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Insulating a wooden shed / workshop


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I've explicitly banned the beach-hut painting ideas as I don't really want to advertise to any local thieves - keeping it looking like a big shed rather than a posh "Garden Office" or "Summerhouse" or whatever will hopefully draw less interest.

Given the frame of the shed is 3x2 and the insulation is 50mm I've been advised that the thing to do is to put battens against the outer wall to create an air gap, then plastic sheet, then the insulation.

Or maybe air gap, insulation, then plastic sheet as Soren's post suggests...

Floor-wise I've bought some wood preserver with lots of warnings about killing dolphins (this is the best way to rate surface treatments - the more harmful to the environment, the more effective it is) so I'll slosh that about first. After that, the plan is to put a sheet of DPM down, then insulation board, then floor board. That flooring Nige found looks good, although it reminded me I have some decent carpet tiles stashed somewhere which might be enough to do it...

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If you use 5 lever locks on the door, if the insurance company you use is like the one we do, then the contents of the "workshop" may be covered under your house contents insurance.

Just call them and make sure.

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Breatheable membrane between insulation is OK - AS long as you have a moisture proof barrier on the inside of the insulation.

You want to control the moisture from inside of the building e.i. Breathing, farting, sleeping, boiling water and what have you got.

This moisture is to be keept away from the insulation in ordre for it not to condensate and stay in the insulation and framework = rot !

The moisture trapped inside the building si to be let out by controlled venting e.i. leggy vents or open doors and windows. If this is your house (which its not in this case) then the best way to vent via windows and doors are 4 times a day as open as posible and for 5 min. periods at the time. Fresh data from the Energi dept.

The barrier on the outside of the insulation is to stop the wind to blow through the insulation and be cooling this way. This barrier will also do as a water barrier if any should get throu the outer surface.

When here in Denmark this is the ordre of constructing for wooden buildings.

From inside and out.

Plaster (or other) - dampproof barrier, glued taped and whta have you - insulation (this is placed in the wooden structure) - windbarrier - 25 mm. airgab - outer surface.

The dampproof barrier can be placed up to a third in to the insulation, from the INSIDE, this will alove for cables to be mounted/hidden without breaking the barrier !

Well not very LR-related, but ought to clear a few things.

Morten

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Ah, so the moisture barrier is to protect the structure from internally generated moisture?

And the breathable barrier prevents mould, and the like, in the insulation?

It becomes clearer now.

G.

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Weird !

After I have been replying to this thread, I have recieved 3 phonecalls and 1 mail from the UK regarding surveys in building bla bla bla ?

Thought we were pretty "safe" here ?

Happened to anybody else or is this just a coincidense ?

Morten - from Denmark

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Fridge,

I converted an outhouse into an office, was single skin brickwork from 1947, and fixed this stuff to it, in 40mm guise:

http://www.celotex.co.uk/products/celotex-products/celotex-pl4000

Bloody fantastic, and fitting is a dream, the bonus is you get the 12mm plasterboard thrown in, so saves on fitting time vs insulation and then putting plasterboard on top and forgetting where your battens are...

Skip to 3:26.

Any good builder merchants should be able to get it, easier as you don't have to buy a whole pack as most places do it...

Yes you want an air gap, I suppose in total I lost 75mm space from each wall, but the office is toasty warm even with only a small electric convection heater (fan heaters make too much noise!)

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A bit late for anybody who has already built one but...

FWIW I have just built a garage and an extension in the last 18 months, in about the windiest spot you could imagine. We also have a tongue and groove garden shed and it leaks like a sieve, insulating it would be a complete waste of time as the inside is always damp and it would rot.

The best construction method IMHO is to frame it yourself, it really isn't hard and the only tools you need are basic woodworking tools plus a circular saw, decent 18-24v drill and preferably a mitre/chop saw.

Build the framing out of 2x4 timber, with OSB ply (9mm structural, though I used 11mm due to the wind) nailed to the outside of the frame. Overlay that on the outside with a breather membrane (Tyvek or similar for walls, roofing felt on roof) and then battens (19x38mm) and the preferred cladding - though if done properly it will be completely waterproof once the paper is on. Mine is clad (both walls and roof) with 2x3 purlins and profiled steel sheeting screwed to that with roofing screws. The extension we're just building is done with Cedral cement weatherboard.

The materials for my 12 metre long x 9 metre wide x 3.4m wall height garage (bigger than the house, as my wife reminds me regularly...) came to about £12000 IIRC, plus another £4k for the concrete floor and £3k for the roller doors (2.8x3.0m industrial doors). Two of us built it and the only assistance needed was standing up the wall panels and putting the A frames on the roof, which are 5.7m to the apex - done by 3 of us and the winch on my 110.

You could build a 'normal' sized shed for peanuts - it was much cheaper than the steel framed farm building I looked at as an alternative, and much warmer. Apart from around the roller doors it's completely draughtproof and damp proof.

Insulating the above construction method is a doddle - stuff 100mm rockwool in the wall cavities and board over the inside with plasterboard or whatever you want. Put a ceiling in and put rockwool on top of the ceiling. I haven't done the garage (no need - 30kw space heater keeps it warm enough and the roller doors are inherently drafty making efficient insulation elsewhere a waste of time) but it would be easy to make it as warm as a modern house.

Some time I might do a more detailed build post with photos - if that would be of interest? The building methods can be applied to anything from a small garden shed to something the size of what I did last year.

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A bit late for anybody who has already built one but...

FWIW I have just built a garage and an extension in the last 18 months, in about the windiest spot you could imagine. We also have a tongue and groove garden shed and it leaks like a sieve, insulating it would be a complete waste of time as the inside is always damp and it would rot.

The best construction method IMHO is to frame it yourself, it really isn't hard and the only tools you need are basic woodworking tools plus a circular saw, decent 18-24v drill and preferably a mitre/chop saw.

Build the framing out of 2x4 timber, with OSB ply (9mm structural, though I used 11mm due to the wind) nailed to the outside of the frame. Overlay that on the outside with a breather membrane (Tyvek or similar for walls, roofing felt on roof) and then battens (19x38mm) and the preferred cladding - though if done properly it will be completely waterproof once the paper is on. Mine is clad (both walls and roof) with 2x3 purlins and profiled steel sheeting screwed to that with roofing screws. The extension we're just building is done with Cedral cement weatherboard.

The materials for my 12 metre long x 9 metre wide x 3.4m wall height garage (bigger than the house, as my wife reminds me regularly...) came to about £12000 IIRC, plus another £4k for the concrete floor and £3k for the roller doors (2.8x3.0m industrial doors). Two of us built it and the only assistance needed was standing up the wall panels and putting the A frames on the roof, which are 5.7m to the apex - done by 3 of us and the winch on my 110.

You could build a 'normal' sized shed for peanuts - it was much cheaper than the steel framed farm building I looked at as an alternative, and much warmer. Apart from around the roller doors it's completely draughtproof and damp proof.

Insulating the above construction method is a doddle - stuff 100mm rockwool in the wall cavities and board over the inside with plasterboard or whatever you want. Put a ceiling in and put rockwool on top of the ceiling. I haven't done the garage (no need - 30kw space heater keeps it warm enough and the roller doors are inherently drafty making efficient insulation elsewhere a waste of time) but it would be easy to make it as warm as a modern house.

Some time I might do a more detailed build post with photos - if that would be of interest? The building methods can be applied to anything from a small garden shed to something the size of what I did last year.

Definitely interested to see a build thread :). I follow quite a few on Garage Journal forum.

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  • 1 year later...

My new workshop came with the breathable membrane already fixed to the outside of the timber studs with half round T&G cladding directly on top (no air gap).

I'm planning on boarding out the inside with 11mm OSB but am now confused about the insulation. :blink:

If I put celotex/Rockwool in the gap then it will sit on top of the membrane. Is this OK?

If I use Rockwool etc then I need a plastic vapour barrier over that before I board - is that correct?

Malcolm

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