floor tile adhesive

[Graham & Brenda]

I am about to lay ceramic floor tiles in my bathroom and have covered the floorboards with hardboard. Having just read the instructions on the adhesive packet [Cercol F16, for use on cement substates] it says not to use on wood - amongst other things. Can I salvage the situation by first sealing the hardboard or do I need a completely different adhesive? Alternatively is it OK to use anyway? [All I did was tell the chap in the shop what tiles they were, not the surface I was to lay them on and I chose a dry product rather than ready mixed having seen the prices!].

Thanks for any advice,

Graham

[Jackie]

Sorry cannot really help with the adhesive other than to say that Castorama suggested a sealing agent before laying the tiles. The point I did want to comment on is that you say you have used hardboard to cover the floorboards. Are you sure that this is rigid enough? Some sites suggest you use 12mm ply and when I did a bathroom here recently I used 15mm plywood with lots of screws everywhere. I could not find marine ply so sealed it with the stuff castorama suggested. They also recommended a slightly flexible adhesive, no problems so far......Hope this might help...........John in 79

[Bobc]

I have posted the answer to this several times in the past but they are probably lost in the changeover.

If you are planning on tiling over old floorboards then the subfloor must be 99,9% rigid.

Hardboard will not do the job. You need to use a hydrofuge treated OSB board such as Eurostrand which you then glue (with construction adhesive) and screw to the old floorboards.

The next stages are then done with products from Weber et Broutin which are available from any good professional carrelage supplier - forget the brico sheds and Castorama.

Seal the floor with Iboprim.

If it is for a bathroom or kitchen further seal with Fermasec.

Fix your tiles with Fermaflex Technic

Joint your tiles with Fermajoint Souple.

In addition to the above I normally seal all the joints in the floor panels and floor/wall joints with rubber tape bedded in tile adhesive.

For your reference, all good floor tile adhesive comes in powder form. The best wall and worktop tile adhesive is Fermafix Plus - best value in the 25kg bucket.

Regards,

Bob Clarke
http://perso.wanadoo.fr/grindoux