Brick coalshed insulation

Discussion in 'Builders' Talk' started by rcoup, Nov 13, 2017.

  1. rcoup

    rcoup New Member

    Hi all, I've been doing a lot of reading of the forums, and I think I've come up with a plan, but would appreciate a once-over from someone who knows this stuff.

    We've been in our mid-50s brick house about 2 years, and we have a detached coal shed (~2.2 x 2.4 x 2.4h internally) which currently houses the dryer (externally vented). I want to tidy it up and use for additional storage and drying wet outdoor & sports gear. We have some old kitchen cabinets which would do nicely for fitout. My idea was to add some basic insulation then use an electric towel rail for drying wet things out as we need to.

    It's a single brick width ("single skin"? "half brick"?) all the way round, with an additional brick width externally at/below ground level (which is between 1 & 2m high on three sides). No cavity that I can tell (the external brick has a concrete cap). No external rendering. No windows. The floor is a concrete slab. The internal walls are painted. The shed gets damp during winter, particularly in the back corners, but not really wet. I can't see any DPC. See the photos :)

    Roof is 4x2 joists with OSB + felt. There's not enough fall on the roof (<20mm over 2.8m) and the felt is giving up, during winter the OSB is wet (& water pools -> more wet). So that needs replacing.

    So from my reading:
    * liquid tanking sounds ideal, but seems like it requires me to strip all the paint from the floor and the walls first, which sounds like an A-grade pain. So currently thinking black-plastic DPM from on the floor and all the way to the top of the walls. Attach via glue, and make sure the floor plastic is on top of the wall plastic at the edges up 150mm or so.
    * Then adding foil-backed Celotex/something 25mm insulation on the floor, with cheap laminate/vinyl/something over the top.
    * 25+12mm Kingspan/something insulation with integrated plasterboard on the walls. Tape the seams, skim and paint.
    * For the roof it seems like (since I have to replace it anyway), I might as well do a warm roof. Lift the joists to fix the fall, then 18mm OSB -> adhesive vapour barrier -> 50mm tissue-backed Celotex/something -> EPDM.
    * Then a plasterboard/plywood ceiling if I'm feeling enthusiastic

    Does that sound sane? Completely overkill? Missing something critical? Anything obvious I can do to save money/time/effort and get the same result?

    Some other questions I'm still unsure on:
    1. Does the mesh-style bubble-wrap DPM provide any benefits over straight plastic on the walls?
    2. consensus seems like drilling through the DPM into the masonry for fixings isn't a bit deal, throw some silicone in the holes if I'm keen?
    3. my gut feel is that wall cabinets fixed through the insulation into the masonry would be ok strength-wise, given long enough fixings & plenty of them? If not, could I add a couple of strategically placed wall battens and use the vapour barrier tape between them & the wall insulation panels? Otherwise I guess I'll need to go for framed walls with insulation in between, and foil-backed plasterboard over the top?
    4. There's a grill on the back wall I could replace & connect through, would that be enough ventilation? (the dryer is already vented externally)

    Thanks all, Rob :)

    Attached Files:

  2. Bob Rathbone

    Bob Rathbone Well-Known Member

    Hi Rob, using this as a drying room will introduce high levels of moisture, their are some basic rules, they are
    1/ never put the vapour barrier on the cold side of the insulation, all of the other basic rules are the same.
    I would build a wooden frame to support the plasterboard 50 x 75 will do, fit a DPC where it stands on the floor and space it away from the bricks, fixing with galv brackets. Cut solid foam insulation to fit in the frame and fix with expanding foam dabs. Cover all of this, and the ceiling insulation, with a vapour barrier stapled to the wooden frame. Fix plasterboard and finish. How you do the floor is up to you but if it is flat and level, I would lay styrene insulation about 10mm thick with a silver foil vapour barrier on top and use some cheap laminate flooring. If you can't ventilate properly, get a de humidifier and leave it on in the room, it will stop the plasterboard getting wet with the water you will be introducing into the air.
  3. rcoup

    rcoup New Member

    Hey Bob,

    Thanks for your input. How big an air gap are you thinking around the walls? 20mm enough? The doorway is hard up against one corner, so I don't have a huge amount of room to play with along the wall next to it.

    Cheers :)
  4. KIAB

    KIAB Well-Known Member

    Last edited: Nov 14, 2017
  5. rcoup

    rcoup New Member

    @KIAB so that then the DPM? Or just attach the insulated boards to the walls?
  6. KIAB

    KIAB Well-Known Member

    Could go smaller than 3x2 stud work,here I used 2x1 & 25mm of Celotex insulation,as space was at a premium on one wall, & vapourcheck plasterboard which will give you your vapour barrier.

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