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 ?
Elk Prestique Grande hybrid shingles with the signature High Definition(R) look are made with a patented new VersaShield(R) XP(TM) headlap technology.
Elk's Prestique(R) Grande shingle, featuring its patented VersaShield(R) XP headlap technology, has gained market acceptance in fiscal 2005.