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Second fix

Door leaf clearance arithmetic

wleaf=W−gl−grhleaf=H−gt−gb
where
wleaf
leaf width (mm)
W
opening width (mm)
gl, g_r
left and right gaps (mm)
hleaf
leaf height (mm)
H
opening height (mm)
gt, g_b
top and bottom gaps (mm)
Explain this equation

Works out the door leaf size that leaves specified gaps all round within a measured lining opening.

W and H are the opening width and height in millimetres. gl and gr are the gaps at the hanging and closing sides. gt is the gap at the head, and gb the gap at the bottom, often bigger to clear floor coverings. wleaf and hleaf are the leaf sizes.

The leaf plus the gaps on both sides fills the opening, so you just subtract the gaps from each dimension.

An 838 × 1981 mm opening with 3 mm gaps at the sides and head and 8 mm at the bottom gives a 832 × 1970 mm leaf.

Watch out: this does not authorise trimming a door. Fire, smoke, security and acoustic doorsets have certified gap limits and trimming rules.

Deduct specified operating clearances from a measured lining opening.

mm
mm
mm
mm
mm
mm

Enter your values to see the result.

Good to know

Does not authorise trimming. Fire, smoke, security and acoustic doorsets require their certified instructions, gap limits and permitted trimming.

Limits

Flooring gaps, slide clearances, fire-door gaps, fixing schedules and finishes must follow the design and product instructions.

Sources

  • Geometry / arithmetic

This is a calculation aid, not a structural design or compliance certificate. Every default is an example, not a specification for your project.