Kitchen Floor - Insulation and UFH

[sammybrush]

Morning,

I am in the process of extending my kitchen into an old wash room and external toilet. Original floors have been dug up and filled with hardcore, compacted and levelled off with sand. I have added a layer of DPM and then added a 100mm slab of concrete.

I have got another 150mm till I am at the correct level of my dining room.

On top of the slab, my thinking is to add insulation, underfloor heating, plywood and then tile on top of the ply.

~ Insulation is going to be 100mm PIR boards Celotex/Kingspan
~ Underfloor heating is, 16mm Polypipe 'Overlay', which is an insulated panel with the pipes laid in the insulation
~ Ply is added at 6mm thick on top of the UFH
~ Tiles to be on top of the ply, i have assumed a depth of 25mm for the tile and adhesive

Total 147mm

Looking on the Polypipe website http://www.polypipe.com/polypipe/site/overlay-home it states that

"Tiles can be laid directly on to the Overlay™ panels or a 6mm plywood lining can be fitted prior to tiling. When tiling directly over Overlay™ panels, use a sealant with flexible adhesive and grout"

So I will be getting my tiler to use a flexible adhesive but i am a wondering if it is acceptable to have the tiles situated on top of two layers of effectively floating polystyrene boards. Or do i have have to make sure that the cutting of the boards is cock on, so that no float on the polystyrene is present? Or can the insulation be 'fixed' to the slab to stop any movement in the plane of the floor?

Or am i completely wrong with my insulation on top of my slab? I just don't see the point of using my UFH to heat up my slab.

The UFH system has been recommend to me by my plumber, as it is supposed to be more efficient and faster at heating up.

Also i will need to put a channel in the floor to account for the gas and water needed in the kitchen. Would people just use the generic 'U' shape ducting, but again i was wondering how i would fix the ducting to the insulation?

Sorry for all the questions

Cheers

 

[mointainwalker]

I just don't see the point of using my UFH to heat up my slab.

A lot of people see that as an advantage of UFH. Slow input, slow even release. It could be though that since this is for a kitchen, probably used less than a living-room that yours is a better idea.

I don;t think it likely that it will be more effective though, especially as the ply is an insulating layer that you are introducing.

Did you consider putting down a 60 mm screed on top of 60 mm of Celotex and embedding the pipe in the screed ? If so, what were the reasons for rejecting it ?

 

[tictic]

you should have laid the 150mm insulation boards,FIRST ....celotex/kingspan..

then put your wet ufh down ...

then your screed..then when cured..
commision the wet ufh to mfr guidelines/instructions..i.e.turn on and raise X amount a day...so you dont thermal shock the screed...then you will bring the temp down gradually over a period of time..again so you dont thermal shock the screed..

then prime the screed..again primer depends on type off screed..either use an acrylic or epxoy primer..

then a uncoupling membrane..ditra etc..again mfr inst.

then flexy tile adhesive..

tiles..

seal tiles if needed..

grout..

wash an polish..

seal tiles if needed..

then a BEER...

what you propose do to do is a NO..NO..

that 6mm ply will fail and your tiles will BLOW off that floor..

 

[Deluks]

Where you are at the moment I would second MW's suggestion, up it to 80mm kspan and 60mm screed, with the pipes embedded, this will only give you about 10mm-ish extra for the tiles, but if the screed is totally level then you could get away with it.

All that ply and custom insulation boards will cost a fair bit compared to doing it the easier way as above. The pipes should be clipped to the insulation or fixed to some wire mesh to hold the shape.

 

[sammybrush]

Thanks for the responses.

Deluks ~ At the moment nothing has been fixed apart from the concrete slab and that i have 150mm left to fit everything in, to be level.

mointainwalker ~ When I initially looked into the UFH and never installed it before, I was open to all methods of construction and I was advised through my plumber that this would be the best option for what I wanted.

tictic ~ I certainly will be having a beer after all this is done. So your advise is to forget my method completely and go for a conventional embedded screed method?

Looking at the Polypipe solid floor method they recommend "The overall quality and thickness of a sand and cement screed should meet the requirements of BS8204-1 which stipulates that in domestic or light commercial applications a minimum thickness of 65mm should be used."

So realistically I should have
50 - 80 mm Insulation - depending on if it meets regs
65 mm of screed with embedder UFH
Primer Uncoupling membrane
tiles and adhesive

Kitchen is roughly 15m2

Cheers

 

[mointainwalker]

I do not understand what purpose the decoupling membrane (expensive product ) is serving here. I'm a DIYer who fitted his own UFH with tiles (after a lot of research)

"..I was advised through my plumber that this would be the best option for what I wanted. "

Hmmm. I may be cynical , but possibly either he didn't want to get into sub-contracting/laying a screed or saw the Polypipe package as easier/bigger invoice value or it was the only way he knew to do it .

 

[Deluks]

I do not understand what purpose the decoupling membrane (expensive product ) is serving here. I'm a DIYer who fitted his own UFH with tiles (after a lot of research)

Might it be to enable easier removal of the tiles without damaging pipework/screed for any future change of floorcovering???

 

[Deluks]

So realistically I should have
50 - 80 mm Insulation - depending on if it meets regs

I think 80-90 or even 100 might be required to meet regs. You'll have to make do with what you've got, don't skimp on the screed though, Personally I'd split the diff, 70-70, get it as flat as poss so you can tile the floor with a wall trowel (smaller ridges)

If building control are involved, tell them you ballsed up and your not digging all that concrete out again and it'll have to do. But be genuinely sincere and not rude.

 

[mointainwalker]

Might it be to enable easier removal of the tiles without damaging pipework/screed for any future change of floorcovering???

I really don't think so . They sell it as giving flexibility to the tiled surface but you are already paying for an expensive ( although much cheaper than this membrane ) flexible glue for that.

 

[tictic]

Might it be to enable easier removal of the tiles without damaging pipework/screed for any future change of floorcovering???

I really don't think so . They sell it as giving flexibility to the tiled surface but you are already paying for an expensive ( although much cheaper than this membrane ) flexible glue for that.

flexible adhesive will only take so much movement/flex from a subfloor.
screeded or wooden.

for a wet ufh system on a screeded subfloor you will have stress/cracking from it when it is curing,so to stop this transfering to the tiles escpeically stone tiles.you will have a failure..i.e grout cracking first,then the tiles tenting/bowing/popping..i have seen a lot off these type of failures..maybe just lack off preperation on the tile fixers part....

but by using a uncoupling membrane such as ditra etc, will elimanate this,espeically with a stone tile...and most or all tile mfr will recommend this method with wet ufh...

anyway to the op..
why dont you go for a 40mm screed (gypsum/anhydrite screed) most house biulders use these now as its a quicker drying time..40mm so 40 days or there abouts(depends on condtions etc..)..ontop off 100mm kingspan/celotex..check with BC first,..but you should be ok..

but when tiling onto this type off screed you will have to do a little more preperation..

removing any lataince from the top off it..give it a sand down..
primer..depedant on addy mfr an acrylic or epoxy primer..
then...
beer..

 

[tictic]

Might it be to enable easier removal of the tiles without damaging pipework/screed for any future change of floorcovering???

I really don't think so . They sell it as giving flexibility to the tiled surface but you are already paying for an expensive ( although much cheaper than this membrane ) flexible glue for that.

shower an beer there..

even when laying wooden flooring over a wet ufh a lot off mfr will re:a uncoupling membrane..

 

[mointainwalker]

for a wet ufh system on a screeded subfloor you will have stress/cracking from it when it is curing

But you are not going to tile it before it has cured, are you ?

and most or all tile mfr will recommend this method with wet ufh...

Can you give some links ? I tried, but don't know who big tile manufacturers are.

 

[meadowhog]

~ Tiles to be on top of the ply, i have assumed a depth of 25mm for the tile and adhesive

Thats a bit thick????