Tips to maintain, install metal roofing offered

Metal roofing, while adding a unique or period touch to your home, often brings up questions regarding maintenance and installation.

As far as painting goes, terne (copper and tin plate), should be painted as soon after application as conditions will permit with a red iron-oxide, linseed-oil vehicle primer to prevent corrosion. This paint, which is brush-applied, is very slow drying with a 72-hour drying time. This is followed with a compatible linseed-oil finish coat.

In the old days, folks just used two coats of the red iron-oxide primer, which is the reason many of us picture old metal roofs as red. Today, the compatible finish is available in a variety of colors. Depending on environmental conditions, expect to repaint about every eight years.

Some of the metal shingles manufactured today are made from galvanized steel, the same way they were at the turn of the century. Like terne, galvanized steel should be painted. This smooth, slick and shiny surface must be etched or roughened up before paint will adhere to it properly.

Today, most of the major paint companies sell self-etching primers for use on new galvanized panels.

Terne-coated stainless steel (TCS) blends the best of yesterday and today: the durability and permanence of terne in a virtually maintenance- and corrosion-free product. TCS is type 304 stainless steel that's coated on both sides with a terne alloy that's 20 percent tin and 80 percent lead. It's considered self-healing because the terne coating is anodic to the stainless steel.

In other words, if it is scratched, the terne will act sacrificially to protect the base plate. Because of the way it resists corrosion, TCS is a good choice for severe marine or industrial climates. Under most conditions, its unpainted surface will weather to a warm gray.

Another self-healing alloy used in the manufacture of metal roofing is Galvalume, a sheet-metal product with an aluminum-zinc alloy coating. This material also requires no paint and, if left to its own devices, will weather and eventually look like dark zinc. It's also available in a variety of factory-finished colors.

Fortunately, installing metal shingles isn't much different from installing any other composite single roof.

Any roofing contractor will be able to do it. So should any of you do-it-yourselfers who aren't afraid of heights and are willing to tackle a roofing job. Basically, most metal shingles interlock and are secured to the roof with two nails driven through a nailing flange.

Although installing a seamed metal roof is a bit more complicated, it can be done by a sophisticated do-it-yourselfer if it's a pretty straightforward job.

A lot of the craftsmanship that used to go into this type of installation has been replaced by machinery.