Cement pointing problem?

[Tman10]

Another new member with what seems to be a perennial problem. So we’ve bought a Victorian sandstone house in Cumbria, the survey did ‘touch’ on the pointing on the gable end, but not in any detail. Over the past two years however, as we’ve been living in, and working on the house as and when time permits, we’ve noticed some damp and mould problems. First I put it down to inadequate heating and condensation; the last owner had a 45yr old Rayburn with a heat output equivalent to a hairdryer, and laughably pathetic radiators; fadt forward and Rayburn is replaced with beefier oil cooker with PJ burners and proper radiators, and we have heat, yay! Problem remains, boo! Having now had a a number of tradesmen around and I have a plethora of diagnoses as to what the problem is, but basically it’s one of two: 1. Lack of insulation, nothing to do with cement pointing, and anyone that says otherwise is basically an evangelical lunatic. 2. It’s the cement pointing and anyone that says otherwise is basically a Neanderthal.
Doing my own research I’m leaning to option 2, minus the judgments. But now I’m in another position: how to deal with it. Everyone I’ve spoken with is booked up for year/s, and had told me I need to pull out the cement pointing ASAP. This seems easier said than done as the pointing is no more than ten years old and rock solid, also it is very liberally applied in places, and this is a very large gable end wall. The damp seems to be most evident in top floor bedroom and rear first floor bedroom (oddly enough front bedroom and living rooms seem fine). Does anyone have any recommendations or suggestions as to how we can most effectively and economically address the problem?

 

[aockenden]

A couple thoughts: it’s a bit suspicious that the dampest rooms in the house are NOT on the ground floor. This might indicate some other root cause besides the cement. Are there chimneys above these damp areas? Are there bathrooms nearby internally? Can we see pics of the internal damp spots? Definitely need more info.

 

[Toby Newell]

Hi, as Aockenden says no ground floor damp indicates maybe weather exposure and / or guttering issue. Although there is algae growth at the lower elevations. That looks like beautiful sandstone, which is as porous as a sponge so I don't think the main issue with the cement mortar is water retention, rather that it is destroying the sandstone (generally you want softer mortar than your bricks / flags so that it spalls preferentially, like a mechanical version of galvanic protection)

What is the inside rendered with? You want that to be lime plaster. I think the probability of you removing the cement without damaging the sandstone is zero, not sure many companies would take that on, they are already badly eroded. It would be a monumental task. I would look at guttering and interior plaster, I am not sure interior insulation would help unless it is breathable hempcrete (ask Aockenden about that) as you don't want to reduce the permeability that much.

What is your floor? A limecrete install might help.

Let's just get one thing straight, cement mortar on such a weathered sandstone is utterly tragically BAD, wrong, ignorant, dumb, full stop. Whether that is the cause of the damp issue is up for debate.

Adding non breathable insulation would also, possibly, be deleterious, but breathable insulation might help, as would a free draining, breathable limecrete slab.

I think all the guys are 'booked up for years' and your place on their queue would never advance, it would be a horrendous job. Possibly better to tackle it yourself, it would be cheaper to buy the tools and do bit bu bit, it would be a massive job. Such a shame people are that stupid, you would of thought contractors living and working in Cumbria might of come accross sandstone before and that some old boy down the pub might have told them not to use cement mortar.

 

[Toby Newell]

The flags are very weathered on that elevation, lots of lichen and algae, is it S, W or SW facing? Also the spalling looks very bad which indicates it might have been cement pointed before, eroded then cement pointed over the erosion, you know, just to speed it up.

 

[housewinnie]

Have you tried to chip away any yourself. A massive job I know but try a small area at a time. Sometimes it’s not actually applied that deep.

 

[housewinnie]

Not ideal but could coating it in lime wash help with the erosion and damp

 

[Tman10]

Hi, as Aockenden says no ground floor damp indicates maybe weather exposure and / or guttering issue. Although there is algae growth at the lower elevations. That looks like beautiful sandstone, which is as porous as a sponge so I don't think the main issue with the cement mortar is water retention, rather that it is destroying the sandstone (generally you want softer mortar than your bricks / flags so that it spalls preferentially, like a mechanical version of galvanic protection)

What is the inside rendered with? You want that to be lime plaster. I think the probability of you removing the cement without damaging the sandstone is zero, not sure many companies would take that on, they are already badly eroded. It would be a monumental task. I would look at guttering and interior plaster, I am not sure interior insulation would help unless it is breathable hempcrete (ask Aockenden about that) as you don't want to reduce the permeability that much.

What is your floor? A limecrete install might help.

Let's just get one thing straight, cement mortar on such a weathered sandstone is utterly tragically BAD, wrong, ignorant, dumb, full stop. Whether that is the cause of the damp issue is up for debate.

Adding non breathable insulation would also, possibly, be deleterious, but breathable insulation might help, as would a free draining, breathable limecrete slab.

I think all the guys are 'booked up for years' and your place on their queue would never advance, it would be a horrendous job. Possibly better to tackle it yourself, it would be cheaper to buy the tools and do bit bu bit, it would be a massive job. Such a shame people are that stupid, you would of thought contractors living and working in Cumbria might of come accross sandstone before and that some old boy down the pub might have told them not to use cement mortar.

Many thanks everyone for all the useful information, much appreciated .

Inside is original plaster as far as I can see, the worst spot is in the loft bedroom where previous owners have actually papered the walls with that laminated stuff (foil, bitumen, paper), doesn’t achieve anything other than to trap moisture, and any condensation actually sits on the surface of the bitumen where it’s exposed. Up in the attic it’s not much more reassuring.


The pointing in here is very soft and damp, all a bit of a mess.

Outside the gable end is adjoined by a concrete alleyway, this serves to prevent water escaping and I think can only serve to make the situation worse; it’s my plane to get that broken up and lifted, replacing with gravel.

 

[aockenden]

Many thanks everyone for all the useful information, much appreciated .

Inside is original plaster as far as I can see, the worst spot is in the loft bedroom where previous owners have actually papered the walls with that laminated stuff (foil, bitumen, paper), doesn’t achieve anything other than to trap moisture, and any condensation actually sits on the surface of the bitumen where it’s exposed. Up in the attic it’s not much more reassuring.
View attachment 12344
View attachment 12345
The pointing in here is very soft and damp, all a bit of a mess.

Outside the gable end is adjoined by a concrete alleyway, this serves to prevent water escaping and I think can only serve to make the situation worse; it’s my plane to get that broken up and lifted, replacing with gravel.
View attachment 12346
View attachment 12347

Don’t get me wrong, I absolutely agree with Toby and yourself that the cement is a completely inappropriate material, made all the worse when it’s used to point or render soft sandstone like yours. Definitely a recipe for spalling damage to the beautiful stonework as Toby says.

Obviously the tar / foil paper crap you mentioned is completely inappropriate as well and should be stripped off back to bare original masonry.

The pointing you’ve photographed and commented about being soft is not actually a problem, in fact it’s a good thing. That softness is in total contrast to the hard impervious cement pointing you’re worried about. Now just need to find out why it’s damp!

The fact that the two areas of damp you’re calling out in this post are in the loft and attic again would lead me to believe this issue is not directly caused by cement pointing and therefore wouldn’t be properly resolved by repointing in lime (though it’s a good idea anyways).

So are both the “loft” and “attic” directly under the roof? If either one is directly under your roof I would first be trying to rule-out a roofing or gutter leak. Next time you get a big rain you could sit in those rooms and look for water running down the damp walls. And might as well visually inspect the external roof, gutters and eaves condition around the damp areas ASAP to see if there’s any obvious repair needed near those internal damp zones. Other things to look for especially in the unfinished attic(?) would be like broken or detached extractor fan pipes that might be venting directly into the attic space.

If you thoroughly rule out those things then I’d be looking at the ventilation into the attic space under the assumption it’s actually warm moist air rising up from the house below and then condensing on the cold masonry without sufficient ventilation to dry it back out.

 

[Tman10]

Don’t get me wrong, I absolutely agree with Toby and yourself that the cement is a completely inappropriate material, made all the worse when it’s used to point or render soft sandstone like yours. Definitely a recipe for spalling damage to the beautiful stonework as Toby says.

Obviously the tar / foil paper crap you mentioned is completely inappropriate as well and should be stripped off back to bare original masonry.

The pointing you’ve photographed and commented about being soft is not actually a problem, in fact it’s a good thing. That softness is in total contrast to the hard impervious cement pointing you’re worried about. Now just need to find out why it’s damp!

The fact that the two areas of damp you’re calling out in this post are in the loft and attic again would lead me to believe this issue is not directly caused by cement pointing and therefore wouldn’t be properly resolved by repointing in lime (though it’s a good idea anyways).

So are both the “loft” and “attic” directly under the roof? If either one is directly under your roof I would first be trying to rule-out a roofing or gutter leak. Next time you get a big rain you could sit in those rooms and look for water running down the damp walls. And might as well visually inspect the external roof, gutters and eaves condition around the damp areas ASAP to see if there’s any obvious repair needed near those internal damp zones. Other things to look for especially in the unfinished attic(?) would be like broken or detached extractor fan pipes that might be venting directly into the attic space.

If you thoroughly rule out those things then I’d be looking at the ventilation into the attic space under the assumption it’s actually warm moist air rising up from the house below and then condensing on the cold masonry without sufficient ventilation to dry it back out.

That is really a very helpful response, and I thoroughly appreciate you taking the time to provide such a detailed and thorough response to my last post. I’ve had similar feedback to my questions posed on the situation in the attic by a local builder/stonemason and I was also wondering if I just managed to remove and re-point the lower 1.8 m also of the cement, pointing, and then limewashed as another poster has mentioned Would this be overall a reasonable solution to the gable end problem?

 

[aockenden]

That is really a very helpful response, and I thoroughly appreciate you taking the time to provide such a detailed and thorough response to my last post. I’ve had similar feedback to my questions posed on the situation in the attic by a local builder/stonemason and I was also wondering if I just managed to remove and re-point the lower 1.8 m also of the cement, pointing, and then limewashed as another poster has mentioned Would this be overall a reasonable solution to the gable end problem?

As I’ve already stated I think you need to do a thorough investigation to find out WHY your walls are wet to begin with (aka, where this moisture is originating from) BEFORE attempting any major remediation work. My previous posts explain steps you can take to begin narrowing down the possible underlying causes. Don’t prescribe a medication before you’ve diagnosed the underlying disease. Shooting blindly rarely hits the mark. Good luck!

 

[housewinnie]

Go slow. Strip and clean up all that bitumen and rubbish out from the loft and see if it all starts drying. It could be that it is starting in the loft and working it’s way down.

 

[Toby Newell]

Agree with Aockenden, easiest early remedy is remove all impervious coatings and increase ventillation, you have already sorted the heating.

Viewing roof and gutters in downpours can be very instructive. Your roof timbers look damp, it is very likely you have an issue up there seeing as that is the most damp.

However. I see moss and algae growth everywhere at low elevations meaning your flags are constantly damp.

As I said, despite cement being a totally incorrect medium for pointing your red Cumbrian sandstone flags, and despite there being a massive amount of cement by volume, the flags are, by their very nature, incredibly porous.

Therefore I don't think exterior permeability is your biggest problem. Removing the cement is a labour of love and should be done to slow the serious spalling issue you have but not necessarily for your damp issue.

Remove all impervious interior coatings, check roof, check gutters, consider a PIV system, these are the quickest and cheapest options.

Longer term lowering any ground levels can help, as could digging up the ground slab and installing free draining limecrete.

You obviously have rising damp as well as a higher problem.

I really don't think the cement mortar is the main damp culprit, it doesnt help but I would concentrate elsewhere.

Is your house exposed? A waterproofing compound like a silicone can sometimes help, this is breathable but very hydrophobic.

 

[Tman10]

Many thanks guys. I really appreciate your help and I will report back as and when I get further down to the root of the problem.

 

[Tman10]

Agree with Aockenden, easiest early remedy is remove all impervious coatings and increase ventillation, you have already sorted the heating.

Viewing roof and gutters in downpours can be very instructive. Your roof timbers look damp, it is very likely you have an issue up there seeing as that is the most damp.

However. I see moss and algae growth everywhere at low elevations meaning your flags are constantly damp.

As I said, despite cement being a totally incorrect medium for pointing your red Cumbrian sandstone flags, and despite there being a massive amount of cement by volume, the flags are, by their very nature, incredibly porous.

Therefore I don't think exterior permeability is your biggest problem. Removing the cement is a labour of love and should be done to slow the serious spalling issue you have but not necessarily for your damp issue.

Remove all impervious interior coatings, check roof, check gutters, consider a PIV system, these are the quickest and cheapest options.

Longer term lowering any ground levels can help, as could digging up the ground slab and installing free draining limecrete.

You obviously have rising damp as well as a higher problem.

I really don't think the cement mortar is the main damp culprit, it doesnt help but I would concentrate elsewhere.

Is your house exposed? A waterproofing compound like a silicone can sometimes help, this is breathable but very hydrophobic.

There has been work done on the roof, I recollect from the survey we had done, but I’ll need to dig further to understand exactly what. I think I’ll need to attack this from two points: the path and the roof; the pointing will I expect, be a more gradual process.

 

[Toby Newell]

Yes. Higher rooms more damp ergo there is local issue there. Moss and algae at lower elevations so there is also a lesser damp issue there. Start at the top. I really think the cement is a red herring, you have other issues.

 

[Tman10]

Yes. Higher rooms more damp ergo there is local issue there. Moss and algae at lower elevations so there is also a lesser damp issue there. Start at the top. I really think the cement is a red herring, you have other issues.

If that is the case then I shall be more than happy, dealing with the path and possible roof leaks, and ventilation issues sounds like a much easier problem than dealing with the cement pointing!

 

[alexander]

I notice from your pictures of the loft the timbers look rather damp, you could have an issue with condensation in the loft tracking into your stonework, the cement pointing in the stonework will trap the water ingress in the stone creating dampness, breathable membrane on its own is not breathable enough to prevent a build up of condensation in the loft area, the loft area also needs to be vented with the correct amount of insulation installed correctly to prevent heat escaping from inside the property into the loft area, with the loft area being vented to stop mother nature heating up the void between the insulation & the membrane ,
you basically have three issues were there is water ingress wither that be condensation or a leak,
the fact that the cement pointing is keeping water ingress in the stonework.
and lastly water ingress through the eroded stone work being trapped by the cement pointing,
depending on how thick the walls are will depend on how long it takes to dry out dampness dissipates at the rate of 1inch per month,
this is only my opining from the photos on show without actually looking at the house in question I can only be about 80% sure.
good luck alex

 

[Tman10]

Very many thanks guys for all your comments and suggestions.