A
History of Metal Roofing
The use of
metal for waterproofing roofs goes back to the Roman Empire, when lead
was used extensively in roofing and plumbing. In fact, the word plumber
comes from the Latin word for lead - plumbus. Lead, and sometimes copper
or zinc, continued for centuries to be used for roofing throughout
Europe, Asia and North Africa, and was carried to North America in
colonial times. American metal roofers, in the early 1800's, began
experimenting with tinplate, which was a less expensive alternative to
lead, copper, and zinc. Tinplate was a new material then, and old
crafting techniques needed to be updated to properly fabricate this
material. New tools were invented and tinplate sheets were made 24
inches wide by 60 inches long, a newly established standard for the
roofing industry. The sheets were joined by bending up the sides of each
sheet 3 inches to form a key. Then the 2 keys of abutting tinplate
sheets were folded over twice to form a 1 inch standing seam and lock
the 2 plates together. Metal strips fastened to the roof frame were
folded into the seams to hold the sheets onto the building, and lead
solder was used with wood rosin flux to completely seal any remaining
voids. Rust was a major drawback to tinplate roofing, but the onset of
corrosion was slowed down by increasing the lead to tin ratio in the
tinplate alloy. However, as rust never sleeps, paints made from fish oil
or linseed oil were developed to protect metal roofs. These protective
paints proved very effective if re-applied on a regular basis.
By the mid
1900's, corrugated, galvanized, metal sheets were mass produced and
became a very popular and economical alternative to tinplate for
industrial, agricultural, and commercial roofing. Instead of being
folded together, the corrugated sheets were overlapped and then
fastening screws were drilled through the overlapping sheets to anchor
them onto the roof frame.
In the past 30
years, coil stock has been formed into corrugated sheets for use in
roofing. This stock comes in a variety of factory applied finishes which
protect the metal from rust and provide lots of eye appeal. Instead of
lead solder, advanced caulks and sealants are used to seal laps, and
rubber grommets are used to seal the fasteners.
