preparation for tiling a wooden floor

Hi

I am shortly going to tile a wooden floor and was wondering about the preparation required.

I was planning on putting plywood over the existing floorboards, but am not sure what thickness to use.

My DIY book says 12 mm, other doucments say a minimum of 18 mm. Also what hole spacing is required ? Should the plywood be screwed
through the floorboards into the joists or just to the floorboards ?

any help would be appreciated

simon

It's best to put in extra screws in the floorboards (check for cable wires & pipe) then use 12mm plywood and screw it down every approx' 9" (230mm) to the floorboard will be okay. Make sure the length of the screw is no more than the thickness of the plywood & floorboards.

18mm is too thick unless you're removing the floorboards and just use that instead.

thanks for the info

I was hoping 12 mm would do as it is a bit cheaper

Forgot to add, use non-rust screws type

I have on a number of occasions used 9mm ply, but more screws are needed (6" spacing works). Make sure that the existing floorboards are secure and don't creak! You may need to drill out lots of pilot holes but a good battery drill makes short work of this. Cut the ply so that it is about 10mm smaller all around than the room perimeter, it makes it easier to fit. If you have radiator pipes coming up through the floor, cut out a 4 or 5" rectangle from the ply for fitting behind the pipe, to ensure that no large holes are left in the ply behind the pipe. If this is in a bathroom, check to see if your pipes are earth bonded before you start, as you could put the bond wire beneath the floor - ask an electrician for advice if you are not sure.