headlap

headlap

In the lapping of roofing shingles, the shortest distance between (a) the lower edge of an overlapping shingle and (b) the upper edge of the lapped unit in the second course below.
References in periodicals archive ?
GS's valuable manufacturing expertise and vertical integration capabilities with respect to dry felt, fiber glass mat, and headlap and colored granules, are key to this acquisition and should help us significantly.
Elk Prestique Grande hybrid shingles with the signature High Definition(R) look are made with a patented new VersaShield(R) XP(TM) headlap technology.
An adjustable headlap feature allows equal course spacing, eliminating horizontal cutting during installation.