mixed substrate floor

[MTiler]

Hi

I went to see a job today that I need a bit of advice on. The three floors to be tiled were mainly of concrete but sections had been chased out for radiator pipes and covered with ply. Its not as if one half is ply and the other concrete.
The size of the floors are: 8.56m2, 2.42m2 and 1m2 and theyre looking at 300mm or 400mm square tiles.
Whats the best way to prep the floors for tiling?

Cheers
missyT

 

[jay]

hi by chased out for pipes are theyabout 100mm wide by depth can the ply be removed and filled with concrete or render :8:

 

[Ajax123]

hi by chased out for pipes are theyabout 100mm wide by depth can the ply be removed and filled with concrete or render :8:

took the words right out me mouth..

 

[hillhead]

Is there some way to possibly place some segregation barrier over the ply and wider, light enough to not need extra depth of adhesive?wire mesh or similar?

 

[DHTiling]

Just uncouple it.... then you can tile straight away..

 

[hillhead]

Just uncouple it.... then you can tile straight away..

Ditra?

 

[DHTiling]

Ditra?

which ever.. as long as no deflection in these bits then ye!!

 

[White Room]

If you put any cement on copper pipes put tape over them, cement attacks copper over the years.

 

[hillhead]

i was well impressed with ditra last saturday,57ft long walkway by 3'7" wide! ran it down the whole way and layed 450x450 porcelain on it 2 hours later.25mm ply under it all.

 

[DHTiling]

The thing is here if you fill them, is that you still have fresh areas that will expand and joints in the screed at these areas that can cause cracks in the tiles..
So IMO needs uncoupling.

 

[jay]

interesting:8:

if the chasing only removes portion of the concrete and doesnt cut all the way through then you fill with concrete or render wouldnt the cracks that apear when dry only be shrinkage creacks from drying out quick there for a normal c1 adh should be able to cope

 

[DHTiling]

interesting:8:

if the chasing only removes portion of the concrete and doesnt cut all the way through then you fill with concrete or render wouldnt the cracks that apear when dry only be shrinkage creacks from drying out quick there for a normal c1 adh should be able to cope

But the pipes are heat/hot...?.. So forced expansion..

 

[jay]

thanks Dave take it you dont lag (insulate black foam linning) hot water pipes in concrete over there my mistake but ive learnt something :8:

 

[DHTiling]

Yes jay... some do..

but my overkill on the floor maybe.. but as a method to get straight on with it for misstiler, then an uncoupler would work and no infill drying times..

 

[Time's Ran Out]

Uncoupling was my thought - but are you suggesting just over the plywood areas with an overlap onto the concrete (my choice) - or uncoupling the whole floor area.
Certainly agree that by filling the chases with another mix would cause shrinkage.

 

[peckers]

In the past when this situation has arrived as long as the ply over the pipes area is firm and solid what i have done is used the schutler kerdi mat to bridge over the top of the ply and over the screeded area by 100mm each side. Im not saying it is the perfect solution but i have done this many times and havent had a problem. I always use single part flexible in this situation for the entire floor.

 

[MTiler]

Cheers for all the replies.
Putting Ditra over the whole floor (obviously securing the ply) did cross my mind but wasnt 100% sure that was the best option.

missyT

 

[DHTiling]

Uncoupling was my thought - but are you suggesting just over the plywood areas with an overlap onto the concrete (my choice) - or uncoupling the whole floor area.
Certainly agree that by filling the chases with another mix would cause shrinkage.

Both ways john... both work and each job needs to be taken at their own face value..

i.e. what are the risks..

I have seen a few floor jobs where a crack appears in a line and on closer inspection it is in a break in the floor( like patching in etc) or cracks.

But the main thing here is the radiator pipes( heat) ...if the plywood sections are narrow and well fixed then even a crack isolator would suffice..

 

[MTiler]

Both ways john... both work and each job needs to be taken at their own face value..

i.e. what are the risks..

I have seen a few floor jobs where a crack appers in a line and on closer inspection it is in a break in the floor( like patching in etc) or cracks.

But the main thing here is the radiator pipes( heat) ...if the plywood sections are narrow and well fixed then even a crack isolator would suffice..

crack isolator?

 

[DHTiling]

crack isolator?

Kerdi or dural wp.. or pci pecilastic , all are crack isolators as well.

 

[peckers]

Kerdi or dural wp.. or pci pecilastic , all are crack isolators as well.

I use the kerdi one not the cheapest but has always worked

 

[MTiler]

So if I was to use Kerdi matting as a crack isolator do I cover the whole floor, or just over the ply overlapping onto the concrete?

cheers for the advice

missyT

 

[peckers]

So if I was to use Kerdi matting as a crack isolator do I cover the whole floor, or just over the ply overlapping onto the concrete?

cheers for the advice

missyT

I would use it to just bridge over the ply over the pipes and onto the screeded area, not the whole floor.

 

[Sean Page]

I would use it to just bridge over the ply over the pipes and onto the screeded area, not the whole floor.

same here

 

[MTiler]

Sounds like a cunning plan to me.
Think I'll go for the Kerdi option.

Cheers for that

missyT