Removing cement render

[Hobden]

We're looking at buying an old cob house that has, unfortunately, been rendered with a cement-based render. Our surveyor says this is not good, and it really ought to be lime-rendered.

Does anybody know how easy it is to remove such a render? A big flat chisel and have at it? Or is this likely to damage the underlying cob?

H

 

[Zebra]

I don't know about cob, but I removed cement render from my entire house. I comb chisel is good, although might scar what's underneath so only to be used sparingly. An old wood chisel can be good - obviously it will blunt itself and you wouldn't keep it as sharp as you would for wood, but it can work for really stubborn sections. But the obvious choice is a masonry bolster. I wouldn't bother with a club hammer, you'll be tap tap tapping rather than taking a swing at it, so it'd be too hard on the wrists. I'd use a claw hammer.
Another possibility IF you don't damage the surface underneath, is to cut it into sections with an angle grinder with a diamond blade. Where I was taking off cement render from lath and plaster, this was helpful, it may not be in your circumstances. You'd have to go very carefully.
As for damage to the underlying surface, I don't really know about cob, but the only way to find out is to have a go. It would probably do less damage in the long term than leaving it on. Maybe tap around to see if there's a bit that sounds hollow and sort of "wants" to come off. Perhaps somewhere inconspicuous where you could repair it if you decided to abort mission. And make a start. Eventually you'll get to a point where you're committed and have to carry on!
I don't know from your post whether you would be up for doing it yourself. To be honest it isn't a job I'd trust a contractor with, they might be a little more heavy-handed than I would myself.

 

[JoceAndChris]

In contrast to Zebra' s valiant efforts, we paid a team of conservators who usually only work on G1 buildings and national treasures. I wouldn't trust just anyone either. I was interested to see how they'd get it off as it was concrete and in places 3 inches thick. It was very very stuck on to the underlying stone and they had to use SDS drills to get it off. In places ( corners) the house emerged rather damaged, but they were able to repair and make good. I'll upload a couple piccies to show you the during and the lime plaster after.
The whole thing took about 8 weeks and cost £25,000 for a team of three men.
Cob can be fragile ( as can any underlying structure) and I would carefully trial a section to see how it all behaves. I trialled a section got terrified and got the conservators in.

Hope that gives you an idea of how smart in looks in lime render and how the underlying damage gets repaired and is unseen. If you would like the details of the conservators PM me.

I didn't know how house would need such repair at the time of purchase, but I don't regret a single thing, it's worth the effort - so I would always advise buying the old house you've fallen in love with and sorting it out!

 

[88v8]

Where?

Yes, cement bad.

This could become a wallet-emptying example of mission creep. Are these people nearby?
http://www.cobcourses.com/cob-houses/

Go talk.

Ivor

 

[Hobden]

Thanks for the replies chaps.

The house is in Devon, and yes, JoceAndChris, we have fallen in love with it, so your final paragraph is music to my ears. My other half, on the other hand, is being a little more hard-headed about things. £25,000 seems not too bad for them taking the cement off and then replastering - any idea how much they charged you per square metre? My other half is thinking of hens too

Zebra - my initial thoughts were to do the getting-it-off side of things myself as I always argue that dismantling is easy, it's the putting back together that's hard. And I know from past experience that I'm not destined to be a plasterer! Even outside. Good suggestion about starting cautiously and out of sight somewhere. I might have to let them do the gable ends as that's probably higher up than I'd care to be.

88v8 - yes, we're expecting a money-pit, but the alternative is a 80s box or something and we really don't fancy that! What price beauty, eh?


H

 

[JoceAndChris]

There's nothing as rewarding and stimulating as an old house project. I'm glad you feel that way too and wish you all the luck with your purchase.
We're 8 years into our project and about 100,000 has been spent on it over that time. It needs another 100,000 which it isn't going to get! The biggie was the Swithland slate roof and re rendering of the chimneys which cost £50,000 this summer.
Today we're working on the new bathroom which has to be DIY as we simply have no budget now for more tradesmen. In the 8 years our skill sets have vastly grown and we now do all the plumbing, wiring, carpentry, decorating, tree surgery and wood harvest. None of it is really as difficult as the ordinary day job and it's amazing how skills and confidence grow!

I'm not sure about the price per square metre - the house has a west side that's 14m x 2.75m and an east side the same. Then there is a south facing bay that's 6m by 2.75. The north facing side we left in cement for various complex reasons.

The chopping off is much much much cheaper than the re plastering. My plaster was very expensive as I had one of the best plasterers in the country, he's won a lot of historic awards, and it was lined out work ( scored to resemble ashlar blocks). I agree for all that 25,000 wasn't bad! That includes 4 coats of limewashing as well!

When you think of what you can afford and what the old house needs it is very daunting but when you spread that over 20 years it's ok. Good luck!

 

[Hobden]

Your house is certainly looking very nice. I like the tag over the door too - did that mirror what was there before? We might have to have one now, though it'll probably be a tad less erudite, "eat, drink and be merry" maybe, though I guess that's not a million miles from yours If we get the place we want then I might be in touch in the future, thanks.

H

 

[JoceAndChris]

Good luck and I hope you get it! Yes eat drink and be merry is much like Live grow flourish! We spent ages and ages mulling over what to have! There wasn't anything there before and I decidedif future owners dislike it they can just chop off and replaster.