Entire inside of old brick home covered in cement render. Fixable?

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maxi2024

New Member
Hi all,

Been lurking here as a guest for a while since I started having issues and gaining knowledge slowly about my case, so here goes:

I had an ignorant renderer slap about 6 metric tonnes of sand & cement render (w/ hydrated lime added) throughout my 1880s, brick & lime mortar home (interiors only). I didn't know there was such a thing as lime render and just spoke to the wrong people, as it turned out. Here in Australia, it's rare to find a renderer who understands breathability, movement etc. It's just, "you want sand n cement or acrylic mate?"

It has adhered spectacularly well, but there are big patches that are not drying out super well. Note: this is a terrace house and the below photo is an attached wall to a neighbouring dwelling.

Moisture meter showing up to 21% in places. Removing this render now will likely cause significant damage to the bricks underneath.

What's the best way to go from here?

The most educated advice I have received is the below:
1. Used the wrong lime in hydrated lime - should've used putty lime.
2. The sand & cement render will breathe, although it won't breathe well. With no water entering the walls, it should eventually dry out.
3. I can white set over the top of this as white set is breathable.
4. I should not paint the white set but instead use a lime wash that breathes.

How good does this advice sound in your opinion? Would you add anything? Dismiss anything?

Is there a way to fix this effectively?

Here's a pic underneath of the worst section (Note: this is an attached wall to another dwelling that has also cement render on the other side). Rendered 6 months ago and roof has been on for 1.5 months. Thanks in advance for your help on this!

Max

Entire inside of old brick home covered in cement render. Fixable?
 
maxi2024 said:
Hi all,

Been lurking here as a guest for a while since I started having issues and gaining knowledge slowly about my case, so here goes:

I had an ignorant renderer slap about 6 metric tonnes of sand & cement render (w/ hydrated lime added) throughout my 1880s, brick & lime mortar home (interiors only). I didn't know there was such a thing as lime render and just spoke to the wrong people, as it turned out. Here in Australia, it's rare to find a renderer who understands breathability, movement etc. It's just, "you want sand n cement or acrylic mate?"

It has adhered spectacularly well, but there are big patches that are not drying out super well. Note: this is a terrace house and the below photo is an attached wall to a neighbouring dwelling.

Moisture meter showing up to 21% in places. Removing this render now will likely cause significant damage to the bricks underneath.

What's the best way to go from here?

The most educated advice I have received is the below:
1. Used the wrong lime in hydrated lime - should've used putty lime.
2. The sand & cement render will breathe, although it won't breathe well. With no water entering the walls, it should eventually dry out.
3. I can white set over the top of this as white set is breathable.
4. I should not paint the white set but instead use a lime wash that breathes.

How good does this advice sound in your opinion? Would you add anything? Dismiss anything?

Is there a way to fix this effectively?

Here's a pic underneath of the worst section (Note: this is an attached wall to another dwelling that has also cement render on the other side). Rendered 6 months ago and roof has been on for 1.5 months. Thanks in advance for your help on this!

Max

View attachment 80255
Click to expand...


You need to find out the reason for it not drying out.

Has it been dry and then patches appeared?
Or just a really slow process?
 
getting the render off won't damage the bricks that much unless they coated it with a chemical/bonding agent first
I would try to get a small patch off and see how that goes.
If you you want it restored properly, all the render has to come off and possibly sand blasted to get rid of the bonding agent.
Then it should be rendered with earth/lime and lime render. Although a hot mixed limewash might be sufficient and more cost effective. Depending on the state of the joints, you might want to repoint it with lime mortar.

Another thing to consider is rising damp... I assume you don't have a damp course... in this case you need walls with an extremely performant drying capacity. The cement render reduced that capacity significantly, hence the problems.

You could also try running a dehumidifier for a month or so because maybe the wall is still damp from applying the cement render. If you can get your wall to dry out with a dehumidifier, see how your wall reacts after you power off the dehumidifier. Does the damp come back? If yes then you're most likely dealing with rising damp.

If it is rising damp, maybe installing a damp course might be more cost-effective than hacking off the cement. A proper damp course will last you 20-30 years.

In any case, I'm really sorry about your situation.

I think watching this video will help you better understand how the walls of your house were originally designed to work:


For now, don't make any hasty decisions. Try to analyse what is really going on with your wall and educate yourself best you can. Because unfortunately you cannot depend on most contractors to do the thinking for you these days. I don't blame them because there is a lot of contradictory and confusion information out there, even perpetuated by government policy and industrial marketeering. Inform yourself and try to find someone locally who has a better understanding of these things. Look for architects that design ecological buildings. You'll have more luck finding a competent contractor through people and companies like that.
 
Woods said:
getting the render off won't damage the bricks that much unless they coated it with a chemical/bonding agent first
I would try to get a small patch off and see how that goes.
If you you want it restored properly, all the render has to come off and possibly sand blasted to get rid of the bonding agent.
Then it should be rendered with earth/lime and lime render. Although a hot mixed limewash might be sufficient and more cost effective. Depending on the state of the joints, you might want to repoint it with lime mortar.

Another thing to consider is rising damp... I assume you don't have a damp course... in this case you need walls with an extremely performant drying capacity. The cement render reduced that capacity significantly, hence the problems.

You could also try running a dehumidifier for a month or so because maybe the wall is still damp from applying the cement render. If you can get your wall to dry out with a dehumidifier, see how your wall reacts after you power off the dehumidifier. Does the damp come back? If yes then you're most likely dealing with rising damp.

If it is rising damp, maybe installing a damp course might be more cost-effective than hacking off the cement. A proper damp course will last you 20-30 years.

In any case, I'm really sorry about your situation.

I think watching this video will help you better understand how the walls of your house were originally designed to work:


For now, don't make any hasty decisions. Try to analyse what is really going on with your wall and educate yourself best you can. Because unfortunately you cannot depend on most contractors to do the thinking for you these days. I don't blame them because there is a lot of contradictory and confusion information out there, even perpetuated by government policy and industrial marketeering. Inform yourself and try to find someone locally who has a better understanding of these things. Look for architects that design ecological buildings. You'll have more luck finding a competent contractor through people and companies like that.
Click to expand...

You recon the earths flat or round mate ? serious question !
 
Tha
Woods said:
getting the render off won't damage the bricks that much unless they coated it with a chemical/bonding agent first
I would try to get a small patch off and see how that goes.
If you you want it restored properly, all the render has to come off and possibly sand blasted to get rid of the bonding agent.
Then it should be rendered with earth/lime and lime render. Although a hot mixed limewash might be sufficient and more cost effective. Depending on the state of the joints, you might want to repoint it with lime mortar.

Another thing to consider is rising damp... I assume you don't have a damp course... in this case you need walls with an extremely performant drying capacity. The cement render reduced that capacity significantly, hence the problems.

You could also try running a dehumidifier for a month or so because maybe the wall is still damp from applying the cement render. If you can get your wall to dry out with a dehumidifier, see how your wall reacts after you power off the dehumidifier. Does the damp come back? If yes then you're most likely dealing with rising damp.

If it is rising damp, maybe installing a damp course might be more cost-effective than hacking off the cement. A proper damp course will last you 20-30 years.

In any case, I'm really sorry about your situation.

I think watching this video will help you better understand how the walls of your house were originally designed to work:


For now, don't make any hasty decisions. Try to analyse what is really going on with your wall and educate yourself best you can. Because unfortunately you cannot depend on most contractors to do the thinking for you these days. I don't blame them because there is a lot of contradictory and confusion information out there, even perpetuated by government policy and industrial marketeering. Inform yourself and try to find someone locally who has a better understanding of these things. Look for architects that design ecological buildings. You'll have more luck finding a competent contractor through people and companies like that.
Click to expand...

Thank you so much for this detailed advice. Even now, snake oil salesmen are everywhere trying to sell me injection products to fix it quickly. I'm going to take it slow, do as much research as I can and educate myself. Thanks again, so much!
 
maxi2024 said:
Tha

Thank you so much for this detailed advice. Even now, snake oil salesmen are everywhere trying to sell me injection products to fix it quickly. I'm going to take it slow, do as much research as I can and educate myself. Thanks again, so much!
Click to expand...
you're welcome. Unfortunately no amount of injections would help because your cement render acts like a giant plug to keep water in the wall. The convective drying capacity of the wall relative to the amount of moisture your wall absorbs in your particular case has to be high enough to get rid of the moisture. Pure and very feeble hydraulic lime mortars maximise this potential while hydraulic lime (aka cement) minimises it.

Here is an interesting little video of an I****n temple case study that had the same problems with cement repairs:

And there's so many more examples and proof of the negative effects of cement in above ground building fabric.

If the moisture in your wall is from rising damp, perhaps a damp course might be enough. But in the long run, that cement render will dramatically increase the deterioration of the masonry. If I were in your situation, the choice would be easy, though painful. But if this building is worth it to you and if you want to increase its longevity (and promote the health of yourself and your family), I personally think it's worth it: hack it all off and go with a fat lime render in stead. The difference will be staggering.

But first make sure that you figure out where the moisture comes from; verify that there's no leaks and try to figure out if there is rising damp and to what extent, if any.

I know it sucks to undo work you already paid for... but look at the people in the video: they got rid of the concrete as well... if the building is worth it, then you gotta do it.

The superiority of fat lime has been proven throughout the ages. It wasn't until the 50's when portland cement completely took over. We've lost this valuable traditional knowledge and I consider it one of the primary fallacies of modern building practices.

If you want to research this further, there is someone who wrote an excellent book on this, comparing case studies to historic text to figure out how things were done traditionally and why these traditional methods perform so much better:

Entire inside of old brick home covered in cement render. Fixable?
 
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