STEP 1
Measure door opening width and height in feet and inches. This determines the size of door needed. The rough opening should be the same size as the door.

STEP 2
Measure the sideroom.

STEP 3
Measure the headroom – distance between the underside of the door lintel and the lowest point of the ceiling.

If fitting to an existing timber frame, you will need to measure the internal sizes of the frame.

STEP 4
Measure the internal Timber to Timber width

STEP 5
Measure the floor to the underside crossbar