Cavity wall capping...

Discussion in 'Builders' Talk' started by TaDa, Dec 9, 2013.

  1. TaDa

    TaDa New Member

    From inside the loft I can easily see into all the cavities in my cavity walls.

    Should I try capping them in some way?

    If so, how?

    Thanks
  2. Sean_ork

    Sean_ork Screwfix Select

  3. TaDa

    TaDa New Member

    Can you expand on that?
    (There are things on the market to fill and/or cover these holes)
  4. Sean_ork

    Sean_ork Screwfix Select

    how old is the house and where are the air bricks/vent ?
  5. TaDa

    TaDa New Member

    Built in 2000 (to pre 2000 build regs), vent on one side of the fire place in lounge, air brick at front and side
    This place is cold - one room (with a sloping roof) had zero insulation behind dwarf walls to eaves. The same void had no insulation over the ceiling of the room below.
  6. Sean_ork

    Sean_ork Screwfix Select

    I spotted your question about draughts under the cill, which made me wonder if you had one of those hastily built Barratt Homes sheds - in this situation I'd be looking to get some cavity insulation blown in, and using on open topped cavity is the ideal entry place for it.

    You should be able to get a grant for it, but be quick before ours greenest ever government stops helping people save on their fuel bills.
  7. TaDa

    TaDa New Member

    There is already cavity insulation in there - though I do not know the quality. My fear is that there are gaps in the filling and cold air is still circulating

    There is one "partially exterior" cavity wall which is unfilled - the cavity wall people refused to fill it because the only entry point was on a roof (the roof to the eaves in my eaves questions) - Any suggestions as to DIY fill this one appreciated

    Either cold air is tumbling down or hot air is being allowed to rise in the empty cavity and possibly the filled ones.

    I thought capping them would reduce this flow
  8. Sean_ork

    Sean_ork Screwfix Select

    you have to be cautious, blocking the air flow may well stop any moisture that gets between the cavity from drying, you can DIY your own cavity caps by covering suitably sized lengths of rockwool/FG insulation in black poly (bin liners) and push them down from the top a few inches - no BRE approval for the ''product'' but the results are the same (and far cheaper)

    can you see any weep vents ?

    [​IMG]
  9. TaDa

    TaDa New Member

    I can't see anything like that anywehere - should I be worrying now?

    The insulation and bag sound like DIY 'socks' - do you advocate them over capping?
    Local builder's merchants wanted about £3 for each 1.2m length sock (to fill a 100mm gap) - you way would be a lot cheaper!
    Not too sure about the itchy rockwool effect though :)
    I guess I need to get a non-bio-degradeable plastic?
  10. Sean_ork

    Sean_ork Screwfix Select

    should you be worrying ? - that depends on how long you intend to stay in the house, there's many 1000s of really badly built houses that were thrown up a while back that will start to rot from within and will require significant maintenance within the next decades

    cheap FG isnt overly itchy these days, bin liners will last a good while, it's UV that aids their biodegradability - if that £3 was for a filled length then that's a reasonable price
  11. TaDa

    TaDa New Member

    Yes, it was a filled 4 foot sock - seems quite expensive at £15 for 6m - but it would be more convenient

    Should I put a board over the top or is that just gratuitous - (they had some fire proof board at around £8 for 6m)
  12. Sean_ork

    Sean_ork Screwfix Select

    you could fireboard over, fire resistant PB might be cheaper, cut to suit

    there's only so much that can be done to bring the house up to current building regs ?
  13. TaDa

    TaDa New Member

    Thanks for all your help Sean_ork

    I just want it to be warm - or at least, stay warmer longer when the heating is off.

    I suspect that the fireboards are not going to add a great deal if I install the socks - and they sound like a right pain to fix "draughtproofly" to the top of the walls

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