The roofers lead (leed) is the
pattern of
shingles that the
roofer lays down to form the start of each
course. This relates mostly to
asphalt shingles, the most
common variety being the
3 tab, although it works for the heavier
architectural grade. The
wrapper on the
shingle bundle has instructions for laying 3 tab shingles, but the pattern produced by the
alignment of the spaces between the
tabs and the ends of the shingles produce an unsatisfactory finished product unless considerable care is give to
align each course with the one below. That pattern has each course offset to the one below by a half a tab's width. The
effect is that in every other course the slots line up and the visual effect is lines straight up the roof from eave to ridge. If one course is
misaligned it stands out like a
sore thumb and even
small variations of
butting adjoining shingles in a row will alter the spacing and hence the pattern produced. Pros call that lead the
homeowners lead.
Since
time is money in
construction, a
pro roofer wants to attach the most amount of material with the least amount of moving around on the roof. A pro roofer will start the shingle rows so that the alignment is offset to the row below by 1/3 of a tab. That doesn't sound like much difference, but the effect is that now the roof surface appears to have
diagional lines going from eave to ridge, and small variations in the spacing don't show up near as much. Also with the smaller offset the roofer can do more work each time he
repositions himself, therefore working faster. Check it out for yourself, look up at some roofs. There is also roofers lead (led), but that's
another node.