I have cement rendered timber frame walls that having ripped off the plasterboard are showing serious signs of rot because of condensation. Currently I don't have the option of removing the cement render and re-rendering. What is the best way to stop the condensation? Should I try and seal the cavity with an impermeable membrane or leave it more open to ventilate naturally? I would like to insulate between the beams at the same time. Is there a temporary solution (maybe 1-2 years) to preserve things until I can replace the render? Thanks!!
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Feltwell
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Leaving it open to ventilate definitely sounds like the way to go to me, seal it up again in any way and your problem is likely to return.
However, timber frame is not something I have much knowledge on at all, others on here know far more than I do and will no doubt offer you a more qualified opinion as to your best way forward.
However, timber frame is not something I have much knowledge on at all, others on here know far more than I do and will no doubt offer you a more qualified opinion as to your best way forward.
tobydog
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Whilst I haven't read it all yet, I have found a very interesting article on the subject of breathability. See the link below. It looks well written, easy to read and will appeal to all levels of interest. I would be interested to hear from those who know more about these things than I do as to how good it really is. I share the same issues as you worly but maybe not to the same extent.
http://www.greensteps.co.uk/tmp/assets/1163178050906.pdf
http://www.greensteps.co.uk/tmp/assets/1163178050906.pdf
Flyfisher
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Welcome to the forum worly. Could you post a photo of the wall in question as that may help the resident experts form an opinion.
Immediate question that spring to my mind:
1. what sort of infill material is between the timber frame (if any?)
2. are you certain it's a condensation problem (usually from inside the house) or could it be rainwater seeping in through cracks in the external render?
3. what does "serious signs of rot" actually mean (again, photos will help)? Is it fairly superficial or is it right through the affected timbers? Have you tried pushing a nail or other sharp object into the timbers? How far does it penetrate before hitting hard wood?
My feeling is that you've already started the remedial process by exposing the timbers and the resulting ventilation should allow things to dry out, though it may take some time depending on the ambient conditions.
While things are drying out you'll have plenty of time to develop a more sympathetic long-term solution. If, as seems likely, such a solution involves replacing cement render with a breathable lime render then there is no immediate rush because lime work cannot normally be done during the winter months anyway.
Meanwhile, don't panic - you're doing the right things so far.
Immediate question that spring to my mind:
1. what sort of infill material is between the timber frame (if any?)
2. are you certain it's a condensation problem (usually from inside the house) or could it be rainwater seeping in through cracks in the external render?
3. what does "serious signs of rot" actually mean (again, photos will help)? Is it fairly superficial or is it right through the affected timbers? Have you tried pushing a nail or other sharp object into the timbers? How far does it penetrate before hitting hard wood?
My feeling is that you've already started the remedial process by exposing the timbers and the resulting ventilation should allow things to dry out, though it may take some time depending on the ambient conditions.
While things are drying out you'll have plenty of time to develop a more sympathetic long-term solution. If, as seems likely, such a solution involves replacing cement render with a breathable lime render then there is no immediate rush because lime work cannot normally be done during the winter months anyway.
Meanwhile, don't panic - you're doing the right things so far.
stuart45
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If you are insulating between the timbers, you should add a vapour check on the warm side, or you could get even more condensation on the render as it will be even colder.
Zebra
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I have the same. Cement render on timber frame.
Heat and ventilation would be the things to let them dry out, and while you'vegot the cement on the outside, I wouldn't put any more barriers that will trap moisture. I can't really offer much advice as there are others on here far more knowledgeable, just was posting to say I've got the same thing, so we could perhaps observe each other's progress!
My plan is to remove the cement render next year and replace with a woodfibre based external wall insulation, with sheepswool between the beams.
Heat and ventilation would be the things to let them dry out, and while you'vegot the cement on the outside, I wouldn't put any more barriers that will trap moisture. I can't really offer much advice as there are others on here far more knowledgeable, just was posting to say I've got the same thing, so we could perhaps observe each other's progress!
My plan is to remove the cement render next year and replace with a woodfibre based external wall insulation, with sheepswool between the beams.
Thanks for all your comments so far;
The photo shows the worst part, it is decayed to about 10 mm from the sides of the beam in contact with the felt but the rest is sound and has dried out now. Everywhere the beams touch the felt there is some decay which is why I thought it might be condensation. It could be caused by ingress of water as the render has clearly been repaired in recent times. There was no infill between the beams so I tried putting sheep wool in, but was concerned about the amount of condensation build-up behind it. I tried putting impermeable membrane on top, and whilst this reduced the condensation it did not stop it (probably due to the number of gaps everywhere eg ceiling). Should I be worried about this? I am hoping to put lathe and lime plaster over the top, but in the short term what would be best?
stuart45
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A modern timber frame would have a breather membrane on the external side to allow moisture to escape, but prevent water getting in.
On the warm side of the insulation a membrane like pro clima intello plus could be used. You do have to make sure that the membrane is well sealed.
When timber frames first started being used in the UK this was often neglected caused damp problems.
On the warm side of the insulation a membrane like pro clima intello plus could be used. You do have to make sure that the membrane is well sealed.
When timber frames first started being used in the UK this was often neglected caused damp problems.
Keithj
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I don't like the idea of roofing felt inside the wall. Perhaps it's me, but that sounds like a good device to keep the damp in place while it rots the timber.
Some of our walls still have cement render, but only in panels that don't come down to sole plate level. We had to have all the sole plates and a fair number of the studs replaced, and once any concrete was removed, the whole concrete panel came out. The replacement is lime render. Where the remaining concrete is, there is no sign of damp or rot.
There is plasterboard on the inside of the concrete, with no "damp proof" material, and all seems well.
In the gable end wall, there was much felt as well as the concrete, and the whole gable end had to be replaced. It was sad seeing 16th Century timber removed because it had rotted beyond repair.
Some of our walls still have cement render, but only in panels that don't come down to sole plate level. We had to have all the sole plates and a fair number of the studs replaced, and once any concrete was removed, the whole concrete panel came out. The replacement is lime render. Where the remaining concrete is, there is no sign of damp or rot.
There is plasterboard on the inside of the concrete, with no "damp proof" material, and all seems well.
In the gable end wall, there was much felt as well as the concrete, and the whole gable end had to be replaced. It was sad seeing 16th Century timber removed because it had rotted beyond repair.
Most of the decay on the outward facing oak wall studs " faces " would have been there before before the ( roofing ?) felt and cement render was applied externally.
Just by looking at the photo, those studs don't appear to be in a bad state and in reasonably good condition give their age ( about 300 years, I suspect).
Obviously a mistake using that ( nearly) impermeable felt on the studs and aggravated further by adding cement render ( externally ??).
It is a quite common mistake some builders make, not because they are bad builders it is because they are a bit naive as to how these traditional timber buildings behave when modern materials are introduced in their fabric. If the cement render is sound ( ie, no cracks or obvious rain water entry points) your condensation will happen when the warmer ( and water laden ) air condenses on the cold interior face of that " roofing" felt which is kept permanently cold by the cement . Very prominent during the winter months, as can one immagine. In the summer the problem will disappear.
These kind of well intentioned repairs have been ( and are) fast tracking the decay process of these buildings.
Obviously if ventilation and warm air movement is increased across the inner surface of the felt, the condensed moisture will be dissipated with no ill effect. Unfortunately this is not easily achieved if the external render and felt are left in position, and quite expensive to heat the building whilst allowing for enough ventilation to dissipate accumulted misture on that inner felt surface.
There is no need to panic for the next year or two ( having stood for 300 years it is not going to disintegrate ove the next couple). If you intend to remove that render and felt ( as you should), perhaps it would be a good idea to use all the time you have ,before you actually do it, to learn as much as possible about traditionally constructed oak frame building and formulated a plan of attack as to how you need to do it .
You are on the right track so far by asking questions.
Middi
Just by looking at the photo, those studs don't appear to be in a bad state and in reasonably good condition give their age ( about 300 years, I suspect).
Obviously a mistake using that ( nearly) impermeable felt on the studs and aggravated further by adding cement render ( externally ??).
It is a quite common mistake some builders make, not because they are bad builders it is because they are a bit naive as to how these traditional timber buildings behave when modern materials are introduced in their fabric. If the cement render is sound ( ie, no cracks or obvious rain water entry points) your condensation will happen when the warmer ( and water laden ) air condenses on the cold interior face of that " roofing" felt which is kept permanently cold by the cement . Very prominent during the winter months, as can one immagine. In the summer the problem will disappear.
These kind of well intentioned repairs have been ( and are) fast tracking the decay process of these buildings.
Obviously if ventilation and warm air movement is increased across the inner surface of the felt, the condensed moisture will be dissipated with no ill effect. Unfortunately this is not easily achieved if the external render and felt are left in position, and quite expensive to heat the building whilst allowing for enough ventilation to dissipate accumulted misture on that inner felt surface.
There is no need to panic for the next year or two ( having stood for 300 years it is not going to disintegrate ove the next couple). If you intend to remove that render and felt ( as you should), perhaps it would be a good idea to use all the time you have ,before you actually do it, to learn as much as possible about traditionally constructed oak frame building and formulated a plan of attack as to how you need to do it .
You are on the right track so far by asking questions.
Middi
In addition to my previous post, I would like to add that there are different possible ways to insulate and preserve the building framework.
Modern insulation materials and breatheable membranes can be used to exellent effect as long as they are used correctly and in context with the present structure and it's need for ventilation requirements. Incorrectly applied these " modern" materials are a fast way to destruction.
As to your idea of insulating between the studs ,as a temporary measure, and perhaps using a non breatheable membrane, It may save you some money in heating bills but will not do very much to improve condensation deposits on the inner surfaces of the membranes. This water acculmulation will form " puddles" on the cill plate speeding up decay and a damp base wall.
I have experienced walls constructed ( repaired !! ) in the very same manner as your picture with the addition of rockwall insulation under plaster board between studs, the complete rockwall was " soaked " ( albeit,up to the water repellant percentage ) and the base wall and plate completely saturated.
Apart from the obvious and traditionally exercised method of wall construction, ie- wattle and daub with exposed or boarded exterior, the better way is to eventually insulate the exterior of the building with modern ins. fabric and breatheable membraned with further insulation between studs and breather membrane.
A lot of what you will eventually do will be dictated by you budget, the requirements of the CO ( if applicable) and the method you will eventually decide upon.
Middi
Modern insulation materials and breatheable membranes can be used to exellent effect as long as they are used correctly and in context with the present structure and it's need for ventilation requirements. Incorrectly applied these " modern" materials are a fast way to destruction.
As to your idea of insulating between the studs ,as a temporary measure, and perhaps using a non breatheable membrane, It may save you some money in heating bills but will not do very much to improve condensation deposits on the inner surfaces of the membranes. This water acculmulation will form " puddles" on the cill plate speeding up decay and a damp base wall.
I have experienced walls constructed ( repaired !! ) in the very same manner as your picture with the addition of rockwall insulation under plaster board between studs, the complete rockwall was " soaked " ( albeit,up to the water repellant percentage ) and the base wall and plate completely saturated.
Apart from the obvious and traditionally exercised method of wall construction, ie- wattle and daub with exposed or boarded exterior, the better way is to eventually insulate the exterior of the building with modern ins. fabric and breatheable membraned with further insulation between studs and breather membrane.
A lot of what you will eventually do will be dictated by you budget, the requirements of the CO ( if applicable) and the method you will eventually decide upon.
Middi
Keithj
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Ours, where repaired, are lime render on the outside, wool insulation, and plasterboard and skim on the inside. The folks doing it knew their stuff, and I assume have done it right. They were certainly scathing about the earlier builder who applied the concrete.
Keithj said:
Lime render, breather membrane and breatheable insulation will work fine. Plasterboard internally it is also fine ( good breatheable qualities),
( as long as one does not mind deviating from a " purist" museum style restoration). Simple effective , and best of all, materials easily available and does not break the bank.
Middi