The answer to your selected question is shown below.
In reality there are differences between how you measure and order a roller garage door depending on the brand, type of door and where you are going to install it - Inbetween or Behind your opening.
Most roller garage doors are installed BEHIND the structural opening and therefore you focus on the daylight dimensions for the opening and then the sideroom and headroom available.
You will need sideroom for the guides either side and headroom for the roll itself and/or the hood cover, although there is no problem with the roll or hood hanging down when you don’t have enough headroom, and the same for the guides.
If you are installing completely INBETWEEN the structural opening then your dimensions become the overall width and height for the roller door, guides and endplates, but with some tolerance taken off for installation. Usually 10mm all round off the smallest dimensions measured.
Insulated Aluminium Roller Doors
MOST roller doors of this type are ordered by the OVERALL WIDTH including the guides and then the ordering height is the GUIDE HEIGHT not including the endplates and roll dimensions.
There are some exceptions to this so please check the model carefully in our ‘measure’ tabs to see what the brand and model instruction is for ordering.
Guide width will vary slightly from one brand to another and the roll and endolate size may also vary but for most standard heights this dimension is 300mm.
Single Skin Steel Roller Doors
These are different and can only be fitted BEHIND a structural opening, whether that is brickwork or a timber frame in the opening.
The ordering width is still the guide width BUT there are fixing lugs to consider outside of these guides. The guide height, or height you want the door to stop at is the ordering height and then there is the curtain roll size to consider on to of this.