Solid wall insulation

Harl0

Harl0

Harl0

Associate
Joined
23 Oct 2012
Posts
213
Hi all

I live in a property of sandstone construction originally built in 1894 and extended (using sandstone) in 1990. As far as we know none of the walls have any internal or external insulation applied.

In a bid to improve our heat retention I have been researching our options. I am targeting our dining room and hallway first which are the coldest rooms. At the moment I feel internal insulation is our best bet. I have looked at stripping all wallpaper/ paint and inspecting the plaster and removing if necessary.

Options
1/ Repair/ replace plaster where necessary and use calcium silicate board or wood fibre based products which can be applied directly to the wall
2/ Repair/ replace plaster where necessary and build a new stud wall creating a cavity and vapor barrier. The plaster board will either be insulated, or we fill the cavity with a suitable insulation.

Does anyone have experience with this or can provide any recommendations, please?

Thanks!
 
On the flip side... I'm literally removing all lath and plaster and rebuilding the walls :cry:

I hate lath and plaster so happy to get rid of it. Also means I get to keep my cornice without too much fuss. Great opportunity to rerun cables for sockets/network and move radiators as well.

I mean, not much advice to give. None of it is really "hard", just costs either your time or money to get someone else to do it. If you want to feel the most benefits get carpet though... We've done the same thing in two similar sized rooms and one has carpet, the other we've gone solid wood and what a difference a couple of good layers of insulation under your feet does to the "feel" of the room. Cold feet zap the heat out of you :(
 
I've not used it but heard good things about Wallrock thermal liner could be an option to test in one room before looking at other option.

In our current renovation we've done your option 2 to the original part of the house which was circa 150 year old stone wall filled with scalping's, we were gutting this part anyway as a few joists were rotting but opted to strip the house bare floor to roof and had a new timber frame built within. This gave us a 50-75mm cavity give or take with the shape of the walls followed by a 4x2 frame and lined both sides with 9mm OSB3, I then filled the frame with 90mm Knauf frametherm and regular plasterboard on the internal side, granted we dug the floor out and insulated it as well but the difference the walls made is amazing having lived in an identical house previously. My major concern was loss of space but we were also adding 100+m2 of living space in the extension so weighing it all up it was the option that won and now we've painted you'd never notice the loss or additional framework.
 
I'm looking into this too for an 1870s property

Just be sure to do plenty of research. I've read some horror stories of where adding insulation causes huge damp issues or structural issues.
 
Kill_Phil said:
I'm looking into this too for an 1870s property

Just be sure to do plenty of research. I've read some horror stories of where adding insulation causes huge damp issues or structural issues.
Click to expand...

This is another thing that swung us towards option 2 I posted above, we hacked all the old plaster off in the cavity to ensure it could breath properly and adding some vents front an back, coupled with the attic vents keeps the cavity lovely and dry. I'd also read of the horrors of internal or external insulation on stone houses.
 
Thanks for the feedback.

At the moment option two is looking to be the way forward.

I contacted Kingspan about their internal insulation products - They recommended their Kooltherm K118 in 62.5mm thickness based my sandstone being approx 30cm thick - https://ks-kentico-prod-cdn-endpoin...Original/48490_ProductBrochure_K118_01_UK.pdf

If you scroll to page 3 you can see the basic install instructions for solid stone walls - which seems the same approach as you are taking @SoliD

This is the downstairs floor plan focusing on the dining room and hallway:
https://drive.google.com/file/d/1V6fOJjmSz2NWDqWmM8KvOgGdH68AjIG6/view?usp=sharing
view


Key for lines:
Purple - Radiators
Green - Add internal insulation
Yellow - Power sockets

@SoliD I was wondering if you can tell me what thickness batons you are using and if you are using a vapor barrier, please?
 
Last edited:
Hi Harlo, got 47mmx50mm from my local merchant and yes vapor barrier will be going in along expanding foam and foil tape. Going full belt and braces.
 
I've also a sandstone house of similar age (~1860s). Keeping it warm seems pointless and I have ~60cm walls :(

Just sharing what I've been reading into, so don't quote me entirely, but sandstone walls needs to breathe and I keep reading this means you shouldn't be using gypsum plaster as it will trap moisture in the wall and you'll get damp. You need to be using lime plaster, which from what I read is a much more skilled and expensive job to get done. I think the conciousness was using gypsum for internal walls was OK though.

The same goes for whatever insulation you look at as well- it needs to be breathable to let moisture through and I assume any vapour barriers too.

If you want to paint the wall that's another potential issue as well; normal Johnston's/Dulux vinyl etc paints aren't breathable (maybe they do have some that are). And so again more expensive but I read that Earth Born Paints are meant to be pretty good and are breathable.

Just did a quick bit of Googling and https://selfbuildcouple.com/types-of-wall-insulation-for-a-stone-house/ seems to cover quite a few of the options quite nicely.

The stud wall and dry line option seems very appealing if it would allow you to finish with normal (gypsum) plaster, normal insulation, normal paints etc. That would make things so much less hassle.

Every time I look into this the whole thing seems like a massive headache. Eager to find out what you end up with so I can look at copying :D
 
It’s a minefield of information and there doesn’t actually seem to be a right answer out there. Amusingly before I read any of this stuff we replastered our Victorian solid brick house with modern plaster and repointed loads of it with sand and cement which oddly in over a decade has cause no damp or damaged bricks contradicting everything you will read online. I think the real truth is your kill age will vary massively and it is best to be cautious, we have just bought a new house which is a mixture of dressed stone and brick which someone has previously repointed in patches with sand and cement causing some of the stone work to blow!
 
SoliD said:
Hi Harlo, got 47mmx50mm from my local merchant and yes vapor barrier will be going in along expanding foam and foil tape. Going full belt and braces.
Click to expand...

Thanks for the info.

I guess the process for solid stone would be:
1/ strip plaster to expose the bare stone
2/ once any damp areas have dried, attach the batons to the stone work forming the frame
3/ attach vapour barrier to insulation boards which then slot into the frame?
4/ attach plaster board to batons
5/ tape seams
6/ skim boards
7/ paint

I wonder what happens if your stonework isnt plumb and you end up with a wonky frame - This is a new field for me so apologies if this is incorrect :)
 
Pho said:
I've also a sandstone house of similar age (~1860s). Keeping it warm seems pointless and I have ~60cm walls :(

Just sharing what I've been reading into, so don't quote me entirely, but sandstone walls needs to breathe and I keep reading this means you shouldn't be using gypsum plaster as it will trap moisture in the wall and you'll get damp. You need to be using lime plaster, which from what I read is a much more skilled and expensive job to get done. I think the conciousness was using gypsum for internal walls was OK though.

The same goes for whatever insulation you look at as well- it needs to be breathable to let moisture through and I assume any vapour barriers too.

If you want to paint the wall that's another potential issue as well; normal Johnston's/Dulux vinyl etc paints aren't breathable (maybe they do have some that are). And so again more expensive but I read that Earth Born Paints are meant to be pretty good and are breathable.

Just did a quick bit of Googling and https://selfbuildcouple.com/types-of-wall-insulation-for-a-stone-house/ seems to cover quite a few of the options quite nicely.

The stud wall and dry line option seems very appealing if it would allow you to finish with normal (gypsum) plaster, normal insulation, normal paints etc. That would make things so much less hassle.

Every time I look into this the whole thing seems like a massive headache. Eager to find out what you end up with so I can look at copying :D
Click to expand...

Thanks for sharing this! Just had a read through. Intrigued by the Hemp Wool. Seems easy enough and ticks the breathability box - guess you wont need a vapour barrier in this use case just use any kind of plasterboard providing it isn't foil backed.
 
Harl0 said:
Thanks for the info.

I guess the process for solid stone would be:
1/ strip plaster to expose the bare stone
2/ once any damp areas have dried, attach the batons to the stone work forming the frame
3/ attach vapour barrier to insulation boards which then slot into the frame?
4/ attach plaster board to batons
5/ tape seams
6/ skim boards
7/ paint

I wonder what happens if your stonework isnt plumb and you end up with a wonky frame - This is a new field for me so apologies if this is incorrect :)
Click to expand...

I'll try to dig out the website that showed the different ways of doing it really simply!, but you've got a few steps mixed up there.
 
SoliD said:
@Harl0 https://www.insulationsuperstore.co...ion/how-to-install-celotex-insulation-boards/ this is a great guide to how to do stuff and in what order. This is another one that may be of use. https://insulation4less.co.uk/blogs/guides-and-news/how-to-insulate-an-old-cottage

Did find another point that says you don't need a vapour barrier if the insulation you buy has one installed already (ie Celotex) you'll just need to tape the joins which is what I suspect i'll do.
Click to expand...

Ahh this is really helpful!

In your example, where are you applying the tape for the joins - is this any point you have to join any Cleotex boards, or taping the gaps between the batons and the boards?
 
Tape will go around the edges of the celotex boards and the batons. Any gaps between board and baton will be filled with expanding foam too. Should get some photos tomorrow as hoping to finish the majority of that room.
 
You must log in or register to reply here.
Back
Top Bottom