laying down ply.

[winston6705]

Not being to experienced, i would like to ask if laying ply over this compressed chipboard stuff they now use for floors instead of boards is a must? I am laying ceramic floor tiles.

[Sir Ramic]

If you can give more details on what type of tile you will be using and the present state of the chipboard floor. What area will be tiled etc. The more info the better.
If you are feeling any bounce in the floor then it will need strengthening in some form.

[winston6705]

HI the tiles are 330mm by 330mm and 8mm thick ceramic. the chipboard flooring is solid no noticable give and is 2m by 3m.

[Sir Ramic]

The BS is 15mm ply but in reality 15mm is hard to find so 18mm is used. You could use tile backer boards this come in 6mm and 10-12mm but i dont believe they add any strength.
Depending on what method you use would determine what adhesive you used. Tiling direct to chipboard can and has (with the correct adhesives and grouts) been done but i prefer not if it can be avoided.

[medlar]

i am with Sir Ramic on this one,ply over your chipboard then tile mate,dont forget to use flexi addy and grout,i would screw the ply at 200mm centres

[Rab78]

You could lift the chip board and strengthen it with extra beams and wedges, bolt everything onto the concrete base with hammer in screws. I did this for a 120m2 chipboard floor job, couldnt use ply due to cost/time and raising restrictions. It took time but i just set the joiner a couple days ahead of me and guided him along the way. Was way less messy than the extra woodwork.!

Use a 2-part flexi or 'tile on wood' after bonding with 1part water to 2parts bonding.

use a wide joint flexi grout.

[doug boardley]

I'm with Sir Ramic also on this one

[silver]

I have found different scenarios with chipboard...Having tried and really struggled to lift old tiles off a chipboard floor.....on one occasion. Never tiling onto chipboard didnt stack up in that case.....wonder what they were stuck with ?
But to be sure I never tile directly onto it. If there is no structural movement underneath (knacked joists) or "spring" Re board over with ply or Hardibacker, use SPFRS and away you go....as is the good advice you the guys have already given.
A tip I was given is that its not the adhesive that fails on the chipboard...its the breakdown of the fibrous surface of the chipboard, brought about by water / moisture ingress . Small 1>2m floors and false back walls behind cooking hobs made from chip board can be tanked to stop the moisture reaching the chip board and breaking it down.
Though I have only used this when raising the floor level by boarding out is a problem.

[grumpygrouter]

I have found different scenarios with chipboard...Having tried and really struggled to lift old tiles off a chipboard floor.....on one occasion. Never tiling onto chipboard didnt stack up in that case.....wonder what they were stuck with ?
But to be sure I never tile directly onto it. If there is no structural movement underneath (knacked joists) or "spring" Re board over with ply or Hardibacker, use SPFRS and away you go....as is the good advice you the guys have already given.
A tip I was given is that its not the adhesive that fails on the chipboard...its the breakdown of the fibrous surface of the chipboard, brought about by water / moisture ingress . Small 1>2m floors and false back walls behind cooking hobs made from chip board can be tanked to stop the moisture reaching the chip board and breaking it down.
Though I have only used this when raising the floor level by boarding out is a problem.

I think you are absolutely correct here Silver. If the chipboard is solid (no bounce) then the only reason to to overboard is to protect from moisture ingress. BS recommends over boarding to add strength to the floor, not to stop moisture getting at the boards. Certainly with small floors, as long as they are solid, I am happy to tile straight onto if if need be. Some customers just do not want the extra expense.

It is certainly better to put down at least something like 6mm Hardie Backer, or even tank as you suggest than not at all, but some times you are just not given the option.