At wits end - Tiles falling off Wood - Tried everything

[Ragworm The Abominable]

Hello All,

I'm at my wits end - and this post is a sanity check on what I have so far to rectify the problem.

I've tiled the bathroom - the last two parts to tile are 18mm marine ply for a boxed section, and 18mm flooring-grade chipboard, both in a vertical plane.

Tiling on the ply failed. So I tried PVA. This also failed. Then I tried spirit based undercoat for wood - the tiles were easily removed with a screwdriver.

The adhesive is a general adhesive & grout from Unibond. The adhesive after being allowed to set turns into a powerery substance and is easily removed from both the wood and the tile. The adhesive works perfectly on any other surface (testament to the 160 other 6'x4' tiles already up).

My theory is this - the spirit based undercoat still isn't acting as a barrier between the cement and the wood. My current course of action is to add another coat of primer, then top-coat with at least one layer of spirit-based gloss.

Having checked the archives, another avenue is to try a flexible cement based adhesive.

Is there anything else I should do or try? I need to get this sorted pronto before my wife leaves me for someone more DIY orientated.

Many thanks!

[Lobster]

How well supported are your wood panels? They need to be absolutely rigid, with no flexing. I've had the same problem as you in the past, which was cured by adding another supporting batten behind the panel.

David

[Ragworm The Abominable]

Hi David, thank you for your reply. I believe the wood panels are absolutely rigid. Even given them a good wack with my hand they move less than the internal walls.

[The Natural Philosopher]

You have used the worst possible adhesive.

Use Evostik waterproof, for one..I can guarantee this works a treat.

I am puzzled as to why you had a 'spirit based undercoat' on there though.

I tile onto the bare wood.

[Dave Plowman (News)]

Think the answer is to use a so called waterproof adhesive (suitable for showers etc - not swimming pools ;-)) - usually the next more expensive one in the range. It will take longer to dry fully, though, than on plaster. I've used it on wood, ply and MDF with some success - although there may be some movement between the 'wood' and a wall etc resulting in ordinary grouting giving way. But the adhesive holds. I'd just coat the wood with dilute PVA and make sure it's dry before tiling.

[Ragworm The Abominable]

Apologies, I've taken another look at the tub and it is a waterproof adhesive & grout.

As time is of the essence (wife about to drop a sprog) I've gone out and bought some Flexible 1 Part BS5980 Class AA Cement based adhesive suitable for Walls and Floors - setting time 2 hours. Picked this up from the local tile shop.

It says suitable for swimming pools ... (!)

Cost £17 for 10kg :-(

Any tips on using this type of adhesive as I assume it won't be as forgiving as the adhesive I've been using? Eg, may remove my fingers, probably won't come out of the carpet, and could be harder to remove from the front of the time.

Many thanks!

[Christian McArdle]

I would go for BAL White Star in this application. I am worried by the undercoat, though. A solvent based undercoat could possibly reduce adhesion. I would, at least, rub it down briskly with coarse sandpaper first.

Christian.

[Ragworm The Abominable]

I know that is it bad form to reply to my own post ... the adhesive with the cement base has done the trick - my two test tiles were firmly attached after just two hours.

Thanks to all that replied :-)

[robert]

I always think that posting an outcome or result is good form and very useful for other readers especially those searching in the future.

Robert Robert

[The Natural Philosopher]

Hear hear. For archival to be useful, one needs the problem, the reasoning behind proposed solutions, and the story of which worked, and why, and just as importantly, which did not.