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Office Shed build: shed is up but what next?

Discussion in 'General Trade Discussions' started by rich1983, Aug 12, 2017.

  1. rich1983

    rich1983 Member

    I had a shed built a couple of years ago (12x12) and I put a bugger load of celotex type insulation in and then boarded over it. Depth of cavity between timbers is 70mm for walls and 150mm for ceiling.

    I had huge problems with damp and condensation and was told that I should have done the following (in order from the actual wooden wall)...

    - 10mm batton strips to make an air gap behind the insulation.
    - breathable membrane (over batton?)
    - 60mm celotex (or similar)
    - plasterboard

    - similar for ceiling but circa 140mm insulation? Would I need to membrane the ceiling considering the roof (sealed felt) isn't breathable anyhow?

    Does this sound correct? I was told that my damp problems were probably due to the fact that the shed walls would become damp and perhaps let a little moisture in which wasn't then escaping as there was no cavity. I have been told that the batton coupled with the membrane will allow any moisture that gets in the shed to evaporate outwards, as opposed to going to the highest point in he shed roof (being the front wall and ceiling as it's just a pitched roof running down to the back gutters).

    I don't want to bugger this up again and have to shell out for all the kit again. To be honest tho only some of the plasterboard was buggered (but I checked it all) and the insulation I had was given to me from Freecycle. It was 100mm depth and I had to cut it down the middle (one of the shittiest jobs I have had to do) but will just buy some proper stuff this time to make sure it's all good.

    Can anyone give me any further tips or advice? I'm literally back to the woodeb boards now.[​IMG][​IMG]

    Sent from my Nexus 6 using Tapatalk
  2. theshed

    theshed Member

    You should have put polythene layer between the celotex and board.
  3. rich1983

    rich1983 Member

    Polythene between the plasterboard and celotex or the shed walls and celotex?

    Sent from my Nexus 6 using Tapatalk
  4. Stevieo

    Stevieo Active Member

    What insulation are you using?
  5. choppa

    choppa Active Member

    Porn fridge beer done.
  6. theshed

    theshed Member

    plasterboard and celotex
  7. rich1983

    rich1983 Member

    Celotex board type stuff I figured maybe polystyrene but celotex appears to be about 20% more effective.

    Do you have any suggestions?

    Sent from my Nexus 6 using Tapatalk
  8. rich1983

    rich1983 Member

    I've got the computer in there already. My beers don't require refrigeration so it looks like I'm done :)

    Sent from my Nexus 6 using Tapatalk
    • Like Like x 1
  9. theshed

    theshed Member

    20170812_195416.jpg 20170812_195333.jpg 20170812_195320.jpg This is one I did for my mate.
    • Like Like x 1
  10. rich1983

    rich1983 Member

    That's what I'm aiming for with regards to internal finish. Did the list I put up (the order of things etc) miss anything other than polyurethane?

    Sent from my Nexus 6 using Tapatalk
  11. theshed

    theshed Member

    It had 50mm celotex flush with the timber on ceiling with 6inch square gaps for down lights. 50mm celotex flush with timber inside then polythene walls with 8in overhang stapled to the ceiling. Run cable for sockets on top of wall joist then cut plasterboad strips to pack out to cover cable and then board on top. I chose to tape and joint with paper tape because i was worried about skim cracking. Those photos were taken tonight, it's 18 month's old now.
    • Like Like x 1
  12. rich1983

    rich1983 Member

    Sorry Mr theshed, but I don't quite follow...

    Should I use the membrane as I described? Plus the polythene you suggested?

    I was going to put the electrical cable horizontally through the frame, drilling through the uprights to cater for it. Same for the ceiling, was just going to drill through the beams for the ceiling light cable.

    Also you didn't skim: just tape and fill and then painted?

    Finally did you do anything for ventilation
    ? I see there are loads of double glazed windows in that she'd. Did they have vents in? I was thinking about putting a small square vent in front and back to create a draft to keep moisture down, especially if I end up sealing it up (fill and tape or skim).

    Sent from my Nexus 6 using Tapatalk
  13. theshed

    theshed Member

    Just put the membrane under the plasterboad on the walls. By running the cable on top of the wall joust, polythene over the top and then plasteroard the joist gives you enough room to fit plastic drywall boxes for sockets. My mate used second hand double glazed windows £30 each and second hand door off of ebay. I would never polythene the ceiling.
  14. malc

    malc Private Member

    why polythene? why not use Tyvac a breathable membrane.
  15. zombie

    zombie Private Member

    defo not polythene that would cause mould spores!!!

    As @malc says you want roofing felt breathable membrane
  16. gps

    gps Private Member

    Also agree, shouldn't it of gone on the outside though between the timber and cladding
  17. Dropsalot

    Dropsalot Private Member

    Did mine years ago with breather paper......worked fine until the roof felt failed.
  18. flynnyman

    flynnyman Private Member

    You don't need the battons just celotex across and board straight on top. You could vent each bit with a couple of holes if you wanted. Forget the polythene the celotex does that job, aslong as there are no leaks it should be fine, maybe get a hose on it just to check? What you doing with the floor?
  19. Stevieo

    Stevieo Active Member

    I'd go with the polystyrene slabs.

    The wood breathes so you won't get any condensation and unless you have heating, you aren't really insulating anything because there's no heat to keep in. You're just keeping the wind out.

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