DIY Doctor

Window fitting and salvaging a bad job

Postby niftyprose » Sun Jun 28, 2020 1:23 pm

Hello guys, I've found a lot of useful info here but this is my first post. I hope I've clearly expressed a complex situation.

My girlfriend has asked me to look at the installation of her sitting room window, which was done before I came on the scene. It's a bit of a mess. The wooden timber frame has been fitted straight into the reveal in a brick-and-block wall. There's no DPC and the frame is too small, leaving a 2cm gap l+r and 1cm at top. The gap has been filled in with a thick layer of render and the gap between timber and render has then been filled in with some kind of silicon sealant. Under the circs it's no surprise that there's a damp problem on one side of the frame. (I'm surprised that it's not happening on both sides!)

I imagine the best way to proceed would be to remove the window frame, build up the sides of the brickwork to reduce the size of the gap, then refit the frame with a proper DPC in place. However, that's a large job, and would require a lot of cleanup inside the house.

I'm inclined to dig out all the surplus render, run a high-quality weatherseal around the window frame, push nylon slats into the gap between frame and brickwork and screw them into place, then render over the nylon. I know it's brutal, but it could be done without disturbing the window.

Let me know if you can suggest a better way...

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Simply Build It

Postby stoneyboy » Mon Jun 29, 2020 10:21 pm

Hi niftyprose
Really the window should be removed and trimmer pieces fitted to make the window the right size for the opening? You could remove render fill replace this with expanding foam and then fit a moulding to cover the gap.
Regards S
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Postby niftyprose » Mon Nov 02, 2020 4:54 pm

Hi all, especially Stoneyboy,

Thank you. I think that was good advice.

I'm posting this in case anyone else finds themselves in a similar position. First thing to say is: Stoneyboy is right! A proper refit is always your best bet.

We couldn't do if for various reasons. The following worked OK and is holding up through bad rain.

I put a heavy duty door seal up the side of the window frame. Good adhesion because it's sticking to plastic.

Then I pushed a thick plastic strip -- the kind they sell for inside plastering jobs -- into the gap between seal and reveal. I sized the strip and the seal carefully so it was a tight fit. I left just enough of the strip outside the seal to screw it into place in the brickwork.

Lastly I fitted a plastic render corner bead over the strip and rendered, which meant that the render was well-seated and overlapped the door seal. (You can barely see the rubber unless you line up just so.)

Can't promise it will last forever but it's doing OK so far.

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