Tiling a room with multiple sub floors

[peterparker]

Good morning

I'll be having my kitchen tiled in the very near future. It is about 8.5m by 8.5m. It has two different kinds of subfloor ie suspended timber and solid concrete.

The suspended section has been reinforced with plenty of noggins and then over boarded with 22mm ply.

The two floors meet in more than one location (hopefully the pics show this)

The tiles are 900 x 900 porcelain, I'll be using mapei keraquick mixed with latex plus)

I'll be having electric ufh installed as well, if that makes a difference.

My questions are (I'm a homeowner not a tiler btw so bear with me please)

1) I'll be using ditra mat on the suspended section. Shall I put it down on the concrete as well? If not then do I make up the height difference by just using more adhesive on the concrete section?

2) Are there any other precautions I should take where the two floor types meet to prevent the chance of cracking?

Thanks very much for helping.

 

[nybor62]

what is the height difference, i would be self leveling over the heating mat, the suspended floor wouild be an issue for me , chance of failure is high imo

 

[peterparker]

what is the height difference, i would be self leveling over the heating mat, the suspended floor wouild be an issue for me , chance of failure is high imo

There is no height difference at present between the floors. What I meant was that if I only put ditra on the suspended floor this would then create a small height difference ie due to the thickness of the ditra.

You say there is a high chance of failure, does that mean you should NEVER tile over a suspended floor?

 

[Rich Midge]

Morning! Ideally you should be using expansion strips over the joins in the subfloor though I appreciate these are often ugly especially when using rectified porcelain and a narrow grout joint. My method is as follows, right or wrong I don't know, sure others will have their say, but its not let me down yet! I carry the ply over the concrete by a couple of foot, glued and screwed down. Then insulation boards onto the concrete to meet the ply (leveller may be necessary to match the height) then I use Dural CL over the lot. In your case I'd also suggest heating the timber and concrete areas independently. Hope this helps.

 

[Dave]

The issue is where the timber meets concrete , as each substrate will expand at differing rates and the timber section will also slightly deflect .

At this point IMHO , you should insert a movement joint , matching it as close as you can to the grout colour , if possible start a full tile from either side of it for the best aesthetics but this will depend on how the tiles fall to other areas .

On the timer section Ditra would be ideal to combat stress at the board joints and you can go over the whole floor or Ditra the timber and SLC the concrete , which ever way on the concrete that works out cheaper ... I would just Ditra the whole lot if I was doing it..

hope that helps.

 

[Dave]

Missed the UFH bit there.... Yep slc the whole floor...

 

[peterparker]

Morning! Ideally you should be using expansion strips over the joins in the subfloor though I appreciate these are often ugly especially when using rectified porcelain and a narrow grout joint. My method is as follows, right or wrong I don't know, sure others will have their say, but its not let me down yet! I carry the ply over the concrete by a couple of foot, glued and screwed down. Then insulation boards onto the concrete to meet the ply (leveller may be necessary to match the height) then I use Dural CL over the lot. In your case I'd also suggest heating the timber and concrete areas independently. Hope this helps.

Thanks for replying Rich.

Do you carry the ply over the concrete to help with differential movement where the two meet?

Given that I now have ply at the same level as the concrete what are my options if I wanted to use your method?

Btw, I've googled dural CL and nothing comes up

 

[peterparker]

The issue is where the timber meets concrete , as each substrate will expand at differing rates and the timber section will also slightly deflect .

At this point IMHO , you should insert a movement joint , matching it as close as you can to the grout colour , if possible start a full tile from either side of it for the best aesthetics but this will depend on how the tiles fall to other areas .

On the timer section Ditra would be ideal to combat stress at the board joints and you can go over the whole floor or Ditra the timber and SLC the concrete , which ever way on the concrete that works out cheaper ... I would just Ditra the whole lot if I was doing it..

hope that helps.

Thanks for helping David.

Any idea of what size expansion joint I should use?

Also, is this basically what you are suggesting?

1) Electric ufh stuck to the ply and concrete using flexible tile adhesive (Keraquick + latex)

2) Then slc the whole floor, ie no ditra anywhere.

3) Then tile using flexible adhesive whilst ensuring to leave an expansion joint at the timber/concrete interfaces?

Many thanks for your help

 

[Rich Midge]

Hi Peter, yes I carry the ply over to strengthen the transition. In your case, if the ply is level with the concrete I'd use an insulation board (marmox or similar) over the whole floor. If there's still pennies in the budget then use the ditra as well. I always if possible use the belt and braces approach! It's harder to fix a floor that's failed than to prep it right at the start. Dural is similar to Ditra.

 

[Dave]

Thanks for helping David.

Any idea of what size expansion joint I should use?

Also, is this basically what you are suggesting?

1) Electric ufh stuck to the ply and concrete using flexible tile adhesive (Keraquick + latex)

2) Then slc the whole floor, ie no ditra anywhere.

3) Then tile using flexible adhesive whilst ensuring to leave an expansion joint at the timber/concrete interfaces?

Many thanks for your help

You use a pre-formed expansion/movement joint , I would also zone the 2 areas and not bridge UFH over the break in substrates .

 

[widler]

Thanks for helping David.

Any idea of what size expansion joint I should use?

Also, is this basically what you are suggesting?

1) Electric ufh stuck to the ply and concrete using flexible tile adhesive (Keraquick + latex)

2) Then slc the whole floor, ie no ditra anywhere.

3) Then tile using flexible adhesive whilst ensuring to leave an expansion joint at the timber/concrete interfaces?

Many thanks for your help

You don't put eufh straight onto concrete, well you can, but you be wasting a lot of penny's , you would be heating the concrete as well as the tiles .

Insulation boards, eufh matt, SLC ,, tile, I wouldn't put a expansion bead in it, they are fine in commercial buildings, but in your kitchen would be very ugly .
Where you would put the ugly bead, I'd just tile as normal and silicone where the ugly bead was going in same colour as grout ,hey presto your very own home made expiation bead [emoji106]

 

[Spud]

The biggest issue you have there is the massive island unit it mostly on the suspended side and if you have stone work tops you will be putting the suspended joists under a lot of load , I would double check before you start the tiling job that as well as noggins you have piers under the joists otherwise your floor will fail

 

[peterparker]

Thanks

I'm pretty sure there are piers, it feels rock solid, but I will ask the builder tomorrow. Two things I'm still a bit confused about

1) Is the reason for not bridging the ufh across the substrates because it might fracture with the differential movement?

2) Do I need to leave an expansion gap or not? With most other things, even if it adds cost, I would just go belt and braces for peace of mind. However an expansion gap will obviously have a negative visual effect so I only want to do it if I really have to.

Thanks again

 

[Rich Midge]

If you go with the method I described you should be ok to go without expansion strips. Marmox or similar insulation boards over the whole floor, staggered joints. Heater cables, leveller, ditra, tiles. You could lay the heater cables on top of the ditra in which case I'd go, marmox, ditra, leveller, heater, leveller, tile. Good luck.

 

[Sean SML Tiling]

Why don't you look at ditra heat which is ufh with ditra matting. You don't need the slc over the top then. Save you some money. I also would use expansion where substrates meet.

 

[peterparker]

There is some good news and I think some not so good.

The good news is that one section of the timber floor has three piers, ie one at either end and one in the middle.

The other section of timber floor has a short span ie 2.5m but looking at the ply I don't think the joints are what you guys call staggered. I've attached a photo, could somebody please comment?

Thanks

 

[White Room]

Where your brick piers are I would allow for a control joint, the timber either side could at some stage move/flex/drop...

 

[peterparker]

Where your brick piers are I would allow for a control joint, the timber either side could at some stage move/flex/drop...

If I put control joints where all the piers are AND where the timber floor meets concrete I will end up with about five long expansion joints in my kitchen!

I appreciate what you are saying but my floor will end up looking like a dog's dinner won't it?

 

[White Room]

If I put control joints where all the piers are AND where the timber floor meets concrete I will end up with about five long expansion joints in my kitchen!

I appreciate what you are saying but my floor will end up looking like a dog's dinner won't it?

Just one control joint along all the brick piers....

 

[widler]

Ha ha ha [emoji23][emoji23]way this threads going,the blokes gonna sell his tiles and laminate it [emoji23][emoji23][emoji23][emoji23][emoji23][emoji23]

 

[peterparker]

Sorry to resurrect this thread again.

Over the last week or two I've taken quite a bit of time to further reinforce the timber floor sections. There are now further noggins and timber 'feet' that are screwed to the joists and then sit on concrete below.

My plan, after advice from here and elsewhere, was to put a control joint where timber floor meets concrete. However having discussed this with my tiler he feels that this is not possible.

The reason being that the timber/concrete interface is nowhere near a straight line and so the tiling pattern would look awful if the control joint was to follow this interface exactly.

So my question is...would it still be worth putting an expansion joint in if it is just close to the timber/concrete interface? ie it would not follow the line of the interface exactly, at some points the control joint might be 4-5 inches away from where the floors meet.

Many thanks for your help

 

[Spud]

Sorry to resurrect this thread again.

Over the last week or two I've taken quite a bit of time to further reinforce the timber floor sections. There are now further noggins and timber 'feet' that are screwed to the joists and then sit on concrete below.

My plan, after advice from here and elsewhere, was to put a control joint where timber floor meets concrete. However having discussed this with my tiler he feels that this is not possible.

The reason being that the timber/concrete interface is nowhere near a straight line and so the tiling pattern would look awful if the control joint was to follow this interface exactly.

So my question is...would it still be worth putting an expansion joint in if it is just close to the timber/concrete interface? ie it would not follow the line of the interface exactly, at some points the control joint might be 4-5 inches away from where the floors meet.

Many thanks for your help

I missed a construction joint in a concrete floor by 15 mm once , big mistake tiles cracked over the joint even with a preformed expansion joint I had poorly placed ,I had to take the tiles up and re align the expansion joint , so my advice is follow the joint between the 2 substrates

 

[Rich Midge]

I agree with above. You either follow the joint exactly or find a way of getting over it (see my previous replies)

 

[Houston]

for me 2 different substrates means expansion joint and is your set out point

 

[Spare Tool]

Sorry to resurrect this thread again.

Over the last week or two I've taken quite a bit of time to further reinforce the timber floor sections. There are now further noggins and timber 'feet' that are screwed to the joists and then sit on concrete below.

My plan, after advice from here and elsewhere, was to put a control joint where timber floor meets concrete. However having discussed this with my tiler he feels that this is not possible.

The reason being that the timber/concrete interface is nowhere near a straight line and so the tiling pattern would look awful if the control joint was to follow this interface exactly.

So my question is...would it still be worth putting an expansion joint in if it is just close to the timber/concrete interface? ie it would not follow the line of the interface exactly, at some points the control joint might be 4-5 inches away from where the floors meet.

Many thanks for your help

I did a 30sqm floor over 2 years ago with exactly the issues you have Peter, ie ply meeting concrete at various points with ufh, also used 600x600 porcelain on that job...
Installed insulation boards over whole floor, thinking back they weren't marmox boards just the cheap blue foam type the customer supplied which could help to uncouple the substrate(not a substitute for uncoupling I know but can only help) then 150watt heating matts zoned over kitchen and living area, webber fibre flexible leveller over the lot, ditra the whole floor, expansion joints as near to joins in substrates as possible, these were marked on the wall before tiling. The expansion joints were mapie matching silicone to the grout used, which were hardly noticable... Last year I went back and tiled his bathroom and utility room and his patio and they're had been no problems with the floor whatsoever and I have heard of no problems with the floor since, and the customer owns a big plumbers merchants local to me that I'm in and out of so if anything had failed I would have definitely have heard about it...can only speak from my own experience which I hold my hands up and admit isn't as much as some of the guys on the forum but the fact of the matter is after 2 years, no fails or cracks...
Andy