tiling a suspended floor

[paulb33]

Hi All,
We're having a new kitchen installed and scratching our heads over the floor, which is currently boards (previously carpeted, fairly damaged & wide gaps) on a suspended floor. We'd like to replace with tiles.

I'm thinking of lifting the boards, laying ply and tiling. Is this doable? Would movement be a problem?

Any tips would be welcome.
Thanks,
Paul

 

[BMcD]

you can lay 6mm ply over the existing boards and screw every 6" to keep from buckling and then add a latex additive to the tile adhesive and grout to help prevent lifting/cracking when the floor flexes

 

[paulb33]

Thanks for the tip. I should have said that we'd rather not have a step into the kitchen. Hence, we'd lift the existing boards.

 

[CHRIS]

You could pull up the boards (if not nice old ones) and lay 22mm ply and screw every 400mm along the joist, you could also run a nice dob of gripfill etc along the joist just as you lay the ply down for extra grip. You will have to think if there is any movement it will crack the grout so you may wish to consider some extra noggins between the joists.

Then do as BMcD says and use the flexible grout like the one from BAL.

http://www.trades-direct.co.uk/modules/shop/view.asp?Prodcode=2161-101

Whilst the floor is up consider adding extra insulation by using plastic netting between the joists holding fuzzy insulation, I did and it is much warmer and stops draughts, just dont block air bricks etc.

 

[inwood]

The tile association recommends 15mm WBP (Water and Boil Proof) plywood as a minimum for suspended timber floors. As Chris has suggested I would use 22mm ply. Don't forget that your kitchen is a fairly high traffic area. Any likely movement will be at the joints in the boards so concentrate on supporting and fixing these.

1. Lay all boards with staggered joints (i.e. the same as bricks in a wall).
2. Ensure all joints between boards are supported by joists or noggins.
3. Screw the boards to the joists/noggins using large headed screws such as no. 8/10's (i.e. not chipboard screws).
4. The tile association recommends screwing at 300mm centres - I'm paranoid and screw at 200mm centres.
5. I also screw down between the joints in the boards as well (from bitter experience).
6. Ensure you leave a 10mm gap around the perimeter of the room for expansion (even ply expands with temperature changes).
7. Countersink the screw heads (avoids any tile being supported on a screw head and causing a weak point).
8. Use a good quality flexible adhesive and grout (BAL adhesives are very good) - I source mine from my local independent tile shop - they are also great for advice.

If you do end up with a slight lip at the doorways you can cut a piece of timber and fix this to the ply as a threshold before grouting.

The old adage that it's all in the preparation really does apply when it comes to tiling suspended timber floors if you want to avoid cracked tiles.