1. Visiting from the US? Why not try DIYnot.US instead? Click here to continue to DIYnot.US.
    Dismiss Notice

New external door and exposed cavity- to fill or not to fill

Discussion in 'Building' started by smarriott, 29 Aug 2009.

  1. smarriott

    smarriott

    Joined:
    12 Dec 2004
    Messages:
    18
    Thanks Received:
    0
    Country:
    United Kingdom
    Morning

    I have had a set of french doors put in where previously existed a window.

    The house is about 17 years old and has a good size cavity. Trouble is the cavity appears on the inside of the house and I am not sure what to do with it.

    I am having the floor tiled in a couple of weeks and the cavity needs filling with something. The tiler suggested filling with 75mm polystyrene and he would tile on top, which sound like trouble to me.

    I was going to line the cavity with thick blue builders polythene and fill with concrete.

    Can anyone offer any advice on the best approach, obviously I don't want to be breaching the damp proofing in anyway.

    Thanks


    After removing the windows and brickwork beneath
     
  2. Sponsored Links
  3. churchilldog

    churchilldog

    Joined:
    17 Nov 2007
    Messages:
    87
    Thanks Received:
    0
    Location:
    Southampton
    Country:
    United Kingdom
    Expanding foam to "fill" cut down then tile over. Depending on size of cavity depends on what expansion foam you need.
     
  4. smarriott

    smarriott

    Joined:
    12 Dec 2004
    Messages:
    18
    Thanks Received:
    0
    Country:
    United Kingdom
    Thanks for the suggestion, I am just a little concerned the expanding foam filler will not provide the stability to tile over.

    The cavity is 4". My preferred option would be to fill with blue membrane and concrete.

    Can anyone advise if this might cause damp problems?

    Thanks
     
  5. Deluks

    Deluks

    Joined:
    23 Feb 2005
    Messages:
    6,867
    Thanks Received:
    341
    Location:
    Surrey
    Country:
    United Kingdom
    If the tiles are thick enough, then going over insulation board shouldn't be a problem if the tile actually bridges over it.
     
  6. smarriott

    smarriott

    Joined:
    12 Dec 2004
    Messages:
    18
    Thanks Received:
    0
    Country:
    United Kingdom
    The tiles are 10mm porcelain so fairly weightly, trouble is there is nothing exposed of the outer blue brick to rest them upon.

    So 4" of tile would be resting on expanding foam filler in a farly high traffic doorway. I forsee movement and cracking issues.
     
  7. Deluks

    Deluks

    Joined:
    23 Feb 2005
    Messages:
    6,867
    Thanks Received:
    341
    Location:
    Surrey
    Country:
    United Kingdom
    Tricky one, but insulation foam board should be fairly stable against thermal or moisture related movement, unlike say timber or metal.

    The problem with mass filling with concrete is that of a thermal bridge, granted it's right next to glass which in itself is 'lossy' but these things are best avoided if possible.

    What about, say, 50mm of insulation board (room side) wedged in with an off cut of 50mm thick paving slab, mortared or glued into place (decent cartridge adhesive, not copydex!)


    A pic would clear things up a little.
     
  8. Sponsored Links
  9. freddiemercurystwin

    freddiemercurystwin

    Joined:
    21 Jan 2007
    Messages:
    19,859
    Thanks Received:
    2,218
    Location:
    Devon
    Country:
    United Kingdom
    If there are any spacers fitted below the cill (ie a gap), is there any way to slide one of these

    [​IMG]

    under the cill to sit on top of the brickwork? Really, this should have been fitted before the door was inserted. Various sizes are available.
     
  10. smarriott

    smarriott

    Joined:
    12 Dec 2004
    Messages:
    18
    Thanks Received:
    0
    Country:
    United Kingdom
    I am not so much bothered about thermal loss, it's more the risk of water and damp if I fill with polythene and concrete
     
  11. Deluks

    Deluks

    Joined:
    23 Feb 2005
    Messages:
    6,867
    Thanks Received:
    341
    Location:
    Surrey
    Country:
    United Kingdom
    Then your plan should work. With regards to bridging the dpc the devil is in the detail so it's tricky to advise on here without looking at it.
    You could mix polystyrene beads into the concrete to reduce thermal loss, or cut some celcon blocks to go in the gap.
     
  12. noseall

    noseall

    Joined:
    2 Feb 2006
    Messages:
    43,379
    Thanks Received:
    2,678
    Location:
    Staffordshire
    Country:
    United Kingdom
    Fill the floor trough with screed and line it with polythene. Don't worry about thermals as the french door is one great big cold spot.
     
  13. freddiemercurystwin

    freddiemercurystwin

    Joined:
    21 Jan 2007
    Messages:
    19,859
    Thanks Received:
    2,218
    Location:
    Devon
    Country:
    United Kingdom
    I realised that, I assumed you wanted a little extra support for the tiles which the closer I suggested would offer if you can get support beneath the frame.
     
  14. DIYnot Local

    DIYnot Local

    Joined:
    3 Sep 2019
    Country:
    United Kingdom

    If you need to find a tradesperson to get your job done, please try our local search below, or if you are doing it yourself you can find suppliers local to you.

    Select the supplier or trade you require, enter your location to begin your search.


    Are you a trade or supplier? You can create your listing free at DIYnot Local

     
Loading...

Share This Page