Insulating an old, stone built house

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Paddy86
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Insulating an old, stone built house

Post by Paddy86 » Mon 11th Oct, 2021 10:34 am

Hi all

Been following a number of threads on here for a while but thought it was finally time to ask my own questions.

My wife and I moved into a stone built ex vicarage from circa 1890. It is up on the banks of the Tyne valley so gets a little nippy in the winter and we are keen to do what we can to improve the thermal properties of the walls. We are planning a bit of a test in a new bathroom we are building as the plaster is damp in one area (leaking gutter above - getting fixed) and we are going to have to strip it back and replaster. We have managed to find a local company who have experience with lime plaster but says he just uses hemp to improve insulation. Having done some looking online I have seen all sorts of other products that seem to build in more insulation which still maintaining their lime plaster breathability.

Does anyone have any experience with which products perform best? I have seen Ultra, Wormseley and Bauwer products advertised quite heavily.

Also, because we are tampering with the external walls I am thinking we will have to get building regs involved, any tips for getting their sign off when the U value is unlikely to hit 0.3?

Thanks in advance.

Paddy

Zebra
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Location: St Albans, Hertfordshire

Re: Insulating an old, stone built house

Post by Zebra » Wed 13th Oct, 2021 5:20 pm

Hello Paddy86, welcome to the forum.

Obviously external wall insulation is better than internal, as then the wall itself is on the warm side, but this is likely impossible on a stone built house, at least without drastic changes to the appearance. So internal it is. I have used lime hemp mainly for ceilings, it's nice stuff to use but its not very insulating as you said. The system that I went for to seemingly good effect is woodfibre internal wall insulation. Pavatherm I think was the brand. It's more insulating than lime hemp for the same thickness, you fix it to the wall and you then lime plaster over the top.

In terms of building control, I confess that if it were me I might not bother. I suppose it depends if you are thinking of selling any time soon and will need all your paperwork in order....I had to knock down and rebuild two areas of the house, for which I put in building notices as if they were new extensions. When the building control officers came to look, they glanced over at what I was doing to the old parts of the house, said with interest "oh, you're using that are you?" but didn't mind that I hadn't declared it. I emailed the Building Control officer, who emailed me back to say that although the current U value requirement is 0.28w/m2K, due to the age of the property I should aim for 0.35w/m2k and that if I put in an application they would enforce it (implying that if I didn't, they wouldn't...... so I haven't).......

paulc
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Re: Insulating an old, stone built house

Post by paulc » Thu 14th Oct, 2021 1:23 pm

Paddy86 wrote:
Mon 11th Oct, 2021 10:34 am
Also, because we are tampering with the external walls I am thinking we will have to get building regs involved, any tips for getting their sign off when the U value is unlikely to hit 0.3?
Unless you are doing more than 25% of the total exterior wall area, no need to involve building control. I'm refurbishing one room at a time and insulating the walls. This keeps me well under the 25% rule and I'm comfortable with not involving building control (also saves a few pounds on their fees).
Hemp plaster as an insulator - You have to put on a really thick layer to get any benefit. A work colleague used the stuff in her cottage and is far from impressed with the results.

worms
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Re: Insulating an old, stone built house

Post by worms » Fri 15th Oct, 2021 9:30 am

While I love the idea of good, breathable insulation made of natural products, I'm afraid that when I insulated my bathroom (DIY) I went for simplicity and readily available materials. House is a 1940s conversion of a 1870s barn, built of rubble-stone.

I took the old plaster board off and built a new internal stud wall with an air gap between the stone and the stud. The new internal wall comprised an outer layer of foil-backed bubble wrap, 100mm Kingspan (it was actually 1x50mm and 2x25mm because of local availability of small boards) then faced with Gyproc above dado level and pine boards below. The end result is that I lost about 125mm off the length of the bathroom, but the stone wall still breathes along its length behind the new studwork, without having to cope with the additional humidity of a bathroom. The internal wall is much warmer and a previous condensation problem is eliminated. Despite moving everything, including the toilet, four inches forward, I managed to DIY this while my wife was away, and having repainted it all exactly as it was, the only thing she noticed was the new toilet seat!

a twig
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Re: Insulating an old, stone built house

Post by a twig » Fri 15th Oct, 2021 6:27 pm

paulc wrote:
Thu 14th Oct, 2021 1:23 pm
Paddy86 wrote:
Mon 11th Oct, 2021 10:34 am
Also, because we are tampering with the external walls I am thinking we will have to get building regs involved, any tips for getting their sign off when the U value is unlikely to hit 0.3?
Unless you are doing more than 25% of the total exterior wall area, no need to involve building control. I'm refurbishing one room at a time and insulating the walls. This keeps me well under the 25% rule and I'm comfortable with not involving building control (also saves a few pounds on their fees).
Hemp plaster as an insulator - You have to put on a really thick layer to get any benefit. A work colleague used the stuff in her cottage and is far from impressed with the results.
Just to be contrary we had great results in with hemp plaster in our place, and if you buy it premixed it’s classed as an insulation product so it attracts lower VAT

Where we didn’t do that, we did wood wool boards with NHL skim to good effect

Lacan07
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Re: Insulating an old, stone built house

Post by Lacan07 » Tue 19th Oct, 2021 1:38 pm

I agree with Paul, I wouldn't involve building control unless you're stripping multiple walls of the original plaster. My building control was happy with me using 60mm of Wood fibre board, they should show some understanding of the fact its a solid brick wall that needs some heat to get through.

Wood fibre board seems to be the most commonly used product for IWI, but bear in mind your substrate will have to be flat. There shouldn't be any gaps behind. Although I think 'Back to Earth' do a wood fibre product that you can use straight on to uneven walls.

I've used Lime Green 'Ultra' plaster before for various things. Its great for filling in gaps, etc around windows, and for patching holes in lathe and plaster walls. But I wouldn't be so confident using it as a base coat to float out a wall, and I doubt a professional would appreciate being asked to use it either. To be blunt it goes off like a bitch, into something resembling a cheese cake biscuit base. Obviously the room temperature plays a large part, but I find you have to cut it pretty soon after its applied to get it flat. Its a shame because I love the concept of an insulating plaster and when you put your hand on it you can feel the difference it makes.

a twig
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Re: Insulating an old, stone built house

Post by a twig » Tue 19th Oct, 2021 10:31 pm

Lacan07 wrote:
Tue 19th Oct, 2021 1:38 pm
Wood fibre board seems to be the most commonly used product for IWI, but bear in mind your substrate will have to be flat. There shouldn't be any gaps behind. Although I think 'Back to Earth' do a wood fibre product that you can use straight on to uneven walls.
Again I’m going to disagree I’m afraid :) fixed ours directly onto a rubble stone wall and got great results, as I think have others on here, don’t let the perfect be the enemy of the good

Zebra
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Location: St Albans, Hertfordshire

Re: Insulating an old, stone built house

Post by Zebra » Wed 20th Oct, 2021 12:04 pm

I pre-flattened with a coat of lime plaster.....you could even pre-flatten with a bit of lime hemp...

CliffordPope
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Re: Insulating an old, stone built house

Post by CliffordPope » Wed 20th Oct, 2021 6:15 pm

Zebra wrote:
Wed 13th Oct, 2021 5:20 pm
Hello Paddy86, welcome to the forum.

Obviously external wall insulation is better than internal, as then the wall itself is on the warm side, but this is likely impossible on a stone built house, at least without drastic changes to the appearance. So internal it is.
It's a dilema either way.
External would completely destroy the outside character of the house.

Internal insulation however would require massive (and very expensive) modifications to all the wooden door, window and skirting mouldings, and replacing plaster coving in all rooms. I'm not sure what would happen around original fire places and mantle pieces - they would certainly look odd if now recessed inside a new wall lining. Can a marble fire surround be removed undamaged and refitted on top of the insulation? Can a tall mantle piece be re-hung on a battened wall?
What happens to wooden panelling in the window embrasures?
What do you do with cupboards recessed inside walls?
How do you line a bathroom if there is only a very small clearance at each end of the roll-top bath?
What do you do about all the countless things attached to walls - bookshelves, pipes, light switches, sockets etc?
How do you insulate a sloping attic ceiling if there is already limited headroom?

Zebra
Posts: 2637
Joined: Sun 1st May, 2011 10:42 pm
Location: St Albans, Hertfordshire

Re: Insulating an old, stone built house

Post by Zebra » Mon 25th Oct, 2021 4:00 pm

CliffordPope wrote:
Wed 20th Oct, 2021 6:15 pm
Zebra wrote:
Wed 13th Oct, 2021 5:20 pm
Hello Paddy86, welcome to the forum.

Obviously external wall insulation is better than internal, as then the wall itself is on the warm side, but this is likely impossible on a stone built house, at least without drastic changes to the appearance. So internal it is.
It's a dilema either way.
External would completely destroy the outside character of the house.

Internal insulation however would require massive (and very expensive) modifications to all the wooden door, window and skirting mouldings, and replacing plaster coving in all rooms. I'm not sure what would happen around original fire places and mantle pieces - they would certainly look odd if now recessed inside a new wall lining. Can a marble fire surround be removed undamaged and refitted on top of the insulation? Can a tall mantle piece be re-hung on a battened wall?
What happens to wooden panelling in the window embrasures?
What do you do with cupboards recessed inside walls?
How do you line a bathroom if there is only a very small clearance at each end of the roll-top bath?
What do you do about all the countless things attached to walls - bookshelves, pipes, light switches, sockets etc?
How do you insulate a sloping attic ceiling if there is already limited headroom?
Indeed, those would all give definite cause for concern. Luckily for me, or not so lucky depending on how you look at it, my internals had all been modernised in the 60s so nothing to save.

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