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Crack and orange strain around uPVC window

  • 04-09-2022 6:05pm
    Registered Users Posts: 125 ✭✭

    Hi all,

    Just looking for some suggestions as to what this might be.

    The window at the back of the mothers house has developed some cracks, above the window there is a small crack appearing on the grey wall and also around the uPVC window itself, there is also this orange/green stain which can be cleaned but returns.

    For some context this is on the an extension with flat roof, the roof was replaced around October 2021. The extension has been there 20 odd years.

    Here are some pictures of what I'm talking about

    Any suggestions or advice would be great.


  • Registered Users Posts: 1,889 ✭✭✭whizbang

    Loke like a water stain where water is exiting, maybe entering through the crack above the window reveal.

    Open this up and fill it and seal it properly.

    Seems a lot though; any chance theres a leak somewhere else? Dampness in the wall inside maybe ?

  • Registered Users Posts: 5,569 ✭✭✭10-10-20

    That looks like a failing window lintel due to water ingress alright. What year was the extension built? I can also see the marks from what appears to be pumped insulation in the wall above the window, when was this completed? What room is this (kitchen/bathroom)? Are any other windows showing similar signs?

    The lintel is a stainless-steel or galvanised component which supports the bricks above the window over the length of the window.

    The lintel is created with a lip sloping downwards to allow any moisture which collects on it to move to the outside leaf. Newer lintel installs require weep-holes along their length to allow for some drainage, but these were not included in older houses. In your case as whizbang mentioned, you could either have moisture tracking in from the crack above the window, or more likely moisture is collecting within the wall as condensate and working downwards. The former is somewhat unlikely as there would have had to be a crack there first, so it's a chicken & egg scenario in that regards. It appears to have caused the lintel to weaken, opening that horizontal crack even further and probably allowing more moisture to enter.

    The risk here would be that the upper reveal (the white-painted concrete) could fail and/or that the bricks above will weaken. You'd be best advised to engage a professional to identify the cause of the moisture and recommend remediation. I'd hope that replacing the lintel by removing the lowest course of blocks and supporting the remaining blocks above would suffice once the moisture source has been dealt with.

    Post edited by 10-10-20 on

  • Registered Users Posts: 71 ✭✭bfclancy2

    99.9999% sure that a steel lintel was not used in this scenario, yet to see the under side of steel lintel plastered such as is shown in the OPs images. Prestressed concrete lintel most likely used. Its rendered so no need for weep holes, these are never used in this application.

  • Registered Users Posts: 5,569 ✭✭✭10-10-20

    Looking again at the close-up of the sash window, there are seemingly two 'residues' on the top frame of the window unit. First is a green algae which clings to the top portion of the frame and the second is a reddish rusty residue which appears to have traveled with the water and remains around where the sash seals with the frame. To me, the algae is a sign of prolonged damp.

    If it was a pre-stressed concrete lintel, then it likely has steel reinforcing, right? Could we be looking at spalling within the concrete from expansion of the steel due to retained moisture (from an unknown source), with the residue moving outwards with weeping moisture.

    Then looking at the rough finish to the render/paint on the wall to the right of the windows, could we be looking at a bloom due to dampness from the flat roof above?