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| Ed K: (26/10/05) | Internal walls - solid granite - lime plastering ? |
| Hi
I have an old cottage with solid granite walls. The internal walls are plastered with lime plaster direct onto the granite walls. This is damp in places so I removed it and let the walls dry out over the summer (the problem was that the room was tanked - no need as the damp can be solved by french drain and adding gutters to the roof.. I hope :)) Well I can replace the lime plaster or I can use 42mm Gyproc Thermal Board Plus. Any ideas ? Externally I was going to strip off the plaster which is cracking and use a lime plaster and lime wash (more maintenace I guess.) Cheers if you can offer any experience or advice on lime plasters... Ed | |
| david hyde: (28/10/05) | RE: Internal walls - solid granite - lime plastering ? |
| sorry Ed you dont know what you are talking about.
Ok so you have got some damp lime/ie old plaster on internal walls. These could not have been tanked (a waterproof render or coating to stop penetrating damp normally under pressure ie below ground. If they were tanked and the plaster was damp then you were experiencing condensation and I wont go into that one now. If the plaster was damp then this was, assuming no complcating factors like leaking plumbing or dogs peeing up the wall, the result of rising damp. This rises through the lime mortar joints. Shock/horror how can that be we all know that lime mortar cures most ills known to diy addicts. Ok so you fitted some gutters and broke your back installing a french drain. Does it drain? how far have you managed to lower the water table to be able to control or reduce the rising damp. I trust that the gutters are led to a drain and away from the building. This could reduce the severity of the rising damp if you wait long enough. However, you have now got a contaminated wall, loaded with salts, hygroscopic salts, These absorb moisture and make the wall look damp! It is quite easy for these to be transmitted to any plaster coating that you apply to the wall, you can I hope guess what happens next, yes,you get damp patches on the wall! Now you start discussing what to do about defective lime plaster? externally. This cant have anything to do with your original question. I am worried that you actually meant not internal walls but the internal surfaces of the external walls! If you want to come back with some clearer description of the problem and not what you think it is, I might be able to help. Regards david | |
| Ed K: (28/10/05) | RE: Internal walls - solid granite - lime plastering ? |
| Hi David
Yes I agree, I know next to nothing but I am humbly trying to learn ! The walls in the front room were as follows : From the ground up to 1.3m : Wallpaper... Pink plaster skim of about 3 or 4 mm. Behind that cement of about 10mm. Behind that a coating of bitumen. Behind that very very hard concrete to even out the granite wall. Behind that the granite wall. This is inside the room. The cement and pink plaster was loose so i chipped it off and found the bitumen and concrete. I decided to pick that off too. Above that is the original lime plaster. The first 30cm or so of it above the line of the concrete/bitumen is damp. Or it looks damp at least. The outside is what I am guessing to be a similar lime based render with paint over it. So I have a damp wall up to the first metre or so - what do you do about it ? If you have any words of wisdom then I would be glad to hear of them. So far all I have done is the guttering (last winter), picked off the internal plaster/cement/concrete and let the whole lot air for the summer. Yes lime has a good rep - I assumed that lime allowed for even absorbtion/release of water in solid walls. So lets say I start with my solid granite wall in its raw state with no internal or external render/plaster .... what would you do... Cheers Ed | |
| Ed K: (28/10/05) | RE: Internal walls - solid granite - lime plastering ? |
| A couple of pictures of how it looked after the wallpaper had come off :
http://www.noncreative.com/house/web_sl_front1.jpg http://www.noncreative.com/house/web_sl_front2.jpg Yes I know that links are frowned upon on this site but it is not advertising anything and I think it serves to illustrate my problem... Ed | |
| david hyde: (02/11/05) | RE: Internal walls - solid granite - lime plastering ? |
| Ok thanks, I am getting a better picture.
You are probably seeing the results of the intervention of various people over many years. There could easily be both rising and penetrating damp in your walls. You do have a combination that could be described as tanking. However, I think that most of the current problems are probably due to condensation. I would certainly get rid of the plaster coating. Any other coatings should be dealt with by my usual method. namely hit it with a hammer, if it falls off, good, if it doesn't thats ok too. I would then dry line and insulate over these remaining coatings. There are traditional methods that joiners and builders use but you may wish to looke at the other line curently running from Paul Cooper? on how to insulate a cottage. We can talk about your other dampness problems later. | |
| (GBP) Keith: (03/11/05) | RE: Internal walls - solid granite - lime plastering ? |
| Hi Ed. The links to photos that you have used are a good idea and great for iillustrating your question. Other board users are welcome to do the same.
We only frown upon, as you say, blatent advertising or innappropriate content links and in those cases we remove within hours and may ban the user. But what you have done here is fine. Regards Keith | |
| Ed K: (03/11/05) | RE: Internal walls - solid granite - lime plastering ? |
| Thanks Keith - there is also space available on a site called shutterbook - might be worth using if people want to illustrate posts...
Any more thoughts on lime plastering ? I am of a mind to strip off all the plaster as it looks pretty chipped (from previous wallpaper removal I think) and will be hard to join if I tried to patch the parts that have been picked back. So rising and penetrating damp ? How to cure this in a solid wall house ? Thanks for any advice / help / words of wisdom :) Ed | |
| Ed K: (06/11/05) | RE: Internal walls - solid granite - lime plastering ? |
| Any more advice on this problem ?
I have now decided to strip all the old lime plaster off from the whole house. The reason being that it is pretty chipped and sounds like it has blown in various places. As I will be doing alot of other work to the house I thought it might be easier to start from scratch as far as the plastering goes. But as far as resurfacing the walls I am in two minds. A builder friend came round today and said that most people over here just use insulated plasterboard (Thermoboard as mentioned in first post). i.e. the wall is rough rendered and then the board stuck on. Hence no condensation. (i.e. the walls outer surface is cold but with modern heating and well draught-proofed houses the inner surface of the wall heats up = condensation. But by using insulated plasterboard you stop this condensation problem). However I am still worried by the previous posters comment about rising damp and salts in the wall soaking up water (rising damp). If I use Thermoboard this would seem to ignore the rising damp and I am not sure what problems this will create later on. Any advice ? Many thanks Ed | |
| david hyde: (09/11/05) | RE: Internal walls - solid granite - lime plastering ? |
| Hi Ed its me again. I have looked at your pictures and you have the tide mark of classic rising damp. Seems a bit high for a granite wall but your dense cement render will produce this effect. To damp proof or not to damp proof? that is the first question. In granite walls I would only recommend Lectros Active electroosmotic DPC. Installed from one side ie inside or outside. Outside you will have extra work to hide the circuit wire.
Inside you will need to dry line, please don't consider any finishes direct onto the walls (salt contamination condensation etc.) Insulated plaster board will work but your builder is proposing dot and dab procedure. What is he using? Gypsum plaster commonly used will fail. You also have the potential for condesation on the wall. If you don't see why read the discussion on shuttered windows, the same logic applies. My recommedation would be to fix a cavity drainage membrane to the wall, this will isolate the wall and ventilate the void space. Then mechanically fix an insulated plasterboard with a skim finish. This is for the external walls simpler methods can be used on internal walls. Why are you removing all of the lime plaster? is it failing? or very easily removed showing that the bond to the wall has weakened. If so OK, if you need to chisel it of then it probably can be left. | |
| Konrad Fischer: (18/11/05) | RE: Internal walls - solid granite - lime plastering ? |
| Hi Ed
please do not believe anything about rising damp and insulation. There is nothing true about it. You have condensation and salts in your wall and only a resorbing layer can help to take out the salts. And besides you should avoid to have damp and wet air condensation in the cold wall surfaces. There are some possibilities, to warm up the walls like better heating. Your lime plaster you should keep intact, insulation methods will do the situation worse by sucking in moisture! You will find english and german informations on the following links: <a href="http://www.konrad-fischer-info.de">Information for Old Buildings Preservation</a> <a href="http://www.konrad-fischer-info.de/2auffen.htm">The Fraud with Rising Damp</a> <a href="http://www.konrad-fischer-info.de/2rilem.htm">Using Lime Mortar</a> <a href="http://www.konrad-fischer-info.de/213baust.htm">Insulation will not work insulating</a> and you can use goggle translation tool for better understanding my german texts. Good luck! | |
| david hyde: (20/11/05) | RE: Internal walls - solid granite - lime plastering ? |
| I have spent the last twenty years determining whether walls are affected by rising damp. Not with "moisture meters" but by taking samples and doing full analyses. Sometimes they are and sometimes they are not. However common sense says that sitting a porous material on a damp substrate will lead to dampness transferring from one to the other. The porous material in your case is the mortar.
If you have any doubts I will offer to do the analysis for you. You take the samples according to my instructions and I will do the analysis. Regards david. | |
| david email= iandavidben@aol.com: (22/11/05) | RE: waterproofing, damp walls, etc |
| We've heard about maragite. Apparently you can waterproof just about anything with it, even put into plaster for casting - any knowledge? | |
| david hyde: (22/11/05) | RE: Internal walls - solid granite - lime plastering ? |
| Why would you want to waterproof just about anything. If you reread this thread you will see that Ed reckoned that his walls were "tanked". This was probably a dense cement render and this has either caused his problem or sertainly made it worse. It would push the rising damp higher and would also make condensation more likely.
This siter gets lots of enquiries as to how to deal with damp surfaces and applying a waterproof something is almost never the answer. | |
| Susan Howes: (27/11/05) | RE: damp in granite walls |
| We have just bought a small terraced granite cottage (in Cornwall, built c1850), some of the internal walls are plastered, most are not which we prefer.
The survey we had carried out mentioned that there is no damp course. Is it usual to have a damp course in granite buildings? How hard/necessary is it to have one added at this stage? Also, we've realised that the walls on the inside of the windows are damp to the touch around the windows, to a depth of about 6" into the house, both those which have been plastered and those which are bare granite. Is this usual? We've not owned a granite built house before and are now sure what we should expect to live with, and what we should be putting right? | |
| Rod Evans: (28/11/05) | RE: Internal walls - solid granite - lime plastering ? |
| Hi David,
I've read this thread with interest, but haven't completely understood the best way of treating a damp internal wall. It's a 200 year old house, no DPC, and rough build (mixture of stone, mortar and brick walls) with plaster ave. 2.5cms thick. I've stripped off about a square metre of plaster, to a height of 60cms to let the wall dry out. At the base of the wall, behind, and below the depth of, the skirting board, there appears to be soft damp soil. To repair the wall should I try to seal the brickwork and then put in some polythene membrane in a U-shape behind the skirting, blocking off the damp soil and back up the wall before plastering? Or not?! And then re-plaster - any advice on the correct plaster to use? How long to leave it before wall-papering? Thanks for any help you can give. | |
| david hyde: (29/11/05) | RE: Internal walls - solid granite - lime plastering ? |
| Susan
Granite is a very poor insulator and therefore will be cold when the weather is cold. You will get condensation as a result. If you want to see attractive granite walls you will just have to turn the thermostat up. You can get rising damp in these walls via the mortar joints. Curing it is probably quite low priority as the overall detrimental effect on the structure is quite small. The most effective DPC in these walls would be the lectros active electrosmotic system. | |
| david hyde: (29/11/05) | RE: Internal walls - solid granite - lime plastering ? |
| Hi Rod
Internal wall, single brick? Sounds as though you have rising damp if the plaster came off easily. The debris you describe makes me question what if anything you wall is sitting on. I have seen them built off a tree trunk, which of course doesn't last for ever. You should do some more probing before we get on to replastering. | |
| Rod Evans: (01/12/05) | RE: Internal walls - solid granite - lime plastering ? |
| It's the dividing wall with the terraced house next door, David. Built on a low hill in Keswick (Lake District) where I suspect there's a lot of rock below the surface. Solid slate floor up to the skirting boards, but you get little resistance to a probe between the brick wall and the skirting. The wall feels quite dry at the moment! | |
| david hyde: (01/12/05) | RE: Internal walls - solid granite - lime plastering ? |
| You will need to take the skirting off. Firstly does it look old or was it recently installed. It will tell you whether you have dampness because if so it will show signs of decay. You must explore what the wall is built on, soft brown stuff is not acceptable. Be careful you don't poke through into next door! | |
| Rod Evans: (03/12/05) | RE: Internal walls - solid granite - lime plastering ? |
| Thanks David. The skirting is original and in good condition, now I've given it a chance to dry out thoroughly. Loath to take it off - I'd prefer to take a chance on having cured the problem, now that all the old plaster and rubble has been taken away. There's a half-inch gap between slate slab floor and brick wall, into which you can plunge a screwdriver to a depth of at least six inches. What would happen if I sealed the gap between slate floor and wall with a waterproof filler? | |
| david hyde: (04/12/05) | RE: Internal walls - solid granite - lime plastering ? |
| We havn't really established why your wall was damp in the first place that caused you to strip off the plaster. Rising damp is the most likely explanation but I would have expected the skirting to show signs of decay.
You can clean out the joint between the floor and the wall and fill with a normal cement mix. Don't seal the brickwork, that will force any rising damp further up the wall. The most reliable method of replastering is to use a plaster membrane as a base material. This will isolate the wall from your plaster finish and also allow some air movement next to the wall. Use Delta PT or Delta lath or Newlath, these last two come in 15m2 rolls. Once fixed you can finish with almost any plaster, Carlite Bonding would probably be a good choice. | |
| Rod Evans: (04/12/05) | RE: Internal walls - solid granite - lime plastering ? |
| Thanks very much David. I'll follow your recommendations to the letter. It should be good for quite a few years after that - we originally noticed the problem in very minor-seeming form seven years ago - when the wallpaped started peeling off! | |
| david hyde: (06/12/05) | RE: Internal walls - solid granite - lime plastering ? |
| The other good news about this procedure is that it is surveyor proof. You dont get any readings on a moisture meter! | |
| iandavidben@aol.com: (30/12/05) | RE: Internal walls - solid granite - lime plastering ? |
| Re: earlier posting on good waterproofing stuff - someone e-mailed uss with link for <a href="http://www.maragon.co.uk/resin.html" title="http://www.maragon.co.uk/resin.html" class="InPostLink">http://www.maragon.co.uk/resin.html</a> maragite. We've used it in a basement extension - it's early days, but the difference between new and old is obvious. | |
| iandavidben@aol.com: (30/12/05) | RE: Internal walls - solid granite - lime plastering ? |
| Re: earlier posting on good waterproofing stuff - someone e-mailed uss with link for <a href="http://www.maragon.co.uk/resin.html" title="http://www.maragon.co.uk/resin.html" class="InPostLink">http://www.maragon.co.uk/resin.html maragite. We've used it in a basement extension - it's early days, but the difference between new and old is obvious. | |
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