Mixed wood/concrete floor preparation

[Steve Evans]

Hi, firstly I'd like to thank the forum for advice with tiling my bathroom last year....still looks good and no cracks or tiles have fallen off!!

I'm now tackling the kitchen floor and would like some input as things are not straight forward... The kitchen is approx 5m x5m. 1/4 of the floor was floor boards. This has been ripped up, the joists replaced/strengthened and 25mm marine ply screwed down. The other 3/4 is concrete with I suspect, no insulation and has a slight gradient of 15mm. I've laid the height of the Ply to the highest part of the concrete floor. The plan is to tile the floor with a slate style tile (not chosen yet) and have electric UFH.

My plan is to use 10mm Marmox boards over the whole floor and UFH/Tile on to the boards. Does this seem OK or is there a better solution? The cost is very much a secondary consideration as I just want the job to be right.

I was looking to install the Kitchen units onto the Marmox boards has anyone done this or will the units be too heavy for the boards?

Will it be possible to take up the 15mm unevenness in the concrete floor with the adhesive when laying the Marmox boards or will I need to screed the floor first?

Any replies/advice much appreciated. Cheers Steve

 

[diamondtiling]

The units will just damage the marmox sheets, I take it you are going to tile the whole floor and then fit the kitchen? In my opinion this is always the best way.
I would level the floor with a flexible one part SLC, its quicker than having to build up with adhesive, once done fix the insulation boards and cover the UFH with SLC, you will need an expansion gap between the timber and concrete and to be on the safe side use a de-coupling membrane.

 

[Steve Evans]

Thanks for the quick reply. I wasn't going to tile the whole floor as there are lots of units and there didn't seem to be much point in tiling under them, but I can do. The idea of putting the Marmox boards under the units was to add some insulation to an uninsulated concrete floor, but it's no good if the units will compress them.
How much depth would adding a SLC over the Marmox boards and a de-coupling membrane add? Correcting the floor, adding a 10mm Marmox board and say a 10mm tile will already have increased the height by 35-40mm. I was also hoping to get away without expansion joints as this will leave 2 random lines across the kitchen floor. I was hoping it would be OK to lay the Marmox boards so they span the wood and concrete and use a flexible adhesive. Cheers Steve

 

[diamondtiling]

Spanning the timber floor with marmox boards wont negate any movement that will naturally occur, a de-coupling membrane allows for movement without having an expansion gap on show. The slc over your ufh is just to protect the wires so that if you have a broken tile in the future it will be easier to replace, it will also help with the heat retainment. This slc will be as deep as your wires, about 4/5 mm.

 

[fox]

Hi there, my first post so go easy!
First of all apologies for hijacking the thread but I have a similar situation to Steve and would appreciate your advice.
The area of my kitchen is approx. 20 square meters and the bulk of this is made up of 22mm OSB on joists. My problem is that I have a small area of concrete approx 1.5m x 1.0m where the old chimney hearth is, and where a range cooker will sit. Following the advice above, would I need to provide a decoupling layer over the full area of the kitchen? Or, could I be more economical and use it locally to the chimney breast with say an overlap of approx. 1m onto the timber floor? I appreciate I would have a discrepancy in levels but could this be made up with more adhesive? or is there alternative approach that I have overlooked? I am keen to reduce the floor make up thickness as much as possible as mrs fox wants 25mm thick tiles with wet UFH of approx.18mm thickness.
Any advice would be much appreciated.

 

[doug boardley]

Spanning the timber floor with marmox boards wont negate any movement that will naturally occur, a de-coupling membrane allows for movement without having an expansion gap on show. The slc over your ufh is just to protect the wires so that if you have a broken tile in the future it will be easier to replace, it will also help with the heat retainment. This slc will be as deep as your wires, about 4/5 mm.

If an expansion joint is needed (which in this case it is) I'd still bring it to the surface rather than de-couple over it Dom.

 

[jay]

agree Doug all expansion joints must be carried through to the surface

 

[fox]

Thanks for your replies gents, 1 other quick question:
Our local Stax trade centre stocks evo-stick 'tile-a-floor' adhesive, I've searched the forum and not found any reference to it. Have you any opinions on the suitability of this product? link:
Evo-stik Tile A Floor - Stone & Porcelain - For stone & porcelain tiles

Cheers Rob

 

[doug boardley]

yep Fox.....leave it on the shop shelf!

 

[diamondtiling]

If an expansion joint is needed (which in this case it is) I'd still bring it to the surface rather than de-couple over it Dom.

I think I would be a bit aloof if I did not hold my hand up here and admit to a mistake.

Thanks Doug for clarifying my error, it is a good job that I have never had to tile over wood and concrete because it might have failed. That info has been logged in the grey matter.

 

[Steve Evans]

Thanks for the replies. If I use expansion joints I assume this means I don't need the decoupling material. So what's the best way to keep the joint visibly to a minimum, ideally so it won't be seen. Cheers Steve

 

[DHTiling]

Is the joint between timber and concrete a straight one..?

 

[Steve Evans]

Is the joint between timber and concrete a straight one..?

The joints will be straight but it will create 2 random lines across the kitchen floor, something I was hoping to avoid or at least hide as much as possible. Cheers Steve

 

[DHTiling]

Steve post a pic of it please..

 

[Steve Evans]

Not great pics but hopefully make it a little clearer...