?

6. The area is around 9 meters square - roughly how long would it take to dig out?

Thank you in advance for any help received!

You should look at what the make-up of the floor is. You might strike lucky and have a concrete sub-base along with a floor screed, affording you the opportunity to break up the screed and lay your UFH. However, those panels look like they'll need a fair bit of cover, to prevent delamination. What is the recommended minimum cover?

If you have solid concrete floors then a big dig (with machine/breaker) is inevitable and may afford you the opportunity to insulate prior to fitting the UFH.

 

[Lamentable]

I'm not able to provide a picture of the hall at present but hopefully the following plan will help.

The area marked out in red is a solid floor, as is the garage but that is slightly lower down (1 course of bricks).

The area marked in blue is the proposed area to lower.

All other floors are suspended.

The mark up of the floor at present is wooden blocks on a bitumen base, underneath that is concrete.

The front door threshold is currently around 15-20mm above the current wooden blocks.

The system I am looking at has 18mm ceramic "planks" that go above the pre-formed sheets shown above that the pipe sit in, and then the final floor covering on top which will be ceramic tile.

One reason for choosing this system with the ceramic sub floor is that if I have any difference in floor heights between the rooms (likely) I can put a few mm of liquid screed on top of the lower floor to get them level, or potentially loose it in the top ceramic tile adhesive.

I can dig down further and put in more insulation but need to understand the make up of the floor after I have dug down. And, if there is an easy way for me to level that surface with minimal building knowledge before putting something on top.

If I dig down further I could have something like (bottom to top):

Sand
Damp course
Cement, or some sort of compound?
Solid PIR board (Kingspan or equivalent).
The pre-formed UFH sheets
The 18mm ceramic floor planks that are part of the system.
Final floor covering (ceramic tiles).

Does that sound reasonable ?

 

[Ivor Windybottom]

Does that sound reasonable ?

Unless you're planning on digging out the floor in its entirety and replacing with a ground-up brand new insulated slab then no. You'll get huge heat losses into the ground.

Salesmen will tell you otherwise, but retrofitting underfloor heating is usually a terrible idea.

Radiators are what you need.

 

[Lamentable]

I was planning to put in 100mm if kingspan.
Concrete would absorb heat and radiate that outwards, where as kingspan would ensure it moves upwards in the right direction.

 

[Ivor Windybottom]

Oh fine then. But bear in mind that you will never get back the cost of insulating a concrete floor in reduced heating costs.

But if you really insist on having underfloor heating in an old house then it's the only sensible way of doing it.