Cement skim render?

[surreywill]

Hi all!

Doing bathroom at moment and have removed all the crappy old tiles from the walls.

Mrs. surreywill wants new tiles only in wet areas, and rest of the room painted. Suits me as less tiling to do and cheaper.

The newly tiled areas are being stripped back to brick, cement backing boards up, etc. - all done nice and proper.

However, I'm scratching my head a little on the rest of the room. Mostly the old tiles came off very well, but there's a few large areas where the old surface came off with the tiles and left the base render exposed. I reckon after removing all the unsound areas I'm left with maybe 2 or 3 m^2 to patch with a suitable material.

I feel like re-boarding the whole room is taking it too far.

The old surface looks like some kind of cement-based skim. My reasoning: it's grey
It's about 2mm thick. I've attached a pic.

Anyone know what it is and what I should patch with?

I'm very comfortable skimming with gypsum, but something tells me the edges won't "blend" in well with the grey stuff. Besides, is gypsum surface not recommended for humid areas like bathroom?

I'm not stressing too much about this as it's just walls but any thoughts welcomed.

SW.

 

[ree]

The skim has not bonded with the float - there is no corner bead - the scratch marks would indicate a DIY job.

If in doubt about the finish then see how much skim you can remove with a spatula scraper - prise the skim off in small sheets. If most comes away then remove it all and start from scratch.

If you want sharp corner(s) then cut back just enough to set the plastic bead(s) and fill in with a little sand and cement or multi.

PVA the field twice, first PVA wash to dry, and on the second, tacky PVA cover start skimming with say board finish.

If you have to work up to the old skim then knife cut straight lines to work to, and well water/soak the surface at the old edges - dont allow new skim to sit on the edges. Go heavy on the trowel at the edges.

 

[Micilin]

Old skim onto sand and cement.

No beads back then, generally, rules and external twitcher did those arrives.

Not sure why it would look like DIY, Rees, just looks like old devilling to me?

PVA should be fine, but if there is danger of moisture use SBR or something like Bondit.

Take off loose as suggested.

 

[surreywill]

Thanks both.

Sounds like Ree is saying gypsum is okay to use - Micilin, you agree?

Yes Micilin, I don't think it was DIY - the skim which did stay bonded was a flawless surface and the corners were really tight. Not sure a DIYer would have managed that level of finish.
(I - as a lowly DIYer - have made numerous attempts at external corners without beading before and I am in awe of anyone who can do it)

Thanks for tip about SBR, I'll have some spare anyway.