Replacement windows sizing advice

[cheradenine]

So my mission to replace old single glazed steel windows continues.

Our single glazed windows, unless I'm much mistaken, are like [1]. They are odd-leg frames, in imperial sizes, where the long-leg extends 1/2" more than the short.

I am intending to replace them with [2], in I assume in a long-leg variant.

The existing windows I suspect are original and were fitted as the house was built. There is no timber subframe, outside they are direct to brick (with a tile sill at the bottom), and on the inside the wall provides the fit (the windowsill where present disappears under the frame) - the windows are screwed through the side of the frames into the wall.

Being historical artefacts, I know the exact (imperial) sizes that they were manufactured in. For the most part, the outside is pretty snug to the brickwork.

So the question is - how much smaller than the original dimensions should I order replacements? I've heard 5mm (giving 2.5mm all round) as a guide. Does that seem reasonable ?

IMG_1574

• cheradenine
• 31 Mar 2016

IMG_1566

• cheradenine
• 31 Mar 2016

windows

• cheradenine
• 22 Mar 2016

windows

[1] http://www.periodmetalwindows.co.uk/images/p029_1_01.jpg
[2] http://www.duration.co.uk/technical...utty-line Windows Sections Identification.pdf

 

[Gazman16]

Oh those will be fun to get out! You will probably have to cut them to bits with an angle grinder.
Assuming the brickwork is straight, Square and plum I would go 10mm smaller on height and width than the smallest measurement. That would give you a 5mm gap all around for some expanding foam and expansion.

You will have to check the aperture sizes, levels and squareness quite accurately though