Decoupling Matt

[nod]

I’m busy for the next two weekends tiling the four bathrooms 

My wife helped me with the matting on the last one and decided to do a couple of rooms today 

Nice neat job I’ll have to show the tilers that work for me I can’t remember them sponging  all the joints She’s used 90 m2 yesterday and today Another 110 m2 for her to do next weekend 😁

[ProDave]

200m² of matting?  you have more bathroom area than my entire house.

[nod]

3 minutes ago, ProDave said:

200m² of matting?  you have more bathroom area than my entire house.

Just GF 

In doing the bathrooms myself 

[JackofAll]

What thickness is the mat @nod also what brand, thanks.

[nod]

It’s Dura mat I normally use Ditra But my wife found this at £800 for seven rolls Which is nearly twice what pay for Ditra There a 5 mil build up once fixed 

Edited April 30 by nod

[Canski]

2 minutes ago, nod said:

It’s Dura mat I normally use Ditra But my wife found this at £800 for seven rolls Which is nearly twice what pay for Ditra There a 5 mil build up once fixed 

do you mean half what you pay for ditra ? I used Ardex AF 200 plus to stick my Ditra down. I wasn't very impressed with either the coverge or the efficiency. I presume you use tile adhesive  ?

[jayc89]

3 minutes ago, Canski said:

do you mean half what you pay for ditra ? I used Ardex AF 200 plus to stick my Ditra down. I wasn't very impressed with either the coverge or the efficiency. I presume you use tile adhesive  ?

 

I bought some of that stuff too, and forgot about it, so used the same adhesive as what I used for the tiles on top of the mat. Seems to have worked a treat. 

[nod]

9 hours ago, jayc89 said:

 

I bought some of that stuff too, and forgot about it, so used the same adhesive as what I used for the tiles on top of the mat. Seems to have worked a treat. 

Yes Ditra is nearly -£200 per 30m2 

Ardex is for timber floors 3 mil notched trowel Expensive But bombproof 

My wife stuck this down with flexi tile adhesive 5 mil notched 

Couldn’t wait for me 

I normally pay my tilers a fiver m2 But she’s getting nothing for jumping the gun 😁

[JackofAll]

Sorry for long winded post. So have been told that UF heating would need to be run for a couple of weeks to find out where the cracks will form (if any) in the floor before tiling can commence. We've no power connected and have no idea when it will be. Currently under pressure to get kitchen in as we've postponed it several times due to hold-up's at various stages of the project.

 

Anyhoo, a few different tilers that we've spoken to recommend not covering whole floors with decoupling mat but only cover where cracks are in floor. But am thinking if we covered whole kitchen floor with decoupling mat it wont matter where cracks form(if any) as the membrane stops cracks cracking tiles? and kitchen can be fitted. Anyone forsee any issues?

Edited October 2 by JackofAll

[Pocster]

5 hours ago, JackofAll said:

Sorry for long winded post. So have been told that UF heating would need to be run for a couple of weeks to find out where the cracks will form (if any) in the floor before tiling can commence. We've no power connected and have no idea when it will be. Currently under pressure to get kitchen in as we've postponed it several times due to hold-up's at various stages of the project.

 

Anyhoo, a few different tilers that we've spoken to recommend not covering whole floors with decoupling mat but only cover where cracks are in floor. But am thinking if we covered whole kitchen floor with decoupling mat it wont matter where cracks form(if any) as the membrane stops cracks cracking tiles? and kitchen can be fitted. Anyone forsee any issues?

I felt happier running ufh with no matting just to check and almost deliberately let any cracks appear ( doorways in my case ) . Then I matted the lot .

Cant you setup any short term power ? - borrow from neighbors / generator . Not strictly essential to run ufh with no matting - but I felt happier .

[Andehh]

We have 45sqm of tiles on of Chem floor, used for 12 months.... Touch wood no issues.

[JackofAll]

6 hours ago, Pocster said:

I felt happier running ufh with no matting just to check and almost deliberately let any cracks appear ( doorways in my case ) . Then I matted the lot .

Cant you setup any short term power ? - borrow from neighbors / generator . Not strictly essential to run ufh with no matting - but I felt happier .

left out a vital piece of info, we haven't even installed the ashp yet, probably 5/6 weeks away.

[JackofAll]

3 hours ago, Andehh said:

We have 45sqm of tiles on of Chem floor, used for 12 months.... Touch wood no issues.

Anti crack matting used?

[Andehh]

No, builder was utterly confident without it. Same with our en suites, albeit it a different tiler did our family bathroom and put it in.

 

We had the cemfloor down for a good few months before tiling though.

[Kelvin]

Many ASHP/UFH have a floor drying mode. It ramps up to max temperature over a number of days and then brings the temperature back down again. We then switched it off for 48 hours before we started tiling then left it off for a few weeks after tiling. We also used Ditra mat and expansion joints at every door and across the biggest run of tiles in the open plan area. Screed was Cemfloor. Best practice? Overkill? 

[saveasteading]

22 hours ago, JackofAll said:

but only cover where cracks are in floor

If it has been down long enough (4 weeks say), any cracks should have stopped moving.

I've never used decoupling matting and never had problems. Is it really  a way of tiling early on a  new screed and otherwise unnecessary?

It must also be a heat barrier with UFH.

 

[JackofAll]

8 hours ago, saveasteading said:

If it has been down long enough (4 weeks say), any cracks should have stopped moving.

I've never used decoupling matting and never had problems. Is it really  a way of tiling early on a  new screed and otherwise unnecessary?

It must also be a heat barrier with UFH.

 

The floor is concrete, been poured since August 2023. no cracks to date but have been assured that it will crack when heating is up and running. I guess as the tiles are costly may be foolish not to use matting? the guy suppling the tiles thinks we're mad to use it(matting) even though would be supplying it,go figure! you could well be right re. tiling early.

[Andehh]

Logic being most tile adhesive has a degree of flex, as does grout... As long as the substrate is solid with no movement, any minor minor crackage is likely to be absorbed, or will show in grout (so regrout) or worse worse case... Would pop a tile(!?).. Would it?

 

The physics of a cemfloor type floor moving enough to damage tiles doesn't line up in my mind?

 

 

[Gus Potter]

On 07/04/2024 at 17:40, nod said:

She’s used 90 m2 yesterday and today Another 110 m2 for her to do next weekend

Top comment. One of the builders that I work with came round today and we were talking about not getting our own house finished. His wife has said to him.. if you don't pull your finger out then I'll do it. He said.. my wife is a better trades person than I and bloody handy on the tools! I need to finish it to avoid embaressment! (excuse the spelling)

 

On 07/04/2024 at 17:40, nod said:

I’m busy for the next two weekends tiling the four bathrooms

That's a good photo Nod showing the shrinkage crack adjacent to the stair and what a decoupling matt actually looks like.. it lets Buildhubbers see what can be expected without drama.

 

Bit of tecky stuff for all. Very roughly screeds and concrete slabs that are cement based (even with additives) go through a journey after they are placed. In the first 24 to 48 hours  they undergo what is called plastic shrinkage and this tails off after a bit. But this induces residual stress that does not go away. All the chemicals are interacting and bonding and this causes movement that we call this plastic shirinkage. Next you have drying shrinkage and this is the thing we are interested most in when doing UF and say tiling on top say.

 

On 02/10/2024 at 09:57, JackofAll said:

Sorry for long winded post. So have been told that UF heating would need to be run for a couple of weeks to find out where the cracks will form (if any) in the floor before tiling can commence. We've no power connected and have no idea when it will be. Currently under pressure to get kitchen in as we've postponed it several times due to hold-up's at various stages of the project.

 

Anyhoo, a few different tilers that we've spoken to recommend not covering whole floors with decoupling mat but only cover where cracks are in floor. But am thinking if we covered whole kitchen floor with decoupling mat it wont matter where cracks form(if any) as the membrane stops cracks cracking tiles? and kitchen can be fitted. Anyone forsee any issues?

If it was my own house I would want to heat the slab up to the working temperature in the winter. While at the moment you may not see any cracks the slab could be in tension and a bit of extra heat will cause a sudden opening of a crack.. probably one you can't see from the plastic shrinkage.

 

In my own mind if you just put a matt over the cracks you will just shift the movement elsewhere. Also the matt is quite thick so you'll need to make up the levels which could cost a fair bit on adhesive etc?

 

Can you not just fit the kitchen and install the floor finishes later or do you you have free standing and mobile units?

13 hours ago, saveasteading said:

I've never used decoupling matting and never had problems. Is it really  a way of tiling early on a  new screed and otherwise unnecessary?

It must also be a heat barrier with UFH

I never used to use a matt until I tried my luck on a suspended timber frame floor with UF between the joists and got stung! Big crack right up the middle of the public bathroom tiled floor.. that lined up with the bog pan.. it was the first thing you saw when you sat down for a "rest". At least it was my own self build.. but if that had been for a Client!

 

In the past we used smaller tiles and they were a bit more forgiving. I have these large format ones in parts of my house. They are expensive and not easily replaced thus followed @nod advice.

 

Yes a tiling matt is a heat barrier.. but as I have said before a lot of this stuff is about compromise.. we like rugs on the floor which insulate the UF.. pragmatism needs to prevail. 

 

 

 

 

[saveasteading]

47 minutes ago, Gus Potter said:

on a suspended timber frame floor with UF between the joists

I have used a different method over wonky old timber, Thin ply once, and marmox another time.

[Gus Potter]

18 minutes ago, saveasteading said:

I have used a different method over wonky old timber, Thin ply once, and marmox another time.

That is good design. You use every tool in your designers box to suit the build and play to the Clients strengths. Often the "old schoool" methods work very well.

[Conor]

On 02/10/2024 at 09:57, JackofAll said:

 Currently under pressure to get kitchen in as we've postponed it several times due to hold-up's at various stages of the project.

 

 

 

Install the kitchen now, directly on to the slab. Forget about the flooring. Leave the kickboards off and the tilers can tile up to and around the unit legs. Leave a gap under any gable ends. This is what we have done. If your tiler complains, get another one.

[JackofAll]

My preference would be to tile the whole floor and sit kitchen on top rather than tiling under units also don't fancy having to lift/move stone worktop to accommodate tiles if moving the units is an option. Looking like fitting kitchen first is the only option, thanks @Conor @Gus Potter. BTW  the decoupling matting is .85mm thick, so not really that thick.