Prepping a support beam for tiling

[P0cketGuy]

Hi
Complete newbie, so apols if this is a bit basic

Started tiling the bathroom and huge chunks of plaster fell off the outside wall, so started to prep for re-plastering. Noticed that the top section above the windows on this wall were 'leaning in' by a good measure, and the new tiles would therefore look odd (was previously wallpapered), so hacked this off to re-level and found a large wooden support beam running across the length of the wall.

To allow for the new tiles to stay in a rough vertical line, the lower section takes 12.5mm board OK, but the top (which leans in) has less than 6mm of depth available.

Given that this is an outside beam, sitting below the eaves and behind a soffit, how do I best plaster/prep this for tiling?

Appreciate any advice.
Cheers.

 

[Richard C]

You can’t tile over an unsound or damp base so you need to sort that out first; anything that is loose or sounds hollow must come off, what your left with will dictate how you proceed before tiling. You cannot plaster over wood, it will fall off &, generally, if your tiling don't plaster; it’s not necessary, reduces permissible tile weight (20 kg/sqm including addy & grout) & you will have to wait 10 to 28 days for it to dry before you can tile over it; tile weight could be an issue if you’re using large format tiles. Use MR Plasterboard to pack the beam out to the desired level, don’t attempt to use different thicknesses to save a few mm & the minimum board thickness you should use is 12mm. If you use PB in a wet area it must be tanked, better to use a waterproof tile backer board if you want it to last.

Read the Tiling Forum sticky & forum archive posts, it may prevent you making disastrous & potentially expensive mistakes. Use only trade quality tiling materials of the correct sort for your tiles & tile base, not cheapo DIY shed crap.