Tiling over different floor types in the same room...

[mattfran]

I am in the final stages of having an extension built to my ground floor kitchen. The existing floor is a timber floor (boards over joists) but the new floor will be concrete. The oversite is already poured, but we've yet to lay the insulation and screed over it.

I want to tile the entire floor once it is finished (thinking of 600x600 porcelain tiles), and to avoid the inevitable crack where the two floors meet my builder (who has only limited tiling experience ) has suggested we screed to the same level as the original kitchen joists, remove the old kitchen floorboards and then use decent plywood over the whole area.

My question is firstly how should we fix the plywood to the concrete floor (obviously it gets screwed to the joists in the old area) and secondly what type of plywood should we be using?

Or is this not a good solution at all and should we be screeding level with the timber floor surface and fitting some kind of expansion joint

 

[gcol]

You need to either replace the floorboards with 25mm WBP ply or overboard the existing floorboards with 12mm ply (read the sticky). Once you've sorted the kitchen, you'll need to screed the new floor to the same level. You'll also need to leave an expansion gap to allow for any dissimilar movement between floor types. You can use something like this http://www.geocel.co.uk/dynpdfs/217.pdf to fill the joint.

 

[mattfran]

OK, thanks for that gcol. So where I tile over that joint between the two surfaces I should make sure I have a grout line over that joint and fill the tile joint with this geocel? I really wanted it to look like one continuous floor, but if that's not possible... [/b]

 

[gcol]

Yep, that's it.

 

[yukisan]

Hi Mattfran,

I was looking for information about tiling over different floor types in the same room and end it up here. Your post is from long time ago so you might not even been active on this forum anymore. But if you are, what did you do???? i have exactly the same situation now. I hope you still around and that you can give me any advice.

Thanks

Yuki

 

[tictic]

re:tiling 2 differant subtrates

you will want to get them level,either by overboarding the wooden one,with either a cementbased backerboard..hardie,wedi,aquapanel ..etc..follow mfr instuctions.

or overboarding with min 18mm wbp ply..

make sure the floorboards are sound and in good condition first(no deflection at all)
or
rip up floorboards and replace with 25mm wbp ply.

if going for any off the wbp ply routes,you will want to prime the underside and edges with a sbr(stops moisture ingress from below)before laying them.

then you will HAVE TO PUT AN EXSPANSION JOINT between both subtrates,when it comes to tiling, as you will get movement in this area, as its 2 differant subtrates,you can buy ones from shulter etc or use a silicone that will match your grout colour.

leave 5-10mm gap around the perimeter of the room as well for exspansion,fill with silicone or exspansion joint, then put your skirting on.

re:conctrete/screed floor...
sweep this then prime with a sbr(m.i.) up the room then when dry across the room(100% coverage)..

as for priming the face of your wbp ply,this depends on what adhesive mfr you go with,follow m.i regarding this(some will say yes/some will say nae).

as for adhesive i would advise you just buy a flexiable one for the whole area,flexiable grout as well.

just make sure the wooden floor HAS NO DEFLECTION WHAT SO EVER..

 

[tictic]

almost forgot...when your leveling off..DONT butt the wbp/backerboard...up against the solid floor leave a gap 5mm+ between them.

 

[reggie13]

almost forgot...when your leveling off..DONT butt the wbp/backerboard...up against the solid floor leave a gap 5mm+ between them.

tictic,

just to clarify, after doing the ply (25mm or otherwise) :

do you screed over both solid floor and plywood to an even level and leave 5mm gap

OR

do you screed over the solid floor to the level of the ply , leaving a 5mm gap between the two edges ?