1. Measuring at a single point only
The opening width must be measured at a minimum of three points (top, middle, bottom). Walls are rarely perfectly parallel; the narrowest reading is taken as the reference.
2. Skipping the lintel and side clearances
As critical as the door itself are the lintel headroom above it and the free clearance on both sides. On spiral and sectional systems these clearances determine the type of system.
3. Not allowing for floor flatness
A slope or a drainage channel in the floor can stop the door closing fully. During measurement the floor level should be checked at several points.
4. Leaving the electrical infrastructure until later
On powered systems the cross-section, position and earthing of the supply line must be settled before installation. A line pulled afterwards means both cost and delay.
5. Not stating the intensity of use
Two openings of the same size require different product classes for 20 and for 200 passes a day. Sharing the intensity of use during the survey is the shortest route to the right product.
