overlap
OH-ver-lap
/ˌoʊ.vərˈlæp/
To extend over and partially cover an adjacent edge or surface layer.
In roofing and siding installation, overlapping courses harness gravity to direct rain down lower panels without capillary water creep into seams.
The story behind the word. Combines Old English 'ofer' (over) and 'læppa' (a fold or lap of cloth). Tailors originally used overlapping to describe folding one cloth coat flap over another to keep wind out. Builders adopted the term for layering roof tiles.
Word relationships
- lap: Lap is often used as a specific trade term (e.g. 'lap joint'), whereas overlap is universally understood across technical and general domains.
- gap: A gap leaves open space between surfaces, whereas an overlap places one edge directly over another.
Commonly confused with
- butt joint: A butt joint places two board ends together flush, while an overlap positions one edge over top of another layer.
Word family
- overlapping (adjective): Extending over and covering part of an adjacent surface in sequence.
Collocations
- staggered overlap
- minimum overlap
- overlap joint
- overlap courses
Example sentences
- "Roofers must overlap each row of underlayment by at least four inches to ensure water sheds properly." Standard installation specification
- "The two-inch overlap between vertical cladding boards stopped wind-driven moisture from reaching wall studs." Modern siding installation manual
Memory hook
LAP ONE OVER THE OTHER so rain glides right off. Layer one over another.
When not to use
Do not confuse overlapping with placing boards end-to-end flush (butt jointing); overlapping requires one sheet laying over top of another.
Fun facts
- In traditional Japanese temple architecture, heavy ceramic roof tiles overlap without a single nail, held firmly in place by exact interlocking curves and gravity!
Related words
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