Lime mortar pointing - water penetration

[CliffordPope]

"so as to produce a less breathable wall, given the driving rain. "


But my point was that breathability seems to be a complete red herring.
I don't really care whether the wall is breathable or not - my concern is that the mortar between the stones is porous, like wheatabisk. If you trickle water down the outside of the wall it seeps through and runs out on the inside. It appears to be the way houses were constructed around here in 1880, and they stopped them leaking by concrete rendering, or facing with slates or corrugated iron.

It would be a shame to re-render it all having just paid to have the old render removed, especially as the stone/brick contrast has been so nicely highlighted around the corners, windows and doors.
I bought into the concept of lime mortar and breathability because that's what all the experts on this forum and outside are plugging. But it doesn't work. Not on this house anyway. The only thing that works is modern chemical treatment, to mitigate the doubtless shoddy building methods of a century ago.

 

[MatthewC]

I do sympathise, but you have said how the position of the house is exposed to driving rain and south westerlies. I would guess that the house always been rendered since the day after the first occupant moved in, and possibly has always been wet. The (failed) cement render is probably just another attempt to hold back the forces of nature, just like the slates or corrugated iron which you mention.

But it doesn't work. Not on this house anyway. The only thing that works is modern chemical treatment, to mitigate the doubtless shoddy building methods of a century ago.

You could have said "The only thing that might work is modern chemical treatment which could mitigate the really bad weather this house has suffered in the last year or two (but even that might not)".

 

[malcolm]

I've been removing waterproof coatings from the outside bricks because they have trapped water where they failed and caused damp problems. In the east of England breathability has many advantages unless you happen to be a slug, woodlouse or beetle, or have a preference for damp mouldy walls. I accept that stones are more difficult - you get cracks which let water in.

The main thing if you care anything about the building must be to try to make sure anything you do is reversible. I don't know if it is possible to render over a silicone coated surface once it has failed or starts to cause other problems. It is not the solution I would have chosen.

 

[momo292]

Understanding lime's qualities as a building material isn't the complete picture; in the plainest terms, philosophically, there is something we all need to understand: water to a building - any building, much like the prospect of death to us mere mortals is inevitable - it will get you eventually! I suppose it's Mother Nature's way of telling us she cannot be contained. Ergo, with that in mind there are (broadly) two ways to manage moisture when constructing buildings: manage water, exclude water. Thus generally older buildings built with lime and featuring constant heat sources like Rayburns and the like were designed to allow water to penetrate the internals (in the form of vapour - not quite how you describe. Yours is a unique situation much like the article I linked to previously above) then evaporate away harmlessly. Think of Gore-Tex breathable shell jackets - lime works a lot like that in that these jackets stop rain droplets, but allow perspiration to escape in the form of water vapour.

I'm writing the above partly with thoughts to a curious novice coming along and reading you post below which would possibly work against conservation, something I am very interested in.

The point to make about lime as a breathable material is that it forms part of a complex interplay of elements that can afford buildings equilibrium with nature. For example windows and ventilation is another such element, as is whether the heating cycles on and off or stays on in a sustained fashion for several hours (allowing masonry to act as storage heaters, thus maintaining relative constant temperature). It's all a bit complicated, I suppose why this forum exists

Anyway not to make it at all personal - solutions are great and I am glad you found yours. All the best and good luck for the future.

"so as to produce a less breathable wall, given the driving rain. "


But my point was that breathability seems to be a complete red herring.
I don't really care whether the wall is breathable or not - my concern is that the mortar between the stones is porous, like wheatabisk. If you trickle water down the outside of the wall it seeps through and runs out on the inside. It appears to be the way houses were constructed around here in 1880, and they stopped them leaking by concrete rendering, or facing with slates or corrugated iron.

It would be a shame to re-render it all having just paid to have the old render removed, especially as the stone/brick contrast has been so nicely highlighted around the corners, windows and doors.
I bought into the concept of lime mortar and breathability because that's what all the experts on this forum and outside are plugging. But it doesn't work. Not on this house anyway. The only thing that works is modern chemical treatment, to mitigate the doubtless shoddy building methods of a century ago.

 

[MatthewC]

...something we all need to understand: water to a building ... it will get you eventually! I suppose it's Mother Nature's way of telling us she cannot be contained. Ergo, with that in mind there are (broadly) two ways to manage moisture when constructing buildings: manage water, exclude water.

I first learned about that a few years ago. SPAB were running a Lottery-funded programme called "Faith in Maintenance" (a quote from William Morris); this course was designed to educate churchwardens about their responsibilities for the building. The course director (an architect) started off by saying "if you look after the water that falls on the roof, runs in gutters and downpipes and goes away from the building in drains, then the building will not fall down on your watch". This course summary echoed through my head when I first saw this house, which I would not have bought had I not done that course.

 

[momo292]

Lovely quote Matthew, thanks for sharing. Here is another I have tried to carve into my mind, also from William Morris: “We are only trustees for those that come after us.”

By the way not entirely on topic but the philosophy of either stopping nature or going with it is expressed rather eloquently in this lovely short documentary about a Japanese woodworker who is now based in the US, well worth a watch:

Building Without Nails The Genius of Japanese Carpentry
https://www.youtube.com/watch?v=rMtSc2MJLcw

 

[Flyfisher]

The course director (an architect) started off by saying "if you look after the water that falls on the roof, runs in gutters and downpipes and goes away from the building in drains, then the building will not fall down on your watch".

I also like that quote and feel that I learned a great deal about such things during our repair works just by walking around our scaffolding in the pouring rain and watching where and how the water flowed. I'm still not averse to walking around the house in the pouring rain just to check everything is as it should be (though I admit I tend to only do this during summer showers). It's surprising (well, it surprised me) how a small area of faulty guttering or flashing can result in water pouring down a wall unnoticed to anyone sheltering (quite sensibly) inside, yet stops almost as soon as the rain ceases.

I like to think I'm doing my bit to ensure the house doesn't fall down on my watch.

 

[MatthewC]

...I learned a great deal about such things during our repair works just by walking around our scaffolding in the pouring rain and watching where and how the water flowed. I'm still not averse to walking around the house in the pouring rain just to check everything is as it should be (though I admit I tend to only do this during summer showers).

Doing that with a big umbrella and pair of binoculars was one of the practical actions recommended to churchwardens on that course!

NB Thinking of fighting nature, King Canute was not really trying to stop the tide coming in, he was actually demonstrating that he knew he was not as powerful as people thought. Poor bloke, good idea, bad press for centuries!

 

[Mickey]

Hi All,

As you may have seen on the news Cornwall is getting a fairly tough time of the weather recently...understatement.....we still have not solved water penetration through our newish lime pointing on the face of our building which gets all the weather, at the moment that's been rain being blown at the building at 50 miles an hour! Conditions have been consistently wet since November and these particular walls just can't take any more. I'm dreaming of being able to lime render the front but it's listed and there is no way our CO would agree to it. Anyway, the result of all this is very very wet walls yet again in the main bedroom and staining coming through the limewash (I'm convinced that running the dehumidifiers has pulled these stains through). I am not confident that when (if!) this wall dries out limewash will cover these stains and an internet search has led me to this stuff I just wondered if anyone had an experience with it, I am a bit nervous re it's breathability claims having shelled out for lime pointing, lime plastering and lime washing I don't want the breathability compromised.

http://www.paintedpast.co.uk/datasheets/EliteHeritage.pdf

I am trying to keep the faith where these front walls are concerned but I fear that the problem is the washing out of rubble from the interior leaving voids possibly combined with rodent (oh yes another little problem we have) tunnelling, from what I have read the rectification by filling voids (lime slurry) in these walls is very difficult.....I'd love it however if someone can give me hope that it's otherwise, the project is turning into a labour of hate at the moment!

PS. What I will say however, in defence of lime is that the water penetration is much much less now we have lime pointing and lime render on the inside because when it was cement pointing, bits of cement rendering on the inside covered in Black Jack and then plasterboard dry lining we had 5 buckets in that room catching the water!!

Cheers
Mickey

 

[momo292]

Hi Mickey,

I am sadly not familiar with the product you cite, however understand that historically the practice had been to add tallow to limewash to aid water shedding properties. It somewhat reduces breathability, so one has to not be too liberal in adding tallow, but this is historical practice that is well documented so you CO should have no problem with it, especially internally.

This is a site I have enjoyed browsing recently, very basic but wonderful - some good articles there and the owner of the company has written several excellent articles out there on the web and on his own website. Anyway here is a product sold there that may be worth your consideration: http://www.rose-of-jericho.demon.co.uk/products/rj3_03.htm.

Best of luck,
Momo