old slate and tile roofs have low-slope soldered-seam metal
roofs abutting or adjoining them. Theyre usually
found on porches, bay windows, mansard roofs, and two-story
additions and are most often made of terne metal pans,
and sometimes copper pans, soldered at their flat-lock
seams, hence the name soldered-seam, lock-seam, or flat-lock roofs.
best way to repair a leaking soldered-seam metal roof is
the same way flashings are repaired on slate or tile roofs:
the old metal is completely removed and then replaced.
When the old terne metal is removed, it should be replaced
with new terne-coated stainless steel or 20-ounce copper. 16-ounce copper will work too, but for the smaller extra
cost and the promise of a metal roof that can last a century
with little maintenance, the 20-ounce copper would be preferable
(and the stainless the most durable). It has become difficult
these days to find roofing contractors who can and will
do flat-lock metal roof work, and it is even more difficult
to find information or instructions on how to do this sort
of work, which is why we have included it in this issue
of Traditional Roofing.
flat-lock roof starts with a drip edge piece (see illustration
below). The field of the roof is then covered with metal
pans which can be various standard sizes, the most common
today is a pan 24" X 18".
flat pans are cut, the corners are snipped off at
a forty-five-degree angle, then two adjacent edges are
folded up and the opposite two adjacent edges are folded
down, the folds being 1/2" to 3/4". The pans
are fastened to the roof with cleats, these being made
of the same metal, approximately 1.5" X 2", with
a fold equal to the folded seam on the pan (1/2" to
3/4"). This fold is fit into the pan seam, and the
other end is nailed to the roof deck with two nails, then
folded over the nail heads. Two to three cleats are recommended
on the long side of the pan and one to two cleats on the
short side. The seam is then hammered down with a dead
blow hammer and soldered with 50/50 tin/lead solder or
other suitable solder. Roof protrusions such as vent pipes
are fit closely around the base with a pan, then a sleeve
is fabricated with a flared bottom that is riveted to the
pan and soldered in place.