Window/ Install

26 Dec 2017
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United Kingdom

I am looking to potentially install some windows, I want to understand how windows are installed just for my general understanding as much as anything.

I have attached two technical drawings that I found on the Internet, could someone tell me if both are okay in the way they are installed.

I ask because drawing 1 seems to be somewhat different to drawing 2. Drawing 1 has a subsill under the sill, is this actually required? Drawing 2 seems a lot simpler, would installing windows like drawing 2 be adequate?

Do window installers, builders actually usually required technical drawings like the ones below to be able to install a window or not?

Many thanks


  • Windows Drawing.pdf
    120 KB · Views: 93
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Two sills is a bit random, as long as one overhangs properly it will be enough.
To minimise thermal bridging you need to line up the window with the cavity, but on old houses it's usually installed into the outer leaf as you see.

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