Replacing ancient glazing unit fixed by glazing tape both sides, aluminium glazing bead

3 Sep 2017
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United Kingdom
Please can you give me advice on replacing blown double glazing units in aluminium frames around 35 years old? I’ve spent an hour or 2 searching but can’t find exact advice.

The removable beads are on the outside, made of aluminium and fit into aluminium frames. Glazing tape was used on both sides of the unit (to the frame and to the bead).

I took out one unit to get the sizing. Before cutting the tape the beads were impossible to move. When I cut the tape I could lever them sideways with a chisel and judicious force. Awaiting its replacement (5-7 days) I used duct tape to secure it back in. I did, though, try to refit one of the beads without tape and found it wasn’t easy. Short of time and not wanting to damage anything, I decided to research methods. I suspect the task may be harder with a sticky tape getting in the way.

The image shows a cross-section of the beading. The horizontal part is alongside the outer glass. The frame has a spline pointing inwards that engages with the V notch in the bead, which means that the bead doesn’t just slide in. The frame has a thin plastic wall around the unit with a 1mm or so gap; I couldn’t see which side the bead fits (next to the glass or not). As the frame and bead are aluminium there is no give as there might be with plastic.

Can anyone help on the way to fit the beads and the thickness of glazing tape needed (I can measure the thickness of the old tape but don’t know if it was a greater thickness that got squished)? Thanks in advance for any help.


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