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General: Closing window cavities

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  1.  
    • CommentAuthorborpin
    • CommentTimeJun 11th 2012
     
    I'm looking for a product to close the cavity when fitting a window. From out to in the walls will be render, block, 50mm Cavity, 120mm PIR, 100mm Light Steel frame. I have some accredited details (AD) and they describe "30 minute fire resisting propriety insulating cavity barrier with integral DPC".

    The idea is to put in a ply window box and mount the window inside that. The AD show the window butting against the outer (un-returned) block work.

    I would prefer to mount the window in line with the outside of the PIR, then close the cavity or actually better still wrap the insulation round a little. I had wondered about a 50x50 as the closer, mounted such that a strip of insulation could be fitted as the reveal. However I then need a bead and mesh to finish the render on.

    At the head of the window, I could extend the ply to the outer wall instead (as I was not going to render the lintels).

    Alternatively, for a quite life, I use the ADs.....:sad: in which case I need to find some closers.....:devil:
    • CommentAuthortony
    • CommentTimeJun 11th 2012
     
    I never closed them! no fancy stuff no cracks, well I did use sheet insulation on my new house with a plasterboard cover.

    there is a sketch detail on my website which has given rise to zero cracks and zero problems, no dpc apart from a tray over the lintels.
    • CommentAuthorborpin
    • CommentTimeJun 11th 2012
     
    Typical, as soon as I ask the question I find (an) answer.

    http://www.kingspaninsulation.co.uk/getattachment/65ad1abf-534f-4c2c-9ecc-e4f0c1789965/Thermabate.aspx

    Interestingly this has different solutions for Scotland and the rest of you! Why you would want to create a thermal bridge though beats me.

    Going out so will look further later.
    • CommentAuthorTimber
    • CommentTimeJun 12th 2012
     
    The 'cavity barrier' is required to meet Approved Document B and inhibit smoke and fire spread in and out of concealed spaces.

    Normally it would be a polythene sleeved mineral wool cavity barrier, something like the Rockwool TCB (others are available), or 38 mm thick solid timber wide enough to fully close the cavity.

    P.s. the thermabate cavity closers are not fire resistant, so DO NOT meet the requirements for NON masonry construction. It 'has' to be a material that gives 30 minutes fire resistance.
    • CommentAuthorborpin
    • CommentTimeJun 12th 2012 edited
     
    Posted By: TimberP.s. the thermabate cavity closers are not fire resistant, so DO NOT meet the requirements for NON masonry construction. It 'has' to be a material that gives 30 minutes fire resistance.
    The literature states it did pass the 30 minute test for integrity. Very misleading as this does not meet the Scottish regs. The Kooltherm Cavity closer on the other hand does not appear to have a BBA certificate but the literature states it has a 1 Hour resistance.

    @Timber - Can you suggest an alternative?
  6.  
    YBS Insulation and Cavity Trays Ltd offer a range of fire rated closers:

    http://www.cavitytrays.co.uk/closers/3/1

    http://www.ybsinsulation.com/products_cavity.htm

    For something more exotic you could make your own out of high density Compacfoam. It can be screw fixed to reveals &/or to form a box:

    http://www.compacfoam.com/index.php?main=2&lang=en

    David
    • CommentAuthorTimber
    • CommentTimeJun 13th 2012 edited
     
    Hmm, I will have to check out the thermabate closer. I was under the impression, last time I looked, that it was not suitable for use in non masonry builds. Interesting.

    Edited to add in the missing 'not'
    • CommentAuthorborpin
    • CommentTimeJun 13th 2012
     
    I had found the YBS one before but forgotten! Looks like it may be the best bet.

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