Measuring for replacement window

[headsortails]

I'm going to replace a couple of single glazed windows in my bathroom. When measuring for the new units what sort of gap should I leave.

Also when drawing windows how you denote the positioning of opener/hinges/handles?

Many thanks.

 

[noseall]

i try and make replacement windows fit as snug as possible. if the brickwork is true and plumb then 5mm fitting gap should be ok (2.5mm up each side), allow 10mm plus if the brick work is a little skewiff.

openers are denoted using a triangle drawn inside the sash, with the point of the triangle being the hinge.