Damproofing

Discussion in 'Engineers' Talk' started by wardoss, Feb 4, 2004.

  1. wardoss

    wardoss New Member

    Help

    With the recent wet weather I notice yesterday that I have a damp patch at the head of my stairs window.

    This window is a recently replaced UPVC and I don't think its a bad seal around the window.

    The house is 60s ex council and when I look at the wall the brickwork has a shine when wet, I think that the bricks have become very porous and the water is seeping through the bricks

    What are other peoples thoughts
     
  2. Gotcher

    Gotcher New Member

    If there was no damp before the window was replaced then I would have thought you need to get the window company back in to effect repairs.

    Gotcher
     
  3. The Trician

    The Trician New Member

    Could be condensation? Cold air up your cavity!
    Cold surface indoors+warm moist air=condensation?
     
  4. everhopeful

    everhopeful New Member

    1960's - it probably was fitted without a lintel i.e. bricks laid upon the window frame. This was quite common then. PCV replacements in these cases sometimes need a lintel as PVC is not normally load-bearing. It may be that the brick lintel (so-called) has sunk leaving a small gap that lets water in. Look at the outside using binoculars if necessary to see if there is any gap. If there is, get them back.

    There again - if there wasn't a leak before why not get them back anyway?
     
  5. Tangoman

    Tangoman Well-Known Member

    I have a similar problem -
    Lots of the plaster was blown on the wall, removing it the wall feels damp underneath and the beading has corroded.

    Checking the outside - no sign of a lintel. There is a piece of wood running across the top of the window (which is UPVC) which has been repointed above, but there is a 2 mm gap between the pointing and the brickwork above, suggesting that the window has dropped slightly since fitting.

    Not a recent fit though - was in when I bought the house 3 years ago.

    Thinking of chipping out the pointing around the window and replacing. Would this cure it? No damp near the bottom of the wall.

    Cheers,

    Tango
     
  6. unphased

    unphased Screwfix Select

    Just because you cant see the lintel there could still be one. If a steel angle was fitted the brickwork would sit proud and hide it. The window was probably made undersized and the timber put in to make up the gap. If the window head hasn't been properly installed water will find its way in and hence cause the damage you have seen.

    I would take the timber out that you have seen as this will be rotten by now (or getting that way). Fit a treated timber bearer to a good close fit above the window and for length then seal around it with plenty of mastic. Then face this with another timber to just overlap the window edge and give this a good coating of paint(prime u/c and gloss) then point around the repair as necessary. Should do the trick.

    RSS
     
  7. Tangoman

    Tangoman Well-Known Member

    There is a lintel - I can see it on the inside wall which I've stripped back.
    I am sure you are right about the timber - definitely a case of window too small for original hole.

    Condition of timber looks ok - no sign of deterioration at ends where you might expect it to rot.

    What's a timber bearer? I'm guessing it's just a piece of timber and the bearer part is because of where it goes? or is it a special type of timber?

    It's strange that the pointing underneath the window is also slightly cracked! Looks like window has shrunk with time!

    Cheers unphased!
     
  8. unphased

    unphased Screwfix Select

    Sorry Tangoman a bearer is just a term I used, nothing special. :) Glad you have found the problem though.

    The "shrinkage" you are seing around the window frame is almost certaintly due to excess cement in the mortar used to point around the frame of the window and the mortar has shrunk and cracked leaving the frame to move. PVC wont shrink. I would double check the timber "packer" (perhaps bearer wrong term) at the window head to see whether it i still okay to leave in before you seal all the frame up again.

    RSS
     
  9. Tangoman

    Tangoman Well-Known Member

    Thanks unphased-
    I know the window itself doesn't shrink! (Just thought I'd point that out!) Just commenting that it looked like it had shrunk. The mortar explanation is good. Didn't realise though that it would affect it this much. What's the best way to get around that when repointing? Use a very wet mix? or put it on in layers?
     
  10. unphased

    unphased Screwfix Select

    Hi

    To avoid excessive shrinkage in the mortar use builders sand (not sharp sand) and only mix 5 parts sand to 1 part cement by volume. This will give a more than adequate mortar strength. As for the consistency dont use it too wet. It should just stand up and keep its shape on the trowel and be easy to work. Err on the dry side if unsure.

    RSS
     
  11. Tangoman

    Tangoman Well-Known Member

    Thanks unphased - I'll give that a go.

    Another job for the long list :(
     

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