insulating a shed

Hi All
I know this has been debated in the past but I am damned if I can remember the final verdict (if there ever was one!)
I have a 10 foot by 8 foot tongue and groove shed which I am siting on a concrete slab.
I intend to insulate it with either Crown Wool or Dry Therm - I can easily build up the sheds battening to accomodate a decent thickness of either. My inclination at the moment is to go with 75mm dry therm cut to fit. The inner skin would be 4mm hardboard nailed over the insulation
Question is ......... do I need a moisture barrier? I suspect I do, and should it go between the insulation and the outer skin of the shed or between the insulation and the inner skin. I would think it should be the former.
I was intending to use standard clear plastic dpm - which I will probably have left over from casting the concrete slab.
Not sure how to go about insulating the floor yet! It will be 12mm sterling board or ply on 4x2 'joists' which sit on the concrete.Its just possible that I could lay rows of bricks on top of the slab and sit the joists onto the bricks - to keep the damp out of the joists. I had thought about nailing a board - Something like a couple of strips of feather edge to close the open ends between the joists. Close enough to the ground to keep the mice out but would still allow some limited movement of air. I hope to give the underside of the shed a coat of bitumastic to help keep the damp out.
I have plans on how to deal with the windows (double glazing which I just happen to have and thick curtains) and the door (an insualted lobby with an outer door built onto the side of the shed, both doors draftproofed).
I know it sounds a bit belt and braces but I need to be able to store 'electrical stuff' in there that would be totally knackered in an ordinary shed. I have a (limited) power supply laid on and will have a tubular heater on a stat to stop the place freezing in winter. The cold isn't such a desperate problem as the combination of damp and cold.
It will also have the added bonus of being warm enough to sleep in when the wife locks me out :o)
All wisdom (on the insulation, not the wife) gratefully received!
regards
Dudley
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I insulated mine with 40mm Rockwool slabs and then lined the shed with polythene sheet stapled to the joists, works great in the summer as I used to boil working in it , its ok in the winter with a little 1kw fan heater , not noticed any damp problems
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Dudley wrote:

Some form of rigid insulation is the simplest to install. I used 50mm jablite on mine. Foil covered PIR foam would have been better still but I could not find it at a sensible price at the time. I did not bother with a vapour barrier myself.
> The inner skin would be 4mm hardboard nailed over the insulation
You might want to consider something a bit more substantial like 12mm ply since that will allow direct fixing of shelves and hooks etc without needing to find a stud all the time.

If I were using one, then I would put it under the exterior cladding.

I went with the joists on half bricks solution. Seems to work ok. I used 3/4" ply on the floor with no other insulation.
http://www.internode.ltd.uk/workshop/images/thebase.jpg

Treat all the wood that will be inaccessible with several coats of wood preserver. I found with the on bricks solution you can have a skirt that goes down to just below the top of the bricks. This allows air flow under the shed and looks neat.
http://www.internode.ltd.uk/workshop/images/outside.jpg

I have a small wall mounted fan heater which is left permanently switched on at its 800W setting. It is connected via normal room stat set to about 6 degrees. That seems more then enough to give frost and damp protection without it needing to fire up that often.
--
Cheers,

John.

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John Rumm wrote:

Mine has 70mm jablite on the walls covered with 12mm OSB. However, i've just found a source of plywood that was only a few quid more per sheet, so i'll be choosing this in preference for the rest of the walls when I get around to it ...

Hardboard will bow badly, I used 6mm ply as a maximum over the ceiling insulation, to cut down on weight the rafters are supporting. I also used Celotex up there, as it's more critical to have better insulation above. It also cuts down overall cost as they're about 2.5 X the cost of Jablite ...

My DPM is between the outside wall and the insulation.

Definitely do this.
I did this on all battens and boards, inside and out and used pressure treated wood over a DPC for the batten that was on the floor.
Cheers
Paul.
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Dudley wrote:

Stick it on piles - why bother with concrete?

I should use something more substantial than Sterling board... thick green Caberfloor would be far better than that.
which sit on the concrete.Its just

Sit them on pieces of DPC on the bricks.

I wouldn't rate your chances of success as more than a microsquidgeon above 0!

I shouldn't bother, it might even be counter-productive. If the shed bottom is a foot or so above ground, it will be fine.

*A SHED WITH CURTAINS*???
Good point about the draft-proofing, you wouldn't want a bunch of conscripts suddenly marching through with their muddy boots on..

Cut up Jablite and put it between your timbers. Put plastic DPM all over the inside, and fill with Sealofoam where necessary. Make sure detailing of your T&G is OK. What are you doing about the roof? Felt? Corrugated iron? Onduline (ptah!)?
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Celotex or Kingspan rigid boards are the best. They'll get much more insulation into a limited space. Indeed, it will probably save you the battening as you can insulate just between the panels.
I got mine from http://www.secondsandco.co.uk . I plasterboarded over and painted. Much more civilised than the average shed interior. It keeps the spiders away too.
Christian.
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I really dont want to go down the plasterboard route - its a real pain to get rid of the leftovers around here now that its classified as hazardous waste :o( Also Powys would be a fair way to go to collect or to have insulation delivered from - I am in Cambridgeshire.
I have decided to do the roof with 12mm sterling and roofing felt. I'll be putting a few extra strengthening gussets into the inside of the pitch. The roof insualtion will be 50mm polystyrene covered with hardboard.
On reflection 12mm sterling may be a bit twangy for the floor and I could spare an inch or two of height to put down some battens over the joists, put in some 25mm polystyrene board and then kitchen grade chipboard floor over the top - ought to stiffen things up!
I have some weld mesh I can put over the open ends of the floor joists/brick supports that ought to take the average mouse a while to get through! The feather edge can go over that as a 'decorative cover'.
The foil covered polystyrene insulation would be the easiest but also the most expensive solution and as this is all being done on a very tight budget - I think the thermal batts will be used, unless I come across a whole load of very cheap rockwool in the free ads or freecycle.
Cheapness is the reason for using hardboard as a liner. I can live with having to pick up studs to get shelf fixings etc, although varnished ply would be much more aesthetically pleasing!
Looks like best place for the moisture barrier is between the sheds outer skin and the insulation.
Thanks for the suggestions one and all.
regards
Dudley
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That's the first I've heard of it. At my local tip, you don't even have to queue, as it counts as hardcore which has a separate entrance.

They are effectively a national company.

It depends on how much insulation you need. Celotex/Kingspan is similar to polystyrene in terms of ease of use, but has better insulation qualities for the same thickness. Definitely get a quote though. You may find it not much more than the polystyrene you are considering.

Floor insulation isn't anywhere near as important as ceiling or wall, so I didn't bother.

I didn't bother with this either.
One thing I did do was paint the shed with proper exterior acrylic. It may look a little like a beach hut, but I find it much more aesthetically pleasing than the normal shed stains. It also protects better.
Christian.
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Christian McArdle wrote:

You may not have any restrictions at present but they will come. Some sites will have a special container for plaster based products and some will not take it at all.
I rang my local authority and they confirmed the changes. It seems that when plaster board gets wet and breaks down it releases ??
regards
Dudley
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wrote:

Exactly the same "toxic products" as it would in a house if it ever got wet. The council have their knickers in a twist - either that or everyone who ever got a plastered wall wet is about to die a horrible death.
Just send it round to Two Jags as a Christmas present.
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Didn't see earlier posts ... but why not use Foil faced PU ....... Seconds & Co will sell you sheets with dinged surface / corners much cheaper than new, and delivery anywhere in UK.

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Dudley Wrote:

I wouldnt put in a moisture barrier, its likely to trap moisture a much as stop it, the timber can breathe so leave it. Celotex/Kingspan is a lot easier to use than Jablite, it cuts much mor accurately and leaves a lot less mess. If you start cutting jablite yo wont believe how much "snow" you get. You could always float a ply floor on top of sheets of Celotex/Jablit and do away with joists altogether, if your sub floor is nice and flat floating floor would be solid
-- Nick H
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