Plastering over mixed surfaces

I'm about to start plastering the inside of a little garden folly. It doesn't have a damp course, but I don't think it is subject to rising damp. The first 4' is built of reinforced concrete which at one time was sealed with a thin bitumastic compound (whatever they used in the seventies) which is still covering about half the area. There's a ring beam of very dense concrete above that. And above that, the construction is concrete blocks with a concrete render coat, very rough. The outside of the building is concrete rendered.

In the long term, I want to put in some rather fancy plasterwork with moulded designs. I think the first thing would be to create a reasonably uniform plaster surface, then add the fancy stuff. The plaster should be white or white-ish---so it has the look of old lime plaster.

Is there a kind of plaster that will do this job? How do I prepare the various surfaces? I hope that a coat of PVA or SBR (or something else?) would be all that's needed to help new plaster stick on. Or is it better to try to get rid of the black stuff?

Reply to
blod
Loading thread data ...

I'd use lime plaster, tho doubt anything will stick to the bitumen.

or google "Stucco" as beloved by the Georgians etc

Gypsum outside I would expect to be always damp and mouldy..

Jim K

Reply to
Jim K

Agreed (although crumbly, not mouldy).

Sand and cement render would be another option, and something which doesn't take as long to set (although still much slower than gypsum plaster).

Reply to
Andrew Gabriel

Black stuff is your damp proofing, probably bitumen paint. Not much will stick to it.

Screw cement panel boards to the surface. They will not rot, fungal mould or go to mush like plasterboard.

Reply to
js.b1

thinking on-- you could paint on a fresh coat of bitumen onto the bitumen, then another and on that 2nd coat whilst wet, throw loads of dry sharp sand at it, what sticks will give a key for render etc....

Jim K

Reply to
Jim K

HomeOwnersHub website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.