Floor Insulation

[Homer92]

I am getting to stage to lay my floor insulation.

225mm floor depth - 150mm PIR Boards (2 layers of 50mm and 100mm) and 75mm sand/cement screed. UFH throughout ground floor.

 

I have a few questions before I start - I was thinking of laying the 50mm board first so they will butt up tight to the plumbers lagged copper pipes and put the 100mm board over the top. It will save tracking the pipe lengths out of the 100mm thk board for plumber's pipes. Is this best way to do this?

 

What is the DPC detail along the blockwork? Does it return up the blockwork and the insulation just butts up tight to it?

 

For the 25mm thick edge perimeter insulation is it ok for it to sit on top of the first 50mm board or should it go down to the subfloor?

 

Is a layer of polythene required on the subfloor under the insulation and if so what  is it's detail when it reaches the blockwork?

 

Sorry for all the questions!

 

[DevilDamo]

Plumbers pipes as in the underfloor heating? If so, the pipework would normally be positioned within the screed and therefore above the insulation.

 

DPM runs on top of the concrete/beam and block floor, under the block skin, lapped up the external face of the internal skin and coursed. DPC physically laps with the DPM along with cavity trays if required.

 

The perimeter strip can go down to the floor or sit on an insulation board.

 

Do you not have an architect/designer which explains and details these connections?

[wozza]

We laid a normal (thick DPM) on the sub floor, lapped up the walls with all joints overlapped and taped, blobs of mastic used to stick it to the walls.

We fitted our 25mm PIR perimeter insulation next (slightly higher than FFL) We then fitted our 120mm PIR insulation, we taped the boards together but I don't think it necessary.

We then laid a thin DPM over the PIR (and up the walls) again with overlapped and taped joints.

The UFH pipes were then fitted and then screed poured.

Edited November 25, 2020 by wozza
I cor spell

[Homer92]

3 hours ago, DevilDamo said:

Plumbers pipes as in the underfloor heating? If so, the pipework would normally be positioned within the screed and therefore above the insulation.

 

DPM runs on top of the concrete/beam and block floor, under the block skin, lapped up the external face of the internal skin and coursed. DPC physically laps with the DPM along with cavity trays if required.

 

The perimeter strip can go down to the floor or sit on an insulation board.

 

Do you not have an architect/designer which explains and details these connections?

Great, thanks for replies.

 

Plumbers pipes as in his domestic copper pipes (hot/cold from taps, toilets etc).  How have people insulated around these with PIR board?

[Jason L]

17 minutes ago, Homer92 said:

Great, thanks for replies.

 

Plumbers pipes as in his domestic copper pipes (hot/cold from taps, toilets etc).  How have people insulated around these with PIR board?

That sounds like a poor place to put them to me, like you say it’s difficult to insulate around them so you will have a cold bridge there. And then what if you get a leak or they burst? 

[Homer92]

9 minutes ago, Jason L said:

That sounds like a poor place to put them to me, like you say it’s difficult to insulate around them so you will have a cold bridge there. And then what if you get a leak or they burst? 

where is the alternative to locate them?

[PeterW]

30 minutes ago, Homer92 said:

Great, thanks for replies.

 

Plumbers pipes as in his domestic copper pipes (hot/cold from taps, toilets etc).  How have people insulated around these with PIR board?

If they are run in a floor then use Hep2O conduit pipe and foam it into grooves cut into the foam. No joins in the floor and easy to run. 

[m0deller]

2 minutes ago, Homer92 said:

where is the alternative to locate them?

Above (ceiling void) and drop down. 

[Jason L]

7 minutes ago, PeterW said:

If they are run in a floor then use Hep2O conduit pipe and foam it into grooves cut into the foam. No joins in the floor and easy to run. 

That sounds like a plan ?

[Homer92]

6 minutes ago, m0deller said:

Above (ceiling void) and drop down. 

 

Is it uncommon to run these along the subfloor under the insulation?  

Plumber never discussed alternatives, they have started putting all copper domestic pipes on subfloor.

 

 

 

 

 

[PeterW]

20 minutes ago, Homer92 said:

 

Is it uncommon to run these along the subfloor under the insulation?  

Plumber never discussed alternatives, they have started putting all copper domestic pipes on subfloor.

I wouldn’t be burying copper until it has been pressure tested and also ensure it is not in contact with any concrete. Have you specified copper or have they chosen it..?

[Homer92]

9 minutes ago, PeterW said:

I wouldn’t be burying copper until it has been pressure tested and also ensure it is not in contact with any concrete. Have you specified copper or have they chosen it..?

 

They are pressure testing it prior to any insulation is laid. They chose copper, they have used a plastic conduit (I assume Hep20) for rads upstairs. 

I will ask why they chose copper but I just assumed it was more heavy duty for floor loading above it.

 

I'm just struggling to see how they could have been positioned in voids above and drop down, for eg. kitchen sink is under a window with a vaulted ceiling ? surely it has to come across the floor.

[Onoff]

Slightly off topic but I have a relative who's idea for UFH was 1" Celotex, a load of soldered up 15mm copper pipe (lots and lots of elbows). Protection consisted of wrapping, as best as, the pipes in bits of DPM and rubble bags. Dry screed over the top. All run off the normal radiator circuit. Been running for years with seemingly no issue. I imagine the heat losses downward must help to prevent over heating?

 

?

[James94]

Does it make any difference to the u value if you choose to multiple thicknesses of pir to achieve required depth or any advantages, would it be cheaper? Got this stage still to think about at a later date, would love to see some pics of flooring stages and methods.

Regards. James

[farm boy]

I am in a similar position to Homer92 , in the new year I am planning to install 2 x 75mm celotex then 85 screed to get to the right level. I figure the 75mm will be easier to handle and cut than one 150mm layer. I intend to put the layers of insulation in an overlapping pattern. Putting the hot and cold plumbing pipes in a groove in the insulation sounds good but does not allow future access or adaptation. We had a builder do an extension on our existing house about five years ago and he made a conduit out of timber on the sub floor DPM then a thiner depth of the insulation and screed over top. Contains a waste pipe and hot and cold feeds with access either ends under kitchen units and at stack. I don't intend to fit a perimeter edge as my full fill cavity goes right down to the concrete sub floor to overlap. I cannot see multiple layers make a difference it’s the total depth that counts. Not intended to tape my DPM and DPC together but just use a generous overlap, over 200mm on the perrimeter edge.Everyone has a different situation on here. Looking to buy my insulation before New Year in case of price increase.

[PeterW]

58 minutes ago, farm boy said:

I don't intend to fit a perimeter edge as my full fill cavity goes right down to the concrete sub floor to overlap

That insulation is there to accommodate expansion not just for thermal purposes. You need to include it. 

[wozza]

1 hour ago, farm boy said:

I don't intend to fit a perimeter edge as my full fill cavity goes right down to the concrete sub floor to overlap. 

 

Would the wall draw the heat out from the slab?  

[farm boy]

On 26/11/2020 at 20:38, PeterW said:

That insulation is there to accommodate expansion not just for thermal purposes. You need to include it. 

Does that mean  I only need it at the screed edge 

 

[PeterW]

29 minutes ago, farm boy said:

Does that mean  I only need it at the screed edge 

 

 

You need it where the screed hits a solid wall so that could include any internal load bearing walls

[farm boy]

29 minutes ago, farm boy said:

Does that mean  I only need it at the screed edge 

 

I ve just found the labc ufh guide online. I now understand what you mean. Thanks.

I ve had a few prices from ufh online sellers and they all included a roll of perimeter insulation.

[Onoff]

I have an expansion strip and perimeter insulation.

 

 

[wozza]

2 hours ago, Onoff said:

I have an expansion strip and perimeter insulation.

 

 

 

Me too

 

[wozza]

3 hours ago, farm boy said:

I ve just found the labc ufh guide online. I now understand what you mean. Thanks.

I ve had a few prices from ufh online sellers and they all included a roll of perimeter insulation.

 

When they say perimeter insulation they most likely mean an expansion strip - its typically about 8mm thick and will not offer much insulation, its there to accommodate expansion.

 

[Onoff]

This is the expansion strip I used. Corrugated cardboard that comes flat and folds into an L shape. Self adhesive. 

 

 

 

 

[farm boy]

Thanks for putting the photos on. I can see you used the pre formed sheet pipe clip system, I notice some people put another layer of polythene over the insulation and then use the clips that spike into the insulation. Not sure which system to go for, I guess it comes down a compromise between the price of materials and ease of fitting. Most of my pipes will be at 100mm spacing so I can see the pre-formed sheet saving a lot of work.