Things to know about Traditional Double Lock Standing Seam roofing
We use G-90 26 gauge galvanized steel or plain copper. The roof pans are made in 10′ lengths. Any pan run that is longer than that will have a horizontal seam in it. The most economical pan width is 20.75″, and that is generally the size you see on old farm houses and barns. We try to stay with that unless we are forced to make changes to accommodate dormer valleys and overall symmetry of the roof.
The pan seams are folded over twice on the roof after the roof pans have been secured to the deck. The final seam height is about one inch. The seams are folded with tools made for that purpose, and will show tool marks as well as slight fluctuation in seam height. The horizontal seams, where they occur, are simply hammered flat with a hammer. At the ridge, the standing seams are hammered over flat to the roof so that the ridge cap can be installed over the hammered down seams. All of these methods of installation leave tool marks in the metal and give the roof a distinctly “old” look when it is completed. It is important to understand that the roof will not have the perfectly straight, seamless effect of contemporary metal roofs. It will have some dings and lumps and tool marks.
The term “G-90″ refers to the amount of zinc galvanizing on the steel. In this case, it means there is no less than .9 ounces of zinc per square foot of steel sheet. That is the heaviest coating available on 26 gauge steel. The metal can be left unpainted for 10 or so years, but should eventually be painted to inhibit rust. A galvanized steel roof that is well vented and kept painted will last indefinitely.
The advantages of this roofing over modern metal roofs:
Every piece is custom made in our shop for the job. The parts don’t “snap” together like the typical roll formed metal roof. It takes skilled men to install the roof, and the most common failure points(flashings at roof penetrations)are soldered, not screwed and caulked together.
All flashings and cuts are soldered together using metal parts that are custom made for each particular situation. There are no ”one size fits all” copings and flashing boots.
The disadvantages of this roofing over modern metal roofs:
The steel is of lighter gauge. Today’s roll formed roofs can be made of heavier gauge metal since there is very little working of the metal on site. They mostly snap together with caulked and riveted joints at flashings and other roof penetrations.
The roof is plain galvanized steel and does not have the added protection of a factory applied paint film.
By Brian Black