Insulating floor of an old stone house
Discussion
I’m renovating an old stone cottage in North Wales and I wish to upgrade the insulation as much as possible and I’m planning to use more natural materials in order to allow the house to ‘breath’.
The place seems to have suffered with damp in the past as there is a strong smell of mildew. I believe this may be to do with the fact that the place was renovated in the 70’s with cement render on the external walls, cement pointing to the stone work. Cement/ plaster internally and concrete floor slabs with no insulation (but it does have a plastic sheet under the slab).
The roof needs to be stripped off completely, re-slated and timbers replaced, so I’m planning to use wood fibre insulation sarking over the new rafters with either wood fibre or wool between the rafters.
The walls (about 600mm thick) will have all the cement render/ plaster and pointing hacked off and re plastered with Lime. I may also fix wood fibre board internally.
With the floor, I would like to insulate the floor and have UFH and am prepared to break up the existing concrete to lay new floors but have read conflicting advice on how to proceed.
Some claim that an old stone building should have a breathable floor so that moisture from the ground is not pushed into the walls.
Whereas elsewhere i have read that a modern floor (DPM, insulation & concrete) will be better as it prevents water vapour entering from the ground through the floor which will create internal humidity.
I am far from an expert on the matter and am seeking to learn more. If anyone has experience in this area I would appreciate all comments. Thank you
The place seems to have suffered with damp in the past as there is a strong smell of mildew. I believe this may be to do with the fact that the place was renovated in the 70’s with cement render on the external walls, cement pointing to the stone work. Cement/ plaster internally and concrete floor slabs with no insulation (but it does have a plastic sheet under the slab).
The roof needs to be stripped off completely, re-slated and timbers replaced, so I’m planning to use wood fibre insulation sarking over the new rafters with either wood fibre or wool between the rafters.
The walls (about 600mm thick) will have all the cement render/ plaster and pointing hacked off and re plastered with Lime. I may also fix wood fibre board internally.
With the floor, I would like to insulate the floor and have UFH and am prepared to break up the existing concrete to lay new floors but have read conflicting advice on how to proceed.
Some claim that an old stone building should have a breathable floor so that moisture from the ground is not pushed into the walls.
Whereas elsewhere i have read that a modern floor (DPM, insulation & concrete) will be better as it prevents water vapour entering from the ground through the floor which will create internal humidity.
I am far from an expert on the matter and am seeking to learn more. If anyone has experience in this area I would appreciate all comments. Thank you
snowandrocks said:
Fitting underfloor heating to a breathable floor slab with no damp proof course sounds potentially disastrous to me.
The subsoil beneath your house is an effectively unlimited source of moisture which is free to reach the surface of your new floor, where it'll then evaporate off.
Heating this surface will speed up that evaporation dramatically, the floor will probably feel dry to the touch but will be pumping lots of water vapour into the interior of your cottage.
My recommendation would be to avoid trying to make your floor breathable - if you're worried about moisture levels in the external walls, lower the external ground levels where possible, even dig French drains around the base of the walls if it's really wet. Then keep the place well ventilated and well heated.
Yes, I've read this elsewhere on the Interwebs. The subsoil beneath your house is an effectively unlimited source of moisture which is free to reach the surface of your new floor, where it'll then evaporate off.
Heating this surface will speed up that evaporation dramatically, the floor will probably feel dry to the touch but will be pumping lots of water vapour into the interior of your cottage.
My recommendation would be to avoid trying to make your floor breathable - if you're worried about moisture levels in the external walls, lower the external ground levels where possible, even dig French drains around the base of the walls if it's really wet. Then keep the place well ventilated and well heated.
I'm basically trying to understand which is the less damaging side effect, go with a breathable floor but suffer the water vapour or go with a dpm and risk pushing moisture to the walls.
And obviously, being a layman, i'm simply parroting what i've heard/ read about these options....
So dpm, insulation, concrete slab is less potential risk, particularly if i make sure the external ground is lower/ drained?
I think what was clouding things for me regarding the breathable floor is that if the roof and walls are breathable then the vapour from the floor is sent out through those areas.
I think what was clouding things for me regarding the breathable floor is that if the roof and walls are breathable then the vapour from the floor is sent out through those areas.
Equus,
It was actually a post of yours on an earlier thread i came across that set me questioning the breathable floor idea.
And I’d originally started thinking about breathable floor slabs after watching You Tube videos of Peter Ward from Heritage House investigate old houses where he states that moisture can be pushed into the walls and that everything should be breathable.
May i ask, how did you arrive at this opinion?
My house is very cold. And even now, in the wet and cold climate of North Wales, it feels colder inside that out. The builders currently working on the job have commented several times that its warmer outside!
So i am seeking to improve things by 1-making it as breathable as possible (hacked off all the cement render inside and out) and 2- insulate as best i can with breathable materials (woodfibre in the roof and maybe wood panelling inside walls).
It was actually a post of yours on an earlier thread i came across that set me questioning the breathable floor idea.
And I’d originally started thinking about breathable floor slabs after watching You Tube videos of Peter Ward from Heritage House investigate old houses where he states that moisture can be pushed into the walls and that everything should be breathable.
May i ask, how did you arrive at this opinion?
My house is very cold. And even now, in the wet and cold climate of North Wales, it feels colder inside that out. The builders currently working on the job have commented several times that its warmer outside!
So i am seeking to improve things by 1-making it as breathable as possible (hacked off all the cement render inside and out) and 2- insulate as best i can with breathable materials (woodfibre in the roof and maybe wood panelling inside walls).
Equus said:
The guy is a (very convincing) charlatan with a (very large) axe to grind. He has no real background, training or education in building technology.
There is a grain of truth behind his obsession - certainly, rising damp is over-diagnosed and there are a lot of cowboys in the damp-proofing industry - but he's developed it into a fixation that goes well beyond anything that can be supported by either the science or practical experience.
His website should be read with the same degree of skepticism you'd reserve for any other conspiracy theorist.
What about his opinions on making the walls and roof breathable? There is a grain of truth behind his obsession - certainly, rising damp is over-diagnosed and there are a lot of cowboys in the damp-proofing industry - but he's developed it into a fixation that goes well beyond anything that can be supported by either the science or practical experience.
His website should be read with the same degree of skepticism you'd reserve for any other conspiracy theorist.
I've already hacked off the render, so I hope that wasnt a waste of time! And i'm planning to cover the roof with wood fibre sarking plus woodfibre (or maybe wool) between the rafters. But that is pretty expensive
C Lee Farquar said:
I've used woodfibre fairly extensively, I have an unfounded dislike of plasterboard. It is good stuff, very fire resistant, but it does expand considerably if it gets damp, which might have a bearing if your roof isn't completely water tight.
The roof is being completely redone, slates, timbers etc so at what its costing me it bl**dy well should be watertight....Just a quick follow up regarding the underfloor heating.
So the floor build up will go:
1. hardcore
2. sand blinding
3. dpm
4. concrete slab
5. insulation
6. screed with UFH pipes
Which is better, having the insulation above or below the concrete slab?
And, any suggestions for floor insulation,? I've read Kingspan is very good.
thanks
So the floor build up will go:
1. hardcore
2. sand blinding
3. dpm
4. concrete slab
5. insulation
6. screed with UFH pipes
Which is better, having the insulation above or below the concrete slab?
And, any suggestions for floor insulation,? I've read Kingspan is very good.
thanks
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