Fake rough cast

[vicky whitworth]

Hello, one end of my rubble stone cottage is a horrid 1990s two storey, brick built extension painted in white sandtex. Don't blame me. I inherited it and ideally would pull it down and start again but my funds don't allow for that. It looks like a public convenience. I was thinking of rough casting the outside for the following reasons: cottages round here in Devon were rough cast; it would disguise the horrid modern cheap brick work; it would sit more comfortably alongside the limewashed rubble stone older parts of the cottage.
My question relates to how I might do this. I don't think there are any breathability issues as the extension is of modern cavity construction. Although I have left the sandtex to decay since we moved here four years ago plenty of it is still adhering and plenty is flaking. I don't want to have to get it all off. I would prefer to rough cast in lime as I think it will look softer and more in harmony but will I get it to stick to the sandtex? Is it not worth it and I might as well go for modern rough casting (what is that?). Is there some way I could get lime based rough casting to stick (bearing in mind that breathability isn't an issue? Any advice gratefully received. Thanks, Vicky

 

[JoceAndChris]

What an interesting question! I wish I knew the answer! (relevant for my own cottage too!)

 

[Roger H]

Insulate externally and render over the top of that. Lots of technical info and discussion on this issue at Green Building Forum.

 

[kevmiles1]

It is pretty straightforward to roughcast with lime, although if you want a really good finish I would recommmend a base coat first otherwise you will still see the pointing of the bricks through the roughcast.

NB There are a lot of roughcast cottages in devon but originally most would have been a smooth finish roughcast tends to be but not always a predominantly cement finish

 

[chuckey]

I would hack it off - I did this once on a 1930s semi, the paint was OK, but the undercoat was dropping off the scratch coat. In my case it was a relatively easy job though rather dusty.
If you intend to do it youself, have a try out to see how easily the old rubbish comes off. If it looks as though it is dificult, buy the cheapest SDS hammer drill with a hammer stop (<£50) and a wide chisel bit (£5?), these are ferocious beasts and will remove stuff at an astonishing rate - You will be spending more time moving the ladders then hacking.
Don't insulate the exterior, insulate the cavities with polystyrene beads before rough casting.
Frank

 

[hoppy]

but will I get it to stick to the sandtex? Thanks, Vicky

No...... you would need to either remove All the paint or fix EML over it first, then you can render till your hearts content...