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    • CommentAuthorgyrogear
    • CommentTimeJan 28th 2017 edited
    I have an inbuilt garage under my lounge. L = 5.6 m x W = 2.8 m x H = 2.3 m. Bare block walls.

    I have already insulated the floor with 30mm XPS and 9mm OSB.
    Currently insulating the outer (East) wall with 40mm XPS and lime render over.
    (we have EWI but it only descends 10" below the floor slab...).
    (in 1983, one did obviously not EWI a garage...).

    Inner (West) wall = uninsulated since party with ex-Car Port, which is sized idem garage but we put patio doors across it several years ago and it is now our Basement Warmer / multifunction entrance lobby / PUB and our front door is generally always open as we get warm air into the basement...

    (Intermediate Apologies for the Long Post...).

    I built an airtight insulated partition across the back of the garage with a sliding door in it, to form an "air lock".

    The (south-facing) Garage door as-yet untouched (1983 vintage, wooden folding). I want to build a solar collector in the reveal in front of the door, to grab heat (= technology demonstration)...
    The idea is to heat the garage with solar air (from 100 sq.ft aspirated slate facade...), cycle the warm air back through the glazed collector, Roast the Garage, which becomes a hypocaust of sorts.
    The garage air is then dragged into the Crawlspace, where I have several tons of water etc.

    So much for the plan... and now for the question...

    I am currently wondering about the garage Roof... the other side of which is my Lounge Floor...

    Currently garage gets awfully chilly (leaky door...) and no doubt impacts the heated volume...
    (the Car Port gets down to 14°C these chilly nights). (Even the CS manages to hold 15°C).

    Apart from heat-loss aspect, logically I need to insulate the Garage Roof for inertia reasons, and per other post, http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=4679&page=1#Item_9
    spray-on PU by a contractor is the way to go...

    The floor composition from top down is: glazed earthenware tiles (10mm); cement screed with (redundant) electric radiant infloor heating ; 9 cms of concrete with wire reinforcement; 70mm EPS insulation; 50mm of fireproof interjoist fillers ("Fibralith" woodfibre-cement). Joists are reinforced concrete on 60cm centres.

    The question (finally...) is, how to attach plasterboard to PU foam ? I doubt that mechanical fixings into the joists would be allowed. However, the fibralith provides basically no hold to a screw... So I am imagining a grid of stud track, fixed across the underside of the PB, and secured to wall brackets.
    Opinions appreciated as always...

    (More Apologies for long post...) :cry:

    If you can't fix to the concrete beams why not miss the beams and fix appropriately spaced battens into the 9cms of concrete with long screws.

    Given that your floor already has 70mm EPS and the 50mm of fireproof interjoist fillers (which I presume also add some insulation) how much more are you planning?

    Are you wedded to the sprayed PU foam, otherwise fix EPS to the ceiling with the standard EWI adhesive and would the adhesive render/glass mesh as per EWI give enough fire proofing. (you are only fire proofing the EPS as the ceiling/floor already has fireproofing) If you treated it like an EWI solution then you probably wouldn't need mechanical fixings at all
    • CommentAuthorgyrogear
    • CommentTimeJan 28th 2017 edited
    Hi, PiH, and thanks for the response !

    Posted By: Peter_in_HungaryAre you wedded to the sprayed PU foam

    No, I am not wedded to anything, except killing some unnecessary & unwelcome coolth !

    Thanks for the battens idea - however it sounds like a lot of work - I found THIS...


    and the bit about sagging and 45 cm centers put me right off !

    So I think I'll use 50mm XPS bigboards, cement them direct to the soffit then render them with a good coating of my favourite homebrew mudcrete !

    [To be honest, this job would have been done & forgotten about, 2 yrs ago, when I did the garage air lock and was all gung-ho; however at that time (and I am not likely to forget...) I made the error of asking the opinion of my brother (retired master plasterer...) who tore me to pieces... for suggesting cementing the XPS, then cementing PB to the cemented XPS and "holding the edges up" with my 40mm wall insulation...] one lives and learns :shamed:

    So thanks again for the input, looks you just got me kick-started, finally ! :devil:

    • CommentAuthorgyrogear
    • CommentTimeApr 22nd 2017 edited
    Hmm, I am back again !
    I got the XPS up OK, Now I am waiting for a new garage door (to be fitted 1st June).

    This is a sectional door with a motor drive and two roof tracks to receive the open door.

    At this stage, I am trying to pre-empt problems, such as will the contractor want to drill into my reinforced concrete joists, to fix the roof-mounted gear...

    The joist fillers provide no hold to speak of (they are wood fibre and cement) ("Fibralith by Knauf" or equivalent). (I cemented the XPS to them, and followed up with plastic fasteners and "nails") (and PVC cement to the concrete beams).

    If he does not drill the joists, then he will be penetrating the interjoist bays and drilling into the slab above - I have calculated this as being 8 or 9cms thick. However, it has infloor radiant electric in it, so I am anxious that he does not wreck my radiant floor installation !

    I am unsure whether drilling into a RC joist is OK, even; they are an inverted "tee" shape, the flange being 10 cms wide and the web narrower - it forms a "shoulder" that the interjoist fillers sit on).

    All feedback / reassurance welcome !

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