DAMP WALLS & LIME PLASTERING

[Nick]

I'm well in refurbishment of my stone / brick cottage and almost at the stage of thinking about reinstating plasterwork.

I’ve removed the original plaster and cement renders from the inside walls and have sought advice from various experts on plastering, damp control and lime.

Whilst I was going to go down the lime plaster route, I have been informed by several experts that whilst this is the right approach, one thing you cannot guarantee with lime is that the walls will remain free of staining or salt staining and on the basis that I’m spending a bucket full of money on this refurbishment (much more that I originally budgeted) I don’t want to plaster these walls and then find the walls are stained at a later date.

I want to achieve dry / stain free walls and been told I can achieve this by using a cavity membrane system with a plaster finish (which is a type of dry lining), overall cost not much different to lime plastering.

I have discussed this with the local Conservation Officer who has basically said NO and has said, I have to use lime.

Question...... If the CO is insistent that I use lime, despite what others have advised me, if it all goes wrong and I end up with damp stained decorations and plaster work, can I hold the CO / Council responsible. I assume that he is advising me in the position of a professional advisor and representative of the council.

After all if my surveyor gets it wrong I can sue him.

Anyone else experienced this problem?

All help / advice appreciated.

Nick

 

[Penners]

If the CO is insistent that I use lime, despite what others have advised me, if it all goes wrong and I end up with damp stained decorations and plaster work, can I hold the CO / Council responsible. I assume that he is advising me in the position of a professional advisor and representative of the council.

I'm not an expert on this, but I suggest that the CO is acting in the best interests of the building - which is his brief and his job. He's not advising you, he's instructing you as to the way that building must be treated.

I imagine (and I'm quite prepared for more expert folk to contradict me) that the extent to which you risk staining of your final decorations will be down to the way in which you approach the lime plastering project. As I understand it, lime plaster will allow the walls to breathe, and will be tolerant of mildly damp walls. But if the walls are very damp, then you may be advised to leave them free of any kind of plastering for a while, in order to allow them to dry out before you plaster.

I believe that this would be a beneficial thing to do anyway - particularly as we're coming into the warmer, drier months of the year.

But if you plaster the walls before they're dry, and later find that your final decorations become stained, I suspect that the CO would simply tell you that you didn't do the job properly.

I repeat: the CO is responsible to the building, not to you. Sorry to be blunt, but that's the way it is.

 

[Nick]

Penners, thank you for your prompt response.

Just a bit of back ground information. Walls are 15" solid brick, originally cement rendered and pointed, since which outside has been repointed with lime.

Internal walls stripped of plaster and have been left exposed for drying since last September. External drainage has been improved and I have done everything suggested. Walls have visibly dried down since initial stripping of internal render.

I appreciate that the CO has an interest in the building, so do I, that’s basically why I bought it in the first place, however I don’t have an endless pot of money and want to make sure that I get it right first time.

If I spend £5000 + having the interior walls rendered in lime (I'm employing specialist lime contractors so I would hope that they get it right!) and then find I’ve got damp staining then I’m not going to be very happy, as I’m sure you will appreciate.

It seems to me that as long as you’re not changing the appearance of the building or more importantly putting it at risk, then I don’t see the problem in using an alternative system of plastering.

Surely the CO / council has to be accountable, if they recommend something which is then proven to have failed or not worked?

Nick

 

[Flyfisher]

Hmm. I can understand your concern but I'm not sure a CO acts in a professional advisory capacity. It seems to be more of a regulatory capacity, i.e. telling you what you can and can't do to the property. As rightly pointed out above, the CO's responsibility is to the building rather than the owner.

Having said all that, have you discussed the CO's decision and the reasons behind it? After all, if you are very concerned about the staining risk of using lime then you have the option of replacing the original cement render and (gypsum?) plaster - assuming it was present at the time of listing - which might be less susceptible to staining.

I'm not suggesting this would be a good thing, but compared with replacing all the cement and gypsum, a form of dry-lining might be more acceptable to your CO.

 

[JoceAndChris]

Sorry I can't be much help regarding the two systems you're considering, but I've read hundreds of posts on here about lime plastering, have looked at lime plastering in people's houses, and have never heard anyone complain of staining to the decorations.

Moreover, much as I can understand you only want to decorate once that isn't likely to be the case unless you're planning on leaving your house in around 8 years' time. I know many people do make their decorations last far too long (we have 20 year old wallpaper here- looks dreadful), but the reality is most people want a redeccy in ten years or sooner.

My gut instinct would be to follow the advice of your CO, SPAB, all heritage literature and advice, and lime plaster, making sure you keep back a pot of paint or a roll of wallpaper for touching up should some staining occur. You'll probably want to touch up scuff marks in a few years anyway.

Good luck with whatever you decide, and keep us posted on how it all works out!

 

[Penners]

Internal walls stripped of plaster and have been left exposed for drying since last September. External drainage has been improved and I have done everything suggested. Walls have visibly dried down since initial stripping of internal render.

I appreciate that the CO has an interest in the building, so do I, that’s basically why I bought it in the first place, however I don’t have an endless pot of money and want to make sure that I get it right first time.

If I spend £5000 + having the interior walls rendered in lime (I'm employing specialist lime contractors so I would hope that they get it right!) and then find I’ve got damp staining then I’m not going to be very happy, as I’m sure you will appreciate.

It seems to me that as long as you’re not changing the appearance of the building or more importantly putting it at risk, then I don’t see the problem in using an alternative system of plastering.

Surely the CO / council has to be accountable, if they recommend something which is then proven to have failed or not worked?

Nick

It's good news that the bare masonry has been exposed since last September, and has dried considerably. The longer that you're able to extend that period into the summer months, the more you're likely to ameliorate that situation.

I entirely understand that your funds aren't limitless. Most of us on this forum are in the same boat. But this doesn't change the fact that the CO is charged with caring for the building and not for your funds, I'm afraid. If the work that you carry out ends up causing staining to your decorations, I imagine he is likely to point out that you should have taken more care in doing the work.

Having said all that (and I hope you understand that I'm trying to be realistic about your situation, rather than argumentative), I believe that, if you have carefully dried out the wall and done your best to remove the causes of the damp, then lime plastering is the best approach, and that your subsequent decorations (properly done) should be fine. And if you want to reduce your lime plastering costs, why not tackle on the job yourself? Many of us here have found that such things aren't as daunting as they might first appear to be. And there are courses you can take, for a preliminary grounding in techniques:

http://www.buildinglimesforum.org.uk/courses.htm

http://www.mikewye.co.uk/LimecoursePlastering.htm

Here's a handy little video: http://www.sustainablebuild.co.uk/video-lime-plastering.html

And this is a useful article: http://www.buildingconservation.com/articles/plaster/plaster.htm

 

[Nick]

Thanks again for your responses.

I've arranged a site meeting with the CO and his Boss to discuss the plastering.

The CO seems quite able to tell me what I can't use, so I will ask them to tell me what I can use and suggest that they give me an appropriate specification.

Nick

 

[jencast]

Are there any methods to dry the internal cavities of stone walls before lime plastering? My situation is that we have taken off the gable end cement render and have allowed it to dry. The internal walls were stripped back , a slurry was applied and after 4 months, the walls were still damp. The builder suggested a foam backing and dry wall then plaster. Now the walls are showing considerable damp again, the beams are molding, and damp patches appear on picture holes. I cant afford to remove internal render again at this point and wondered if there was any other solutions? Thanks, jencast

 

[Ushy M]

Are there any methods to dry the internal cavities of stone walls before lime plastering? My situation is that we have taken off the gable end cement render and have allowed it to dry. The internal walls were stripped back , a slurry was applied and after 4 months, the walls were still damp. The builder suggested a foam backing and dry wall then plaster. Now the walls are showing considerable damp again, the beams are molding, and damp patches appear on picture holes. I cant afford to remove internal render again at this point and wondered if there was any other solutions? Thanks, jencast

Jencast, we have damp on our gable end wall - no external render, but removed external cement pointing and internal cement plaster. We did that last September and have left it to dry out since as the wall is very (over 2') thick and I think advice on here was to leave it to dry for 1 month for every inch (depth) of stone. Did you leave the internal face of the wall long to dry out or was the slurry applied straight away?

Also, I'm no expert, (hopefully someone will be along soon who is), but the idea of a foam backing and drywall approach doesn't sound very breathable to me and I wonder if this would make the damp worse. Other than removing the render, I can't immediately think of a way round this one - sorry not to be more helpful.

 

[MdB]

Hi Jencast,

A few questions (sorry): What sort of slurry was applied and where and when? Is this on the internal wall or injected into the wall? What has been applied to the inside wall and what sort of finish is on top? The moisture around picture holes implies that something no breathable has been put onto the internal wall trapping the moisture which is then escaping causing the patches.

Pictures would be useful too.

 

[jencast]

The walls were stripped back in July 2008, they were dry walled and replastered. After a month of dehumidifying, the wall was still 70% wet so the builder applied a slurry product to the plaster, then installed a foam backed dry wall and again replastered and painted. We ran fires in the wood burning stove and used dehumidifiers 24/7. No damp for a year. New tenants moved in, and some damp showed up during the winter months of 2009, along the joints by the ceiling and corners, so we used dehumidifiers again. I touched up the patches in May 2010 with paint sealer, used dehumidifiers and the patches disappeared. Another set of tenants moved in, and now patches have increased along the seams/joints and picture holes. I suggested they run the dehumidifiers again and open windows for cross ventilation. I am thinking of taking off 5-6 inches of these plater layers all along the external walls at the bottom and the top of the interior walls to vent the moisture out. Taking the walls back to the original stone and leaving them exposed would be unslightly as the walls are made of slate, granite, cement block and brick. Over the years, the previous owners may have repaired these walls with whatever materials they could find. The house is 350 years old. During the summer of 2009, the electrics of one wall got completely wet, and the whole run along that wall to all the sockets needed replacing. I will try to download some pics shortly. Could I use airbricks on the interior of external walls? Initially, we thought the damp was due to condensation in the winter time, but now damp patches are appearing even though we have been dry for a month. Any suggestions and thoughts are appreciated.

 

[JoceAndChris]

Jencast - this sounds like a total nightmare and you have my sympathy.

 

[jencast]

Thank you. We took out some stones from the outside wall and it seems to be drying out well. Outer wall and internal cavity fill is mostly dry, but the inner skin is still damp. We have decided to install 8 airbricks angled downwards to air out the wall and install 3 drip lines. On the exterior walls, I will remove internal render around the base and the top on most walls. On a couple of the walls, the lower half will be taken back to stone and then a dado rail for the top half. If this works, then I will rerender in only lime and paint only in lime wash to match existing render. We will run dehumidifiers in the winter time and when we have rain. Hopefully I can save enough pennies to do remove the rest of the external render on the front wall and the back walls. Til then, we will manage somehow. Thanks again for the input.

 

[JoceAndChris]

Dear Jencast

I don't think we have given you a really vigorous response, you might get more responses from experts if you start your own thread with a new title? Just an idea...

It sounds like you're taking really good steps to address the problems though, and good luck with all that. Such a lot of work for you, and messy and expensive too.

With the dehumidifier, I can only suggest that you experiment a bit with it. It doesn't sound as if you're living there so it might be an idea to instruct your tenants with this.

During a wet winter, assess the damp with the dehumifier on and off. Try it in different places and see what happens. My own experience with running one for a year was interesting. When it was sited near to the cooker (I have a damp basement kitchen) it did seem to work well and suck up the moisture of cooking. Encouraged, I moved it to the dampest spot in the house, and it just seemed to pull out more and more moisture from the ground. In 3 months my old pamment floor became completely encrusted with white salting. I moved it to another spot, brushed all that white salting off, and the floor has looked much better since, and that bit of the kitchen has been less damp. I now only turn the thing on occasionally, as I just think it pulls moisture from the earth. I'm not sure if this is because the dehumidifier is sited in a partially sunk area, and how much the dehumidifier "creates" moisture in an above ground situation. I'd be interested to read other opinions on that. But certanily, opinions about them are divided.

With my own situation, until we can properly address the problem as you are it seems ventilation is much better than dehumidifying. The more the windows and doors are opened, the better the whole cottage is. It can be hard to get that message across to tenants though. I think in summer months a real effort at ventilation is crucial for old houses.


I'll be interested to read about how your modifications work out, so please keep us posted.

 

[Flyfisher]

With my own situation, until we can properly address the problem as you are it seems ventilation is much better than dehumidifying. The more the windows and doors are opened, the better the whole cottage is. It can be hard to get that message across to tenants though. I think in summer months a real effort at ventilation is crucial for old houses.

I really believe that's the crux of the matter. Plenty of ventilation and fresh air wafting through the entire house to dry out any accumulated dampness from the winter months and get the house in a good condition for next winter's onslaught. Historically, open fires would have provided warmth during the colder months but also, crucially, lots of ventilation as well.

The modern trends of draughtproofing and central heating tend to reduce ventilation and, while I can understand the reasons, I'm not convinced this creates an ideal environment for many period properties. It can be quite a dilemma.

 

[vicky whitworth]

We stripped the modern cement render off our internal walls and spent a fortune (which I don't begrudge in any way) lime plastering. We have three patches of damp low down on the walls that come and go according to weather conditions. When it's damp (which it is most of the time in Devon) the paint finish (breathable paint from Rose of Jericho) is darker than the rest of the walls. I think it looks most charming. It's a living creature, it mirrors the natural environment. It's that what happens in old buildings? My understanding is that if you love old buildings you have to love a little damp too. It hasn't killed us yet.

I have another part of the cottage where someone has bitumened the walls under a cement render. The walls there are constantly covered in condensation and a deep black mould forms. It's grim, nothing can breathe.

I know which I would prefer.

 

[JoceAndChris]

Gosh - how interesting.

Mmm, the beauty of limewash is it lends itself to a mottled uneven look- as you say - very historic and lovely.

 

[jencast]

Hi, I am back to report what we finally did to address the damp. After 2 roofers, 3 builders and the architect's opinion, we finally discovered a leaky overflow valve on the hot water tank that sat in the 1st floor airing cupboard. This January, we replaced the leaky valve, cut out the stained plaster and repatched with same. It has worked beautifully and much cheaper than the projections the roofers, 2 builders and architect's suggested. I think the moral of the experience we have had was to take one's time, explore ALL possibilities before embarking on expensive solutions. Replacing a newly slated roof that was 2 years old, stripping back plaster to the stone walling when we have just done that 2 years earlier, and re doing the lime rendering just didn't feel like the right solutions. The unsettling part to these solutions was that the staining to the plaster was brownish in color. The slow leaky overflow valve water mixed with some of the decayed timber rot powder and came out staining the plaster. My new tenants are in love with the property and are very conscious of airing the property when conditions allow. I have provided them with a condensation directive which incorporates many of the suggestions I have received on this forum. Thank you for all the help and suggestions. I hope my post can help someone else in the future.

 

[philpjuk100]

Just watched "homes under the hammer" this morning where the property "expert" told us that a first floor flat in neasden needed a new damp proof course! phil,(must stop watching telly and get back out to the workshop!)