Help designing and building a workshop

[threedee]

v3 redesign in view of changed material sizes (metric instead of imperial materials, some additions/changes in design).

http://sketchup.google.com/3dwarehouse/ ... ab189cfd4e

Now thinking of ways to close slope gap and make it warm.

 

[cammy9r]

hi, I built my shed in stages too. In fact I still have to choose a roof covering but it looks like that will be felt in the end as everything else borders on £700. Osb is not cheap but is cheaper than ply where I stay.
I downloaded the sketchup model and was wondering if it is exactly how you intend to build it, in regards to stud work and timber lengths and 9mm osb for the roof deck. While you could use 9mm on the roof I would say that you need to add more roof joists. For 9mm you really are looking a 400mm centres, 18mm and minimum is 600mm centres. As it stands you have 968mm centres.
I know you said the roof design is still in progress but the points I make, and that of others are worth considering. Osb has good racking strength but can easily snap like wafer laterally in the 9mm option.
Are you going to line the inside of your shed with perhaps insulation and sheathing?
Consider looking online for permavent eco breather membrane it is not dear and a 1mx50m roll is around £35 on ebay. I have used this product with great results for a while now. It will weatherproof the outside while allowing the inside to dry out and is uv stable for many months but will need covering eventually.

 

[threedee]

I'm still undecided about roof cover, looking for box profile tin to cover it in.
As for joist spacing, i used what i have so had to spread out a bit. Plus, i will be adding noggins to support osb of course. roof is still in design stage.

The shed will be insulated, walls and roof. Will see about floor.

I have already bought polyethylene sheeting to cover it all up, but its just that - black polyethylene (1000g). Will have to look into permavent thing, but ebay is most likely not an option since i'm in northern ireland and just that adds about 20 quid to the price to bigger things, most heavy things being completely unreacheable due to shipping surcharges...

Now i need to know where to put this membrane, on the outside of the osb or inbetween studs and osb... Advice ?

#Edit1# I'm getting really confused here. If i'm putting insulation in between joists what type roof does it make - warm or cold ? i'm getting some mixed instructions online... Plan is to put 100mm insulation in between 200mm joists, leaving a bit of a gap for air circulation.
My understanding of flat roof as it stands now is this (outside to inside):
1. Tin of some kind
2. OSB (9mm in my case)
3. polyethylene sheet (not breathable i think, for total waterproofing)
4. 200mm joists all above is sitting on
5. 100mm rock wool inbetween joists, leaving 100mm to..what ? Ventilation, but dont i need to protect insulation somehow ? Vent is direct air access via holes/openings in covering plates between top stud wall plate and roof decking osb(2). There will be no water access into ventilation as both back and front openings will be under roof lip sticking out. (i need to draw this out).
6. All will be covered in ply/osb to form ceiling inside.

questions:
7. Where does felt fit into this ?
8. Where to put breathable membrane ?

 

[SteveF]

Shed walls should be :

cladding outside
osb
frame with insulation inside...remember air gap if solid insulation
vapour membrane
internal cladding ....plywood or plasterboard

or if u have the time \ money \ space

u can vertical batton between the osb and cladding so that any water that passes thru cladding doesn't soak the osb and just drips out the bottom

 

[cammy9r]

insulation between joists makes it a cold roof that should require ventilation above the insulation.
A warm roof top to bottom is...
felt/rubber/tin, whatever is waterproofing choice
18mm roof deck (sometimes it is just straight to insulation)
Rigid foam insulation
Vapour Barrier
18mm or so roof deck
Firring strips
joists
ceiling
This is how the warm roof on my kitchen extension is done in Scotland

Did you check out how I built my shed in stages...
for-threedee-maybe-of-some-help-t73560.html