Permacoat spray on coating - advice on removal

[Bitstreams]

Hello..

Our stone cottage (c1850 we think) has been vandalised with one of those spray on coatings that looks a bit like painted pebbledash but feels like plastic. It's not faired well and the cracks in it have let in water that then gets trapped at the base of the walls.
In some places you can peel it off with your hands, in others (especially where there's brick in-fill) it's adhered like paint. Beneath it there is a couple of mm of grey render? this is slightly glossy and quite brittle. The walls themselves are mid brown to cream stone, some blocks and some rocks - if you see what I mean.

I've started to get the stuff off but only with mixed results. It comes off beautifully in some sections, all the way back to the stone - but in others it's welded to the walls.
What should I be using to get rid of it? Options seem to be:

1) Cold chisel and a hammer. This does mark the wall unless I'm very carefull. Also, I have all of a 4 bed detached cottage to do.
2) Grit blasting - ideally I'd want to do the work myself - does this rule this out as an option
3) Chemical paint stripper
4) Eco paint stripper (such as homestrip)
5) SDS drill (or Boschbreaker) - I did use this a bit at the base of the wall but am worried about damaging the stone.

Any advice very gratefully received as we're running out of good weather (well not winter weather) and I really want to make some progress on this. I think I've attached a picture of the wall as well.

Simon

 

[Moo]

It's unlikely that you could get it off by chipping or abrading without doing some real damage to the stone beneath. Chemical stripping is by far the safest (and most efficient) way to tackle the problem, and your best bet is to get in touch with Strippers of Sudbury http://www.stripperspaintremovers.com/index.htm .... If you can send them a sample of the coating, they will then be able to recommend the appropriate product.

 

[chuckey]

I have a builder friend who hired a proper grit blasting kit. Diesel powered, 4000 psi, the grit it used, "exploded" on contact with the cement render he was removing, so lots and lots of very fine dust. He had to wear a complete goon suit and respirator, all windows and doors had to be covered with shuttering ply else the glass got etched as well. Used a lot of grit (in two weeks time I could ask him his grit useage and the area). I have used a baby version - 140 psi air compressor and a de-rusting spot gun to clean interior walls. The kit and grit cost about £25 for 2 days hire. I would hire the baby version and see if its any good for your application. One advantage I had was that I could sweep up the grit and re-use it - a bit difficult if you are on the top of scaffolding? However if it works, then to buy the lot, less then £200 + grit as used/recycled.
I think your real problem is the render, a thin chisel made from a power hacksaw blade, might get behind it to lever bits of the wall. Does doing this damage the block too much? If it just pull the surface off, say 2mm, then as the block thickness is 150mm+, I would think you could live with that. Else do what SPAB says :- leave it alone, it'll look awful, but you won't be inflicting any more pain on the building.
Frank

 

[DaveBrigg]

Consider what finish you want at the end. If you will be replacing what sounds like cement render with lime, superficial marking of the stone by a hammerdrill may be acceptable since it will not make a difference structurally, and will soon be unseen. Moo's suggestion of a chemical stripper is great, but having gone to the effort and expense, will you still be left with the problem of how to remove the render? Using an SDS drill, I managed to remove the cement from my house without too much more damage, but that was brick, which gave a fairly flat surface to guide the chisel. More damage was caused by the cement render being stuck so firmly in places that it pulled away the surface of the bricks as it came off. Whatever you decide, it does not look like a particularly easy job, but if your cottage is over 150 years old, not getting the job finished until next year may not be such a big deal.

 

[Moo]

Dave - it seems as though the problem isn't cement render, but a sort of paint finish, which is why I suggested going down the Strippers route.
We had a house that had been painted since the 1920s, and soon realised that the latest coat of emulsion paint was doing the bricks a heap of no good (trapped moisture, in the main). We tried water-jet and fine grit-blasting on a couple of inconspicuous areas but they both took the surface of the brick off. Strippers came along and worked their magic and it was as though the brick had never been painted. Wonderful.
Unfortunately, doing the whole (largish) house was way beyond our means at the time, and we have since moved, but getting rid of that emulsion paint is still at the top of my When I Win The Lottery list.

 

[Bitstreams]

Hello,

thanks for all the replies so far. I've emailed Strippers for advice but also tried a textured paint stripper (really designed to remove Artex) with a little success. The textured coating does come off, but most of the time it's leaving behind a very thin (1mm) hard surface. This is quite brittle - if you hit it at 90 deg with a chisel it pops right off, but you can only clear about a square cm at a time this way. If you try and get behind it you mark the stone (which is a sandstone I think and pretty soft). I'm not sure what the hard durface is - in colour and texture it's a bit like the face of a knapped flint - mottled grey and brown.

More suggestions welcome

Simon

 

[Bitstreams]

just posting a follow-up. Amazingly it's nearly two years since I posted the original question.

We tried so many things to get this horrible coating off the walls. We investigated grit/sand blasting and we tried chemical stripping (which only succeeded in removing the texture and not the plastic and scared us silly). In the end we have used a combination of an SDS drill to remove the larger concrete render/pointing and a lump hammer and cold chisel. We then repointed in lime and have nearly finished lime washing one wall.

View attachment 1

Slightly emboldened we're now starting on the back of the house ..

Simon

 

[MdB]

Looks good to me!

 

[Feltwell]

Your finished section looks really good. I like the two-colour approach on your windows as well.

 

[Moneypit]

Maybe too late for you to try if you have found a technique you are happy with, but I have had some success with burning coatings off with a decent size torch. You can get propane torches that have large nozzles fed by hose from decent size bottles, often used as weedburners. In my case I have had to work quickly, scraping the paint off while still softened by the heat. It doesn't work well if you actually burn it because that chars it and it is still difficult to remove. I have tried a variety of scraping tools, long handled being the best to keep from heating your hand (even when gloved) from getting too hot. Best tool so far has been a stainless steel barbecue slice from Aldi !

One other safety tip is to not let the heat build up in the stone or render too much as you can cause the surface of it to explode either from air pockets or trapped moisture turning to steam

 

[Delta]

Well done, good job so far.

I've heard a needle gin be recommended for similar jobs, not sure if you considered it.

 

[Bitstreams]

I'm planning to hire a needle gun and try that, as there's still lots to do and we're running out of summer.

Barge boards went up yesterday which has tidied things up a bit.

 

[Bitstreams]

Well for anyone with the same horrible coating to get rid of, the needle gun was successful if a bit slow (and very noisy).

We have much much more to do but today I finished the last coat of limewash on the back of the house and the windows are almost done. With any luck I should be able to get the scaffolding tower down tomorrow.




The untouched corner is where a door used to be and we're opening it up as an additional window, and no it won't be a plastic one. We'll replace that once we've replaced all the rotten ones (and saved up a bit more).

Simon