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Single skin block building - best way to proceed?

Discussion in 'Building' started by apples12, 5 Dec 2021.

  1. apples12

    apples12

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    Hi all

    We've recently moved into a new house where the previous owner built a fairly large (4m X 6m) concrete block shed/building but left it largely unfinished. When we viewed the house the walls were already up and the frame for the roof, he simply finished it with a felt roof and left it at that.

    Since we've moved in, I've added a door and window to make it watertight..or so i thought.

    We have driving rain along with water trickling down the walls from the flat roof which is seeping into the blocks.

    The construction is: concrete base, 2 brick course of engineering bricks, damp proof membrane, single skin concrete block walls, timber roof frame and felt flat roof.

    My intended use for the space is storage and home gym.

    I have managed to get power in there (armoured cable back to fuse Board and a sep mk mini consumer unit in the outbuilding)

    The blocks of course aren't waterproof and are only a single skin, I have purchased sika waterproof coating to coat the exterior with before a membrane is fitted and the walls clad.

    The roof is also being replaced with an EPDM roof and the pitch raising as appropriate (a good friend is a roofer who fits these and he has agreed to help sort this)

    My question to the forum is, what is the best course of action to insulate the inside? Ideally it would have been a double wall construction with a cavity but I don't think I can add an internal course of blocks around as they'd no doubt be resting on the inside of the concrete slab as opposed to on the foundation?

    Do I batten and fill with celotex-type foam, or fibre insulation?

    If using the above method, do I need to add any membranes between the wall and studs and again between the studs and plasterboard?

    Or is there a 3rd option?

    Many thanks



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  3. mrrusty

    mrrusty

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    If you are redoing the roof, I would insulate and clad outside. 50mm battens infilled with 50mm PIR. VCL cross battens to form cavity, cladding eg cement board planks
     
  4. apples12

    apples12

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    Thank you

    This was my preferred route as it meant I could maximise inside space, only issue is along the wall with the neighbors, I've only got 1.5 foot of space in which to work!

    Am I right in thinking it would be as follows for the outside

    1. Concrete block wall
    2. Batten with celotex-type foam infill
    3. Vapour control layer
    4. Concrete board/cladding

    Would I need any membrane between the wall and the battens/insulation?

    Disregarding cost, what would be the best way to do it?

    Also, it insulating on the inside instead, would it be the same 'sandwich'?

    1. Concrete block
    2. Insulation (foam or can I get away with fibreglass/rockwool type stuff here?)
    3. Vapour control barrier
    4. Plasterboard/skim

    Doing it on the inside would of course mean I'd still need to waterproof the outside with some sort of render/coating but this would be easier in that problem wall where there's very little space to work (at its narrowest it's 2 drainpipes wide!)
     
  5. Notch7

    Notch7

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    this is the best advice.

    Altering the construction so it has a cavity, is the only sure way of stopping damp getting through.
     
  6. ^woody^

    ^woody^

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    Read some of the hundreds of garage conversion threads.

    Line the inside with a membrane if you are rendering, or the outside if you are cladding.

    Part of your problem there is that the roof edge is wrong on several sides and allows water to run down the walls.

    It's all in the detail.
     
  7. apples12

    apples12

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    Yup, we've identified the roof is a major issue, roofer friend is coming to amend this, we'll be raising it at the long side over the door by about 5-7cm and overboarding to fit an epdm roof over the top with appropriate edging, fascia boards and soffits
     
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