Framing a window indoor for secondary glazing

30 Jul 2012
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United Kingdom

I haven't found any information about this anywhere else so I'm posting here. If anyone has any glazing/secondary glazing/carpentry advice it'd be most welcome.

The project stems from my wonderful victorian bay windows at the front of my house, that looks over a busy road. I don't want to get rid of them, but I've researched secondary glazing panes extensively and you need around 10cm - 15cm of air space between the original panes and the new secondary pane to get maximum decibel reduction. The windows have almost no interior sills on which to install the new secondary glazing units, however - the maximum space between the old panes and the new ones I'd be able to get would be about 2-3inches or 5-7cm. EDIT sorry have checked and this is the width of the existing sills, meaning I'd have even less space than that.

My plan is to build out a frame inside around these windows giving the necessary space for the installation of the secondary glazing panes.

Before I do this however I thought I'd seek advice about:

a) Which kind of wood to use and the best way to attach the frames around the windows (brackets? wall plugs?)
b) Whether the frames would support the weight of the units
c) how best to soundproof the frame (I was thinking sealing it with some sort of acoustic gel and buffering the edges of the secondary glazing units with foam before they go into the new frames.

My pictures give a rough idea of what I'd be doing.

Original bay window specs

surrounded by frames

3d version of one of the wing windows (apologies for poor paint skills)

Finished frame with glazing
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How did this project go??? I am trying the same in an old farm house in Sweden, I am hoping to have the original windows on the outside and double glazing on similar frames on the inside, the house has old style Swedish double glazing which consists of adding an extra set of windows temporary for winter
Hi Ritid,

It did not "go" in the end - still in the process of getting the secondary glazing units, the first order came back and they were too small! I've also decided to put this in the hands of a tradesman, as I'm not confident enough to do it on my own.

The basics are feasible - I think with buttressing the new window frames could hold the secondary glazing units but heavy duty brackets are in order as wall plugs cannot hold all the weight!

Good luck with your own project!

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