The hidden sins of retrofit double-glazing

Every day someone asks us about fitting thicker glass or double-glazed units into their old windows.

There are plenty of companies out there that will sell you the glass you want.

But many of them don’t know how your windows work, and end up breaking them in the process. Then we get called in to make the window work again!

The problem is that when people fit thick glass and double-glazed units into old wooden window sashes, it makes the sash much heavier. To keep the sash operating, you have to add just as much weight to the other end of the rope.

With all that extra weight, the ropes and the pulleys come under a lot more strain. And the box where the counterweights run up and down can become overcrowded.

Two weights on one cord jam in the weight pockets.
Weights are wired together onto a conventional cotton cord. It won’t be long before the cord breaks, leaving the window inoperable. 

We often see shoddy workmanship in these situations. Ropes that are not strong enough to last; original lightweight pulleys that are left in place; and windows that won’t work properly because the counterweights have stuck.

One common trick in the double-glazing retrofit industry is to permanently screw the top sash shut, and to steal the counterweights from the top sash. Trouble is, the top sash will never work again, and the bottom sash is also likely to jam from carrying a bulky and unbalanced counterweight.

At Sealasash we understand how sash windows are meant to work and when we fit heavier glass we re-weight each sash properly with lead counterweights. So all the sashes work effortlessly.

Its important when you are considering re-glazing your windows with new glass that you ask the service provider if they guarantee they will make your sashes balanced and all work properly. Fixing shut sashes that are meant to move, particularly bottom sashes, will cause long-term rot issues.

If you would like to talk to a timber window expert who understands all your options, and who will listen to your priorities, then please don’t hesitate to contact us.

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