Lime or Cement Render

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11 Aug 2011
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Location
Cumbria
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United Kingdom
Hi,

We are just finishing purchasing an old 1800s end terrace house with solid sandstone walls and are looking for some thoughts with regards to some external render work we are planning.

A bit about the house:
• The house has recently had an injected damp course which from what I have read is pointless as they rarely spread out enough to create a complete damp course on ½m thick old walls.
• Externally on all walls down to the floor there is a roughcast render coat which is in need of some repair, particularly the bottom foot.
• Around the base of the property is a 1m wide concrete path.
• There is no evidence of internal damp however, high moisture readings were recorded inside the property during a buildings survey. This was put down to a high external ground level.

After doing a lot of reading, I have been unable to work out what is on our external walls, whether it is lime roughcast or cement roughcast, is there any way of finding out other than having it sent off for analysis?

Our plans for renovating the external walls is to angle grind / dig out a ½ foot channel down 15-20cm in the cement path down to soil and fill with gravel to create an evaporation point . Then remove the lower 1 foot of render (as this is blown in quite a few places) and re-render in hydraulic lime mortar NHL3.5 and over paint in 4 coats of lime wash.

Our worry is if the house has been rendered at some point in rough cast cement will this be OK or are we better to simply patch render in cement or lime and paint with a good masonry paint (if cement). If lime I think we will need to look at stripping the existing masonry paint as there are quite a few layers, patching the wall with lime putty and lime washing .

We know in an ideal world the house should be lime rendered but if it is cement we want to avoid stripping off all the render and being subject to the BCO Thermal Element 24% rule as the remaining render is in relatively good condition and adding insulation to the wall internal or external would not be in keeping with the property or its surroundings.

Thanks for your thoughts guys.

Dave
 
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After doing a lot of reading, I have been unable to work out what is on our external walls, whether it is lime roughcast or cement roughcast, is there any way of finding out other than having it sent off for analysis?
Lime mortar is porous and cement isn't, so if you leave a chunk in water for a few hours, then take it out and break it, you can see if it's damp inside. I bet it's cement.

You're right to tackle the cement at the base of your walls, but if it's cement render then you really will have to take it all off somewhen... Walls need to breathe.

I presume your house isn't listed? That would give you a good argument to have with the BCO.
 
No sadly its not, the only thing I can think of is re-plastering the gypsum walls internally with Lime. This is as well as the evaporation point and lower lime external render.

While if more then 25% is going to be done it requires notification how they gonna know if its done adhoc by myself and its internal plaster? (there is no other advisable work going on).

Thanks for the advice with regard to water will give that a try I have got a feeling its cement as well. I wish the people in the past had known how bad cement was for these old buildings.

Dave
 
No sadly its not, the only thing I can think of is re-plastering the gypsum walls internally with Lime. This is as well as the evaporation point and lower lime external render.

While if more then 25% is going to be done it requires notification how they gonna know if its done adhoc by myself and its internal plaster? (there is no other advisable work going on).

Thanks for the advice with regard to water will give that a try I have got a feeling its cement as well. I wish the people in the past had known how bad cement was for these old buildings.

Dave

If I were you I would knock the lot off and start again using lime motar.

I live in a medieval cottage that has had some "plasterers" at it at some stage or other :rolleyes: Bonded walls, pva, the usual crap. The biggest mistake with "modern plasterers" is they don't understand the concept of a building that needs to breath, do anything to stop this and you will get no end of trouble, damp......

I stripped it all back and re plastered they way it was done 600 years ago. No damp.

Good luck
 
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I live in a medieval cottage that has had some "plasterers" at it at some stage or other :rolleyes: Bonded walls, pva, the usual crap. The biggest mistake with "modern plasterers" is they don't understand the concept of a building that needs to breath, do anything to stop this and you will get no end of trouble, damp......
Absolutely true, sadly.

I stripped it all back and re plastered they way it was done 600 years ago. No damp.
It's good to prove the principle works, isn't it? I did on my house - see http://houseintheenchantedforest.blogspot.com/ - I'm sat here in the dry and warm, but when I bought it last year it was cold, damp and would have fallen down soon!
 
Thanks for all your help guys its been excellent!! Will try test the render when we finally move in. and work from that will deff be creating a evaporation point and removing any gypsum in the house. I will keep you updated any external work is gonna have to wait till next spring now winter has deff set in in cumbria!! 70mph winds today!! + frost can't be far away.

BTW I have been using the 'old house handbook' an excellent book
 
I live in a medieval cottage that has had some "plasterers" at it at some stage or other :rolleyes: Bonded walls, pva, the usual crap. The biggest mistake with "modern plasterers" is they don't understand the concept of a building that needs to breath, do anything to stop this and you will get no end of trouble, damp......
Absolutely true, sadly.

I stripped it all back and re plastered they way it was done 600 years ago. No damp.
It's good to prove the principle works, isn't it? I did on my house - see http://houseintheenchantedforest.blogspot.com/ - I'm sat here in the dry and warm, but when I bought it last year it was cold, damp and would have fallen down soon!

I will dig around for some pictures of the house and some work that has been done for you to look at. But I will add that It's STILL a working project!! Three years into it as well!!! At the moment I am fighting to with the drainage. The cottage has no foundations and is built on clay. Over the years the place has been neglected and grounds work outside has messed up the natural flow of water (the area has large springs flowing all around, I have a fresh water spring outside the front door. So the water levels have risen aroung the house and was comming up the floor of the house in parts. I found the original drainage system to the house and have just cleaned it out, repaired the brickwork and connected it all up again and it's working nice, no more water!! The problem I have found is that I start a job that after all the prep has been done has uncovered some magor work that puts everything else back. Old houses hey?!?

 

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