Cement Render + Waterproofer + Sharp Sand = Basement Wall

[SparrowHawk99]

Hi everyone,

Just wanted to get a heads up on what I have planned for this basement wall.

The wall in the picture is a party wall not an earth retaining wall, in fact despite having a basement none of the walls are earth retaining. The earth is retained in the garden with another wall.

Now I am intending to use cement, sika waterproofer and sharp sand and render this wall. I then intend to paint on something called a cementone aquaprufe, which is a cold applied bitumen to the wall, and then finally dot and dab standard 12.5mm plasterboard to the wall, and then skim with finishing plaster.

My question is, is there a maximum thickness I should not exceed when I render with the cement? Will I get cracking? The front section of the basement had been rendered by the previous owners and is 20mm.

There is an opening for the fireplace which I will fix 12.5mm board to and a vent to allow for ventilation. The concrete floor has a DPM in it fortunately.

I just want to make sure I'm doing the right thing if I can have some opinions from you chaps? Thanks

P.S I am going to take more of the lime off the wall before I start because there is still quite a bit on there and may take the ceiling off where it abuts the wall. That pink stuff at the top is the old lime render with horrible pink decorating scheme

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• SparrowHawk99
• 2 Oct 2013
• 1

 

[barnettgs]

The wall looks dry, why would you want to waterproof it? If you do that plus cement rendering, it will simply trap moisture in the wall and can cause the damp. The lime is there for a reason, to make the wall breathable and let moisture out of the wall.

Have a read at: http://www.heritage-house.org/pages/managing-damp-in-old-buildings.html

 

[SparrowHawk99]

Barnett thanks, I agree with you and decided to take all the stuff I've bought back and go with the lime option

 

[barnettgs]

Glad to be of a help. I have just come across this site last week when I was looking for a solution for a small section of damp wall that had been stripped off and re-plastered. It turned out to be the problem was to do with the cement render outside.

Also our kitchen extension has very bad damp problem for years and it was caused by cement rendering after a major renovation in 1985.

 

[SparrowHawk99]

Well it's a bit of a relief not having to do the work lol, but there's now the problem of finding someone that can lime render. Have you done it yourself? I'm no expert in rendering. Just had a look at a youtube how-to video of two guys lime rendering and then lime plastering a wall and it looked pretty skilled. I'm going to contact a few builders tomorrow but I have a feeling it won't be cheap!!

 

[barnettgs]

I am no expert too but I plan to cut out the thick rendering on the bottom round the back of the house and kitchen to let them dry out first and then I might give it a try to do the lime rendering myself or find a local man who knows how to do it.

At least, nothing is worse than damp-proof and plaster the wall only to find the damp appearing on it later! My house had damp proofed nearly 30 years ago and it doesn't help a bit but along with cement rendering, my kitchen has very bad damp problems which it didn't have before the house was being renovationed and damp-proofed!

 

[NickB_99]

Glad to be of a help. I have just come across this site last week when I was looking for a solution for a small section of damp wall that had been stripped off and re-plastered. It turned out to be the problem was to do with the cement render outside.

Also our kitchen extension has very bad damp problem for years and it was caused by cement rendering after a major renovation in 1985.

It is a useful link that you posted. If you get some time, would encourage you to post it onto the Wiki at the top of the plastering forum.

 

[SparrowHawk99]

I am no expert too but I plan to cut out the thick rendering on the bottom round the back of the house and kitchen to let them dry out first and then I might give it a try to do the lime rendering myself or find a local man who knows how to do it.

At least, nothing is worse than damp-proof and plaster the wall only to find the damp appearing on it later! My house had damp proofed nearly 30 years ago and it doesn't help a bit but along with cement rendering, my kitchen has very bad damp problems which it didn't have before the house was being renovationed and damp-proofed!

I was thinking the same. Was thinking about applying two scratch coats (I think they are called) and then perhaps leaving the final finishing coat to the expert. They sell hydraulic lime at my local merchants, but not entirely sure this is the stuff to use?

 

[barnettgs]

Yes you can use that - see the link: http://www.heritage-house.org/pages/lime-plastering-and-rendering.html

Also worth googling about plastering with this material.

 

[barnettgs]

It is a useful link that you posted. If you get some time, would encourage you to post it onto the Wiki at the top of the plastering forum.

Just added a couple of links onto the Wiki so check and see if it's ok? Thanks

 

[NickB_99]

Just added a couple of links onto the Wiki so check and see if it's ok? Thanks

Looks good to me. Nice one.

 

[SparrowHawk99]

Keep us updated with progress pics Barnett, depending on how you find it I might decide to attempt it myself as well

 

[barnettgs]

Keep us updated with progress pics Barnett, depending on how you find it I might decide to attempt it myself as well

Sure, I could do that. I have done that in very small area to check out the condition of the wall, with hammer and chisel and the stone is visible wet and quite soft but it was so tough to chisel out the cement render which is very thick, at least 2 or 3cm! It is still too small to take a picture of.

So I may need to hire a chisel hammer tool for a day or two to take off. I plan to do that on the rear of the house and around the kitchen extension. The rest of the house seems ok but first I will see how the condition of the wall is.

In the meanwhile, someone is doing a major job with stripping off the cement render - along with other wall and windows repairs etc and it is quite a long process - you can read it at: http://oldlawnsrenovate.blogspot.co.uk/2012/10/what-lies-beneath.html

 

[SparrowHawk99]

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• SparrowHawk99
• 4 Oct 2013
• 1

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Can I make a suggestion?

I use a SDS hammer drill + flat head chisel which you can buy cheaply in screwfix.

All the render you see taken off my walls here was 20mm thick. The key is to get in behind with the flat head chisel and drill along the wall not into it. Some of the time the cement cracks and drops off in large chunks. Other time I had to work away at tiny pieces at the time, the bottom of the walls seems to be most difficult - I'm assuming perhaps the cement had some sort of weatherproofer in it already, who knows

I can see where the brown, original lime is saturated with water and where there's clearly black/dark damp patches at the bottom where the waters not been allowed to escape!!!

Next thing is to carry on around and under the staircase!! Some of the highest damp meter readings are in this area so I want to get it off ASAP

Need to get the trickle vents into the windows ASAP also, been meaning to do this for ages

That guy with the farm did it all with a lump hammer and chisel !!! My hands blistered up from doing that after about 2 or 3m3 !!!

 

[barnettgs]

Thanks for the suggestion but could I ask you what is SDS? I have a Worx main hammer drill if it's any use for chisel job?

Did you do that job today? My windows does not have small vent but I left the handles of small frame of windows a bit loose to let a trickle of air in. It did made a difference thoughout the house.