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Discuss 120 x 240cm Porcelain tiles over suspended floor (and UFH) in the Tiling Advice | Tile Forum area at TilersForums. USA and UK Tiling Forum

Shai

TF
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Hi All, I urgently need some advice and not sure where to turn.


We are having some major renovations in our house which includes an large open area 15m x 10m which would include the kitchen, living and dining room. The whole house (apart from the loft conversion) would be fitted with a wet UFH system. Its worth mentioning that the vast majority of the walls are being reconfigured/moved and all of the flooring is being removed.


The house is on a hill and the floors are all suspended floors.


When we fitted the kitchen that was in for the last 13 years, we realised that there was so much deflection on the floors when anyone bounced up/down on them. This was not rectified or improved much even when we buttoned (?) (sorry not sure of the correct terminology) the beams with cross pieces of wood and an 18mm plywood top. So we removed it all and started to support the beams with large pieces of timbre vertically down to the floor below. This improved the deflection massively but it was done by myself so not the most professional job out there. So we were left with the beams supported by the vertical beams at every mid-section of a large span and then the beams with the insulation board. Then the pipes were clipped to that and we then poured dry mix onto the that level with the beams. On top of the beams we fitted 18mm treated plywood and on top of that we fitted the porcelain floor using flexible Mapai https://www.tilersforums.com/forums/tile-adhesive/ and grout. (this was done by a tiler obviously not us)


Worth mentioning that the tiles were quite cheap 30x60cm.


To cut a long story short, 13 years later we have some slight movement in s couple of tiles (where you step on it and you can feel it) but nothing major. None have popped out or had to be replaced. We do however have 2 or 3 cracked tiles. Mostly due to kids dropping utensils or other stuff on them.


I would like to prepare myself with some advice before talking to the plumber and tiler on what is best practices these days. I obviously want the builders to spend some time properly supporting the floor throughout.

We have our hopes set on these amazing 120x240 porcelain (10mm thick) tiles. But, if you guys think im asking for trouble by going that route, we would consider 120x120 tiles although rectangle would look much better in that space.


So my questions are:

1. would you advise against such large format tiles if the floor is properly supported?

2. Do people still use dry mix to cover the pipes? We loved our UFH as even when it was off it was heating up the house due to heat retention. I just don’t see the heatplates that the plumbers seem to be recommending these days doing the same?

3. Can someone advise on how the layers should be set up from the ground up? I read around and saw that Ditramat can help with horizontal deflection (assuming due to expansion?) but does nothing for deflection? Is there anything else we should consider?

Apologies for the long post. Any advice or assistance would be greatly appreciated.
 
S

slythetiler

First thing i would consider, if you are doing a total rip out is to look at the feasibility of dropping some steels into the floor at regular intervals along the 10m side. I had a similar issue of a house renovation i was involved in, and the architect suggested steels to counter the deflection in the floor. Not a cheap option mind, but very good way of reducing the flex down to virtually nothing. Then build the floor finish in to run over the top of the steels. Drop the wet floor on top as per recommended by whichever system you are using. Finish it off with a good quality flexible https://www.tilersforums.com/forums/tile-adhesive/ and grout. I would make the grout lines over the steels as movement joints as an added extra to the floor. Anyone else like to chip in with advice?
 
D

Dumbo

I think you should be getting a structural engineer involved to figure out stresses on what you intend doing . For instance dry mix at a depth of 25 mm will add approximately 42 kilos a square metre to flooring which will stress your joist considerably .
 
O

Old Mod

Tiles, https://www.tilersforums.com/forums/tile-adhesive/ and grout will add another 30kgm2 approximately.

Whilst there is a lot of information in your post, it’s mostly historic, and doesn’t set out your latest plans. We can assume that the new ufh is a different system can we, as you mentioned what sound like
‘spreader plates’
What type of ufh system is it?
Is it a retro fit system like wunda floor?
Yes wet ufh is still encased in floor screed.
Is there no architect involved with your project?
Yes, correctly prepared, those tiles are suitable.
Yes Ditra matting assists with elimination of the effects of expansion and contraction of a floor.
And no, it will not guard against deflection.
It sounds like you’re a long way from knowing the benefits of Ditra matting tho.
If you want this to be the last time you rip everything out and start again, as above, an engineer seems to be the place to start.
Then if your floor develops issues in the future, you at least have a place to start from, take the word of a tiler or two in the reconstruction of your ground floor and it fails, you’ll have no one to blame but your Builder and yourself.
 
OP
S

Shai

TF
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4
Thanks for all of your advice guys. Some food for thought there.


Slythetiler – That’s certainly something I did not think about. Sounds like it would sort out the deflection issue. I have referred the question to the structural engineer to see if she can advise further.


Jcrtiling – Extra weight is something I did not think about. It makes the solution above to sound even more attractive.


3_fall – I suppose my vagueness comes from my lack of knowledge on what is about today. All I know is that it will be a wet system throughout. Names such as polypipe and others have been mentioned but to me none sound as good as pipes covered with screed.


There is an architect involved and a structural engineer but their deep knowledge of UFH systems goes as far as being able to recommend previous systems they have heard of.


I think that I like the idea of steels to fix the deflection issue and then that will also solve the load issue which would enable us to install an UFH system with screed on top rather than heat spreaders. The best thing about the old wet UFH screeded system was the consistent temp reached by low heat output to keep the space nice and warm.
 
OP
S

Shai

TF
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Plan attached...

L0_plan.jpg
 
D

Dumbo

Your structural engineer is the one who should understand the amount of weight involved and should make the recommendations on what size steels . What spacing and how many . How to support them . Engineering bricks or concrete lintels etc . If they don' get a new structural engineer
 

Chris Gibbs

TF
Arms
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177
maybe look at an anhydrite screed, it can be laid at about 40mm thick and gives a lovely even heat distribution. because its more than half the thickness of a concrete screed it will be a lot lighter too.
something else to ask your contractor.
 

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