Awkward window reveal disaster

[Steve]

As you can see from the pictures, I have had an issue with the window reveal in the bathroom. The reveal is plastic, and has been tiled before - the score marks were made by the previous tiler.

The two tiles that today fell off were stuck on on friday.

I have hacked most of the plaster off, but the plaster around the window was new and sound, so what I did was hack off the old plaster and fill i the gaps with a board, then overboard the whole lot - in effect making the wall slightly thicker.

The plastic reveal is at an angle of around 75 degrees to the wall. So to straighten it off, when I dot n dabbed the surrounding wall, I extended the plasterboard over the window reveal slightly, to get a good 90 degrees to the window frame. So now I have a deep recess to get my tiles over. I originally stuck the tiles on with a good chunk of adhesive (Mapestick). But when they fell off it is still wet at the back!

An idea I had was to stick a piece of tile onto the deepest part of the reveal, then stick the proper tile over it. But I have a feeling the real problem here is absorbency of the plastic reveal.

Any tips? I could do without taking off the reveal. It was tiled before, for 9 years. I think they used cement though.

Pictures:

Untitled

• Steve
• 21 Jan 2013
• 1

Untitled

• Steve
• 21 Jan 2013
• 1

Untitled

• Steve
• 21 Jan 2013
• 1

 

[jctilingservices]

what is the depth you have to overcome mate, can you not just fix the tile in place with a rapid set addy ?

 

[Steve]

Deepest is about 15-20mm, just behind the PB and tile trim. Shallowest is by the window, standard depth for tiling.

 

[Burnerman]

Can you fix some sort of packing material into the back of the reveal using screws, and then tile on to that?
Maybe an adhesive made up from powder (rather than ready mixed) would be better....I believe it chemically dries rather than by air or absorption.
John

 

[Steve]

I've got some 12mm ply knocking about, I'll put some of that in the hole.

 

[tictic]

12.5mm plasterboard then bed out with powdered addy..

Is the ply wbp ??