Cement render impossible to remove - options?

[sinead]

We have a house which was built circa 1760. A cement render was applied at some stage and when we renovated a few years ago, a conservation architect advised that the render was so tightly bonded, it would be impossible to remove without causing significant damage to underlying structure. We now have significant damp in two rooms and the cement render remains very well bonded, we had a hot lime specialist have a quick look today, he also feels that there is a real risk to the underlying stone if we proceed with remove as it was in his view, an exceptionally hard cement render. We need to go back to the architect but wonder if anyone else has had the same problem and if any solutions were found?

 

[a twig]

What is the stone underneath?

 

[sinead]

Not sure, architect report referred to stonework which may have been covered in a harling.

 

[a twig]

So in our case we had our stonework (bath stone ashlar) covered with a cement based slurry and nothing was shifting it.

We ended up mechanically spinning it all off and taking all the stone back 1/4 inch or so to get a new finish.

Not really an applicable approach for rubble stone walling though, hence my question

 

[fernicarry]

The guys who cut the cement pointing off of the front of my house last year said it was the hardest job they'd ever done. Took them about 10 weeks all up including re-pointing and repairs to the dressed sandstone.

It wasn't rendered but the cement was pretty liberally buttered over the stone. Its a rubble construction, referred to locally as whinstone. The stone is extremely hard, drilling into it is quite a task, but brittle so lots of chips came off with the cement. Seeing as how its rubble that didn't affect the end appearance and once repointed in lime it looks absolutely fantastic.

I guess the starting point for you would be to try a small section and see just how much damage is done getting the cement off of whatever is underneath. Our guys did a lot by hand but angle grinders were also enlisted to give them an edge to work against. This has left a few gouges in the stone which isn't ideal but ultimately its far more beneficial to get the cement off.

 

[CliffordPope]

"when we renovated a few years ago, a conservation architect advised that the render was so tightly bonded, it would be impossible to remove without causing significant damage to underlying structure. We now have significant damp in two rooms"

That reads as if there was a delay of a few years before the damp appeared?
What happened before then? I'm just wondering whether some other changes might have caused, or exacerbated, the damp.

 

[sinead]

At the time, a lime mortar was applied to the basement level (which had escaped the cement render), it was hoped this would help. The cement render was deemed impossible to remove, though we were aware that this may lead to interior damp - which it has, have had other distractions and now looking to address this now. Have been told by two specialist companies that removal is likely to cause significant damage - was hoping others may have had some sort of solution to similiar problem

 

[Zebra]

This "significant damp in two rooms," could it have another cause beside the render?

 

[CliffordPope]

This "significant damp in two rooms," could it have another cause beside the render?

That's what I was saying - the cement render has apparently been there for ages, but the OP says

"though we were aware that this may lead to interior damp - which it has," .

Surely if the cement render was responsible it would always have been damp, from the start, yet apparently it wasn't present when he became aware that it "may lead to damp".

 

[88v8]

Perhaps it was rendered shortly before the OP bought... if removing it damages the stone, unfortunate, but if it is then rendered in lime does that matter?

I would have it taken off, otherwise one will be forever worrying about the harm it is doing.

Ivor

 

[sinead]

Apologies for confusion, just to clarify, my husband grew up in this house, there was always damp problems. 15 years ago, we renovated it, at that stage the conservation architect felt that the render was not ideal but she felt it impossible to remove and that other options may address much if not all of the damp. Hence, new lime render at basement level, new chimney built etc. She clearly said the cement render was not good long term for house, told us the house may need to dry out. Most of the house dried out very well, but we have two separate spots of significant damp. Awaiting a return visit from architect but concerned that render removal may not be feasible due to previous concerns that removing it would damage stone.

 

[Zebra]

Ah, so the render didn't cause the damp. The damp was always there, and has dried elsewhere but not in these two places. So what else is going on in these places? High external ground levels? Other sources of penetrating damp? Poor air circulation internally? Cold bridging? ...?