Nervous about repointing in lime.....

[Suzy D]

We have lived in our 1890's solid wall red brick house for just over a year, we love it and so for thankfully we don't have any damp problems within the house. However, the walls outside are suffering a bit from bricks spalling and I want to get bricks turned or replaced to rectify this. I have had a number of people (all 'lime/heritage experts') look at the house and all have said that part of the problem with the bricks is that at some time in the past the walls have been repointed with cement based mortar. All have recommended raking out and replacing with a lime based mortar - this is the only consistent advice as beyond the basics the details of how, when and using exactly what mortar vary quite considerably. Having researched a lot in recent weeks and months lime pointing does seem the way to go, however I have also read a number of horror stories about house owners having considerable damaging water ingress problems after having walls repointed in lime. Admittedly, most of these do seem to be in recent times when rainfall in the UK has been prolonged and persistent. Obviously I don't want to spend a considerable amount of money to rectify one problem and create possibly a worse one. I have no way of easily knowing what plaster, mortar etc has been used over the years on the inside. Grateful for any advice and words of wisdom and whether being a brick property is less of a worry than if built in stone etc.

 

[Lacan07]

We have lived in our 1890's solid wall red brick house for just over a year, we love it and so for thankfully we don't have any damp problems within the house. However, the walls outside are suffering a bit from bricks spalling and I want to get bricks turned or replaced to rectify this. I have had a number of people (all 'lime/heritage experts') look at the house and all have said that part of the problem with the bricks is that at some time in the past the walls have been repointed with cement based mortar. All have recommended raking out and replacing with a lime based mortar - this is the only consistent advice as beyond the basics the details of how, when and using exactly what mortar vary quite considerably. Having researched a lot in recent weeks and months lime pointing does seem the way to go, however I have also read a number of horror stories about house owners having considerable damaging water ingress problems after having walls repointed in lime. Admittedly, most of these do seem to be in recent times when rainfall in the UK has been prolonged and persistent. Obviously I don't want to spend a considerable amount of money to rectify one problem and create possibly a worse one. I have no way of easily knowing what plaster, mortar etc has been used over the years on the inside. Grateful for any advice and words of wisdom and whether being a brick property is less of a worry than if built in stone etc.

I suspect you're worrying a bit too much, spalled bricks need to be turned or rendered as they have no protection against the elements having lost their glazed protective surface. So that certainly won't make your wall any more vulnerable.

And regardless of the cement mortar that's been used on your walls in the past replacing it with lime won't make it any less vulnerable to getting wet from driving rain, but it will help the wall recover quicker by allowing the moisture to escape from the mortar beds.

Solid brick or stone walls can be troublesome in exposed locations where rain is often accompanied by driving lateral winds, on hills etc. Giving the walls the best opportunity to recover and dry out is all you can do here, other than tiling them. In the main for most people with solid brick walls all that is required is to make sure all roof guttering and drains are sound and working well. Most of the time the biggest threat to a solid brick wall with soft reds is a leaky, blocked gutter that allows water to cascade down the side of it causing saturation.

 

[Cubist]

There are several possible causes of 'brick spalling' but the top two include; exposure of the top edge of the brick(s) creating a ledge that allows collection and absorption of rainwater or, use of an incorrect or improperly applied mortar during either original construction or later re-pointing. Both of these can lead to spalling either through water becoming trapped in the face and undergoing repeated freeze/thaw cycles to burst the face off the brick or by thermal cycling induced differential movement to produce the same/similar effects.

To my mind the people you have consulted are quite correct in their assessment and you should indeed rake out and replace the cement and replace it with a suitable lime mortar. However, given that it's now the wrong time of year for lime mortar work this project would be best left until the Spring of next year. At that time you could also 'turn' or replace the damaged bricks and ensure that the new pointing is correct in terms of its finish to the top edges of each brick. Also, and to echo Lacans point above, lime mortars are much more effective in their shedding of rainwater, whatever its source, than any cement based material.

 

[Suzy D]

Thanks for replies above. I think my concern is that one of the walls is quite a large tall gable that does get the rain and wind. Won't lime mortar let more rain in as well as letting more back out?

 

[Kearn]

You don’t say quite how many bricks are suffering. Turning soft bricks isn’t always that successful, your era may be less risky. But if there’s a lot, it’s not really a viable option.

If it’s very exposed to the elements, and the bricks have failed, they will absorb the rain. Even undamaged bricks are porous and will absorb. Lime pointing won’t increase any risks. But, if this is the case, you would be better off protecting the wall with lime render.

 

[Suzy D]

Thanks Kearn. On the gable that is quite large - about 50 m2 there are probably 70 or so bricks that need turning or replacing. Replacing will be the option if turning isn't viable. We probably can't lime render as the property is Grade 2 listed. I assume there is no other way of getting that extra protection? I have seen references to the 'breathable' brick creams but most seem not to believe the breathability claims from what I can see; seems odd that these treatments have been allowed on a few high profile listed buildings.

 

[Kearn]

Thanks Kearn. On the gable that is quite large - about 50 m2 there are probably 70 or so bricks that need turning or replacing. Replacing will be the option if turning isn't viable. We probably can't lime render as the property is Grade 2 listed. I assume there is no other way of getting that extra protection? I have seen references to the 'breathable' brick creams but most seem not to believe the breathability claims from what I can see; seems odd that these treatments have been allowed on a few high profile listed buildings.

You’d be surprised, listing, and conservation in general, is in my opinion focused on maintaining the longevity of the total building. Many folks get hung up on individual elements, often at the detriment to the total. It’s a philosophical debate we have on site at the moment very frequently…

So, listing doesn’t prevent limewashing/rendering necessary if it’s going to preserve the structural integrity of the building. Minimising harm to the significant elements of the building is the key goal in any LBC app.
Given its age, it’s less likely it was originally finished that way, but it might have been and if there’s evidence to support, it strengthens the argument to reinstate.

All this depends on your CO and how you present your argument, sprinkled with a bit of chance as sadly the process is wildly variable and highly subjective.

That’s a fair number of bricks to source if genuine reclaimed are needed. And they will look noticeable.

No, there’s no other way - breathable sealants are utter rubbish and shouldn’t be allowed to be marketed or sold. It’s an utter scam. And rather than being a waste of money, they are worse and will irreversibly damage your property.

 

[alexander]

it relatively easy to turn the bricks if they are face brick it becomes extremely more difficult if they are what looks like half bricks as these will go all the way through the wall. painting or rendering maybe the way forward as your local listings officer at the council on there opining of if your application would be successful before applying.

 

[Lacan07]

Exposed gable walls can be a problem, one of the downsides of having the privacy of an end of terrace or detached property

 

[mostly_wrong]

If I can hijack this - i have a similar situation. Previous owner's must have repointed in sand and cement, and we now have lots of spalled bricks. The new repointing seems to lift off quite easily, I'm not sure if that means it's not been done that deep or if it's just an indication of the freeze/thaw weakening it. Anyway the thing that's keeping me awake at night is that in one area the mortar from the same coarse has blown out all the way on the inside corner:



Closer up...



[btw if someone wants to tell me this has nothing to do with subsidence or anything structural, then please go right ahead.]

I intend to get all walls repointed with lime next year when the weather permits. But is there any way to protect areas like this through the winter? As Cubist mentioned, i've basically now got a ledge that is inviting water absorption into this course.