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Externally Insulating existing garage

  • 11-01-2009 1:04pm
    #1
    Builderfromhell
    Registered Users, Registered Users 2 Posts: 1,570 ✭✭✭


    I would appreciate comments and advice on the following proposal.
    I am building a room over an existing garage. Garage is Hollow block wall. had originally intended to dry line internally but afetr what I've read here I will avoid dry lining from now on.

    GROUND FLOOR
    Insulation boards fixed to plastered hollow block wall externally. Have not yet decided on type of insulation. Looking at aerobord 100mm.
    Mesh fixed to insulation.
    Special render over mesh.

    FIRST FLOOR
    From outside in as above except that insulation is fixed to 11mm OSB board
    on 100 x 44mm timber studs.
    100mm rockwool between studs
    11mm OSB board with joints taped so as to achieve vapour control layer
    25mm battens to give service void
    12.5mm plasterboard skimmed and painted with emulsion.

    My concern is that if I use aerobord or Kingspan as external insulation I may inhibit any moisture at 1st floor from getting out (should Vapour membrane fail).


Comments

  • #2
    RKQ
    Registered Users, Registered Users 2 Posts: 2,292 ✭✭✭RKQ


    Not 100% sure I follow. ( Can't see how exterior surfaces line up!!)
    Any chance of a quick sketch section?

    How do you plan to line up exterior ground floor with timber framed first floor?

    Will you cast a conc ring beam for stability?

    If its a domestic garage I'd be inclined to dryline.


  • #3
    Slig
    Registered Users, Registered Users 2 Posts: 1,550 ✭✭✭Slig


    Aeroboard doesnt breathe and kingspan (or any PIR insulation)should never be used if there is any chance of moisture as it desintegrates


  • #4
    Builderfromhell
    Registered Users, Registered Users 2 Posts: 1,570 ✭✭✭Builderfromhell


    Changes to specification as follows;

    GROUND FLOOR
    KIngspan Insulation boards fixed to plastered hollow block wall externally.
    http://www.rockwool.co.uk/graphics/RW-GB-implementation/brochures/RockShield_Application_Guide.pdf
    Mesh fixed to insulation.
    Special render over mesh.

    FIRST FLOOR
    From outside in as above except that insulation is fixed to 36mm Softwood board
    on 100 x 44mm timber studs.
    100mm rockwool between studs
    11mm OSB board with joints taped so as to achieve vapour control layer
    25mm battens to give service void
    12.5mm plasterboard skimmed and painted with emulsion.

    I tried to upload details but file is too big.

    What I am trying to achieve is a reasonably warm wall that effectively breaths. That is why I have changed outer board to softboard. This, I believe, will allow any trapped moisture to escape and provide additional insulation. I cannot get 36mm softboard so I am using 3 layers of 12mm softboard.

    Detail is similar to this; http://www.greenspan.ie/PDFs/Outsulation/Outsulation%20Details.pdf
    except thast I am proposing breathable Rockwool.


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