Insulating solid stone barn inside

[Some bloak]

Hello everyone

I'm just at the beginning stages of building a workshop in a stone outbuilding- my first proper workshop in fact. These old stone buildings have plenty of character but are incredibly cold to try and work in during winter. Anyway, my first major task is to internally insulate the whole thing, walls, roof, floor, door and windows. I've read about so many methods of insulation I'm fairly set on what materials I intend to use and what my budget allows.

What I intend to do is to cover the walls and floor in a 3 x 2 stud frame/ batten and then insulate the whole lot with 50mm Celotex before top cladding everything in OSB and 22mm chipboard for the floor. However, Is it better to go over the top of all the battening with the Celotex boards, tape the joints etc. or cut the boards to wedge fit inside the 600mm centres?. Without getting into mass thicknessing, 50mm insulation doesn't match up with the 3 x 2 thickness anyway.

I tend to think the better way would be to cover the stud work and try to completely isolate the cold walls rather than wedge insulation between which would surely create thermal bridging all over the place by having the 3 x 2's exposed. I would probably also use a DPM sheet up the walls as well as the floor just to keep any moisture in the walls back as much as possible.

If anyone's got any opinions or ideas I'd be very happy to hear any as there's alot of work in doing all this and I'm keen to get it right. Many thanks for anything that comes back from anyone, much appreciated.

 

[Beau]

Hi

Went through this for our house which is a barn conversion. The potentially biggest issue is moisture coming through the walls. On our most exposed wall water would end up running down the inside in extreme weather. You mention a DPM up the wall but can you attach your 3x2 stud to the roof or do you need to fix to walls? If you need to fix to the walls you will puncture the DPM. Also by fitting a DPM to the wall any moisture that does come through can't easily evaporate and will probably run down to the floor. Presuming you can resolve these potential problems I would insulate between and over your stud walls as I have yet to meet anyone who said they had over insulate their workshop or house haha. If your trying to keep costs down use glass batts in the studs and PU foam over top to avoid the thermal bridging.

 

[Some bloak]

Hi

Went through this for our house which is a barn conversion. The potentially biggest issue is moisture coming through the walls. On our most exposed wall water would end up running down the inside in extreme weather. You mention a DPM up the wall but can you attach your 3x2 stud to the roof or do you need to fix to walls? If you need to fix to the walls you will puncture the DPM. Also by fitting a DPM to the wall any moisture that does come through can't easily evaporate and will probably run down to the floor. Presuming you can resolve these potential problems I would insulate between and over your stud walls as I have yet to meet anyone who said they had over insulate their workshop or house haha. If your trying to keep costs down use glass batts in the studs and PU foam over top to avoid the thermal bridging.

Thanks for the reply. I was thinking about just the bare framework which would be fixed directly onto the walls. The timber would be treated. I would then just cover the entire frame with the DPM, then the 50mm Celotex. I know the DPM would get punctured here and there when I ultimately fix the OSB to everything but any moisture would have a fair bit of travelling through that lot to cause any big problems. What are the 'glass batts' you propose using?.

 

[Beau]

So your DPM is outside of the wooden frame. If water is coming through your walls the wood is going to be sitting in a very damp environment and unable to breath. I should add I am paranoid about water living on an exposed site on Dartmoor and you may well live in far less harsh environment. Just checked on the "batts" and I am getting muddled between jobs. Looks like the term batts is only used for the denser fibre glass rolls that are used for sound insulation. I just mean glass fibre that is firm enough to be pushed between upright frames without slumping. I should add I am no expert in these matters just a self builder. I found Green building forum is a great place to get advise on all things insulation related.

 

[Phil Pascoe]

You may well do better with microporous material like Tyvek rather than attempt a barrier with DPM. Someone more qualified to comment will be along soon.

 

[CHJ]

You need to keep a gap or substantial damp proof membrane between the wood studding and the wet wall, it will take only a matter of hours for penetrating water to wick through or across any timber in contact.

I have no idea what modern materials are available or used but many years ago when doing this to a farm building we used bitumen based DPC as used when building brick walls this gave a 4" (100mm) wide barrier with 2 X 4 studding centralised edge on fitted with galvanised clout nails to timber before assembly in case wood came into contact with the brick wall, frames were anchored top and bottom taking care to coat fixing positions with mastic so that barrier remained intact.

On the most exposed wall there were vents at the base to allow cavity air flow up into the vented roof space.
Insulation was compressed 2" straw slabs between the timbers with spacing blocks to stop it falling back against wall, (stramit?) with a plywood skin.

All very high tech. at the time, many of the new buildings/sheds were just single skin cement asbestos sheet.

 

[Selwyn]

how about insualting outside and rendering?

 

[Woody2Shoes]

Hi - I think that the batten space on the cold side of the insulation probably needs to be ventilated, and that you need a vapour-impermeable barrier on the warm side of the insulation. You have two sources of moisture: A - the old floor and walls, which are cold and B - you on the inside, which is warm. Have a Google for "Interstitial condensation". Cheers, W2S

 

[RobinBHM]

How uneven are the walls? -could you do the 50mm insulation first as a continuous layer, then fix 3 x 2 flat against the insulation?

I would avoid putting the timber on the damp side, it will suffer from both damp and condensation.

You could tank the wall with an SBR slurry (cement + SBR), which is a cheap way to apply a tanking and will hold back a fair water pressure.

 

[Tonytygwyn]

Just went through each same process the building inspector on my job recommended an air gap of 50mm between the stone walls and the internal studding with 50mm celotex between studs. Any water would run down the stone walls and then below the concrete slab (with DPM) which was left short of the walls by the same gap.

 

[Some bloak]

Just went through each same process the building inspector on my job recommended an air gap of 50mm between the stone walls and the internal studding with 50mm celotex between studs. Any water would run down the stone walls and then below the concrete slab (with DPM) which was left short of the walls by the same gap.

What will you use to fix against the wall to give you the 50mm gap without creating any damp bridging from the wall. Or maybe the room allows good top and bottom fixing points?.

 

[Beau]

We took an unconventional approach but it has worked very well. First we tanked the wall with DPM like this http://www.deltamembranes.com/products/ ... -membrane/. The tanking is set in bellow our floor slab to an underground drain. Then fixed back 2"x1" batten to it with these which allowed adjustment for the unevenness of the walls http://www.hafele.co.uk/shop/p/adjustab ... 27952/6622. The screws go into brick plugs that seal against the tanking http://www.deltamembranes.com/products/ ... -grommets/. Then used a multifoil insulation which is stapled to the batten. All the joins in the foil need carful taping. Then another 2"x1" batten which runs the opposite way to the first batten. Then fixed our internal lining to the inner batten. What you end up with is a completely watertight wall with high levels of insulation in minimal thickness. BCO took some time to think about it but signed it off. There has been some debate online about the effectiveness of multifoil insulation but to my mind it is great stuff if installed as recommended.

 

[Some bloak]

I've pretty much decided which way to go with the insulation order of things. I intend to put a heavy duty DPM sheet against the (stone) wall. Then build the stud wall/battening on top of that, and where any fixings penetrate the DPM I'll make good with some silicone at those points.

My main question; is there any reason why I can't cover the whole stud frame with the Celotex sheets and foil tape all the joins?. This would save all the laborious cutting and wedging of the insulation between the stud work. Presumably would also cut out any thermal bridging through the studs than if I was fixing between them.

I would then clad the whole lot inside with 18mm OSB, fixing the boards through the 50mm Celotex onto the stud work behind.
Does anyone envisage any problems in this method?. Thanks for all help and advice.

 

[Beau]

Other than the possible problems mentioned with the moisture behind the DPM having nowhere to go the rest of build sounds good. An 18mm OSB wall is great for fixing too but be aware that OSB used to be cut to imperial sizes (this was a few years back) and the Celotex will be metric so widths of the sheet may well differ.