measure in 3 places and deduct 10mm from the smalles measurement to allow for clearance.
measure to the underside of the existing sill unless it is NOT going to be replaced. IE a concrete sill is present. If u DO NEED a sill then enter the overall height measurement including the sill.
check diagonals to ensure the aperture is square, there should not be a difference of more than 5mm between the two sizes.
Aluminium Windows | Aluminium Doors
Specialising in the design, fabrication and installation of patio doors, hinged doors, pivot doors, sliding doors, sliding folding doors and stack-away doors.