Building regs advice – window size

I’ve attempted to read and understand the building regulations on window sizes, I know there is a minimum opening size of 450mm x 450mm to serve as an emergency escape but is there also a minimum aperture size for a room?

I’m looking to convert a large upstairs bedroom (12 x 17 feet) into two rooms; the newly created room will be a small sized single bedroom (about 60 sq ft) . The room already contains two windows, one is large (1140x1140mm) and the other window is smaller (580 x 1000mm).

The smaller window meets the building regs for serving as an emergency escape but I’m seeking confirmation that a window size of 580 x 1000mm ( the is the size of the aperture the glass is smaller) is satisfactory for a single bedroom.

Groupon etc?

Ring your local BC officer.

You require 1/20th (5%) of the floor area as opening space since a bedroom is classed as a habitable room. You may also require background/trickle ventilation (usually in window frame). You seem to have means of escape covered.

I think the 5% rule applies to windows that open wider than 30 degrees. If the window has a stay that restricts it opening any more than 30 degrees, then the opening pane has to be 10% of floor area. See Building Regs Part F