having porcelian floor tiles n bathroom is it ok for builders to fit directly ontofloor boards

Never use PVA,prime with SBR such as Bal Bond have used this product for some decades now,I have had no problems, apart from that the rest of the advice given is correct.

Categorically NO !!!,although a number of adhesives are now on the market purporting to be suitable for this job I cannot stress strongly enough the need to keep away from such products and protect your investment by doing the job properly first time. Minimum requirement sub floor would be 12mm wbp ply screwed down with screws no more than 9 inches apart and sealed witheither an acrylic primer or (dare I say it)PVA and use a good flexible adhesive such as Bal Superflex,my preference for sub floor is either 18mm ply or 12.5mm Hardi Backer screwed down nice and tight. Good luck with the tiling

no no no no no

Hi Kim, No you cant fit tiles onto floorboards as they all flex seperately.You need to make sure all floorboards are fixed securely,then lay down 15mm ply and screw it down every 100mm.You then must use a flexible adhesive & a flexible grout. Hope this has been of some help. Steve PRO-TILE

I5mm is the MINIMUM thickness ply according to british standards (there are other materials suitable though) and although suggested by others, using pva is NOT a good idea.If any builder/tiler suggests going straight on the floorboards then theres a good chance that he doesnt know his a*** from his elbow.I can guarantee that you are going to have problems with this floor if this is how its done.If your proposed tiler wants to use bal or ardex materials then whilst he might be more expensive,he knows what he is talking about.Steer clear of wickes,and b&q etc as their stuff is crap.

as long as the correct adhesive is used, they will need flexible adhesive for porcelian or natural stone, and they will also need to prepare the floor first eg if the floor boards are uneven they will need some plywood screwing down first and then the floor will need sealing with unibond or cheaper bit just as efective is pve glue and water mixed about 4 to 1