Floor Insulation, UFH, Screed

BMD

Can anyone give me some quick advice on floor insulation with respect to screed and UFH. I am using 150mm of floor insulation but want to know if should these boards be stuck together so as to fill the gaps to stop the screed from flowing between the gaps.

If a polyethene sheet is being used, should this be fitted above or below the UFH pipes (reasoning would suggest below but just want to check)?

Finally are there alternatives to using board insulation for the 25mm up-stand insulation around the perimeter?

peterc14

BMD wrote: »

Can anyone give me some quick advice on floor insulation with respect to screed and UFH. I am using 150mm of floor insulation but want to know if should these boards be stuck together so as to fill the gaps to stop the screed from flowing between the gaps.

If a polyethene sheet is being used, should this be fitted above or below the UFH pipes (reasoning would suggest below but just want to check)?

Finally are there alternatives to using board insulation for the 25mm up-stand insulation around the perimeter?

. Generally just abut the insulation and use tape over the joints.
. Then layer of polythene over insulation prior to fitting of ufh pipes and screed.
. If using a sand/cement screed it is all pretty straight forward. However if using a liquid screed more attention to detail has to paid to ensure that no insulation escapes below the polythene layer and insulation.
. Polythene is generally fitted above insulation but i believe it is good practice to put above and below.
. Not sure about alternatives to the 25mm upstand,

BMD

If the boards are well taped, is there really a need for the sheet of polyethene?

Also, if the walls are dry-lined (38mm insulation) to the slab, does this possibly negate the need to the 25mm up-stand?

peterc14

BMD wrote: »

If the boards are well taped, is there really a need for the sheet of polyethene?

If well taped, then possibly do not need, but most ufh men will put a sheet down as standard practice.

However, as I said if you are using a liquid screed it changes things signigicantly. Sand/Cement screed will not got to far (even on badly taped joints) however a liquid screed will run through every minor crack/gap/break in the tape/membrane.

muffler

BMD wrote: »

If the boards are well taped, is there really a need for the sheet of polyethene?

There is, yes. The cement content of the screed can interact (chemically) with the insulation so you need to keep the 2 warring factions apart

BMD

Thanks Muffler...unfortunately it might be too late for me to get the polyethene sheet in now (UGH pipes are down). Its a sand/cement screed that I am using so I should be OK regarding it running between any potential cracks but just have to hope the cement and insulation don't react!!

Any advice on the drylining and the upstand?

sydthebeat

BMD wrote: »

If the boards are well taped, is there really a need for the sheet of polyethene?

Also, if the walls are dry-lined (38mm insulation) to the slab, does this possibly negate the need to the 25mm up-stand?

no it doesnt, the 25mm is there to prevent a cold bridge between the screed and the block wall. Its a regulation that you must adhere to.

Do not consider bringing the drylining board below the screed level. wet concrete will destroy the board.

as you are using a 37.5 mm drylining board, you can actually afford to install wider perimeter insulation. Id install 50mm and allow the drylining to touch this insulation. The line of insulation will be hidden once you incorporate a skirting board and floor finish.

galwaytt

muffler wrote: »

There is, yes. The cement content of the screed can interact (chemically) with the insulation so you need to keep the 2 warring factions apart

..that depends on the material he's using as floor insulation - he hasn't told us what that is.

castleking1

I have put the dry-lining board tight to sub-floor in a few places. Will I get away with putting perimeter insulation against the board with plastic sheet also. Will this prevent the wet concrete damaging the board.

sydthebeat

castleking1 wrote: »

I have put the dry-lining board tight to sub-floor in a few places. Will I get away with putting perimeter insulation against the board with plastic sheet also. Will this prevent the wet concrete damaging the board.

i wouldnt bet on it.

how do you intend fixing the skirting board?

the best solution to your problem is to cut the base of the CPB's (composite plaster boards) about 50mm above your finished floor level. Go ahead an install your polythene sheeting, UFH and pour screed. Then fix a 50 x 50 batten (thickness depending on thickness of CPB) in the gap between the finish floor level and the CPB. Use this ground to fix the skirting board to, after youve installed your floor finish. Caulk seal the skirting board to the CPB and the floor finish.

bobbuk

Can anyone recommend someone to do the sand and cement floor screed (preferibly someone outragously in-expensive)

BryanF

bobbuk wrote: »

Can anyone recommend someone to do the sand and cement floor screed (preferibly someone outragously in-expensive)

where?

bobbuk

That would help eh....
im based in Navan, so anywhere in the Leinster region I guess.

Cheers

Bob

Hair's Pam

galwaytt wrote: »

muffler wrote: »

There is, yes. The cement content of the screed can interact (chemically) with the insulation so you need to keep the 2 warring factions apart

..that depends on the material he's using as floor insulation - he hasn't told us what that is.

Hi we're currently doing the same regarding underfloor heating n I don't know anything about layer of polythene over insulation. We're laying 100mm Ballytherm Insulation on sat n our plumber will start laying pipes next week. Will the sand cement react to this or is there any need for polythene cover. Thanks in advance for help.