A FEW WORDS IN DEFENSE OF TIN ROOFS

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REPAIRING METAL ROOFS

There's one cardinal rule to remember when doing tin-top patching: Some metals, if placed in contact with certain others, can generate an electrolytic reaction that will result in rapid corrosion. To avoid that nasty possibility, be sure to patch copper roofs with copper, tin with tin, and so on.

If portions of the roof are badly damaged, you can remove the injured panels and replace them with new material, but be careful not to harm the adjoining healthy sheets when you're pulling the nails. Be sure to use neoprene-gasketed nails for the new application: They're specifically designed to prevent leaks. Drive your nails in at the high points of the corrugation . . . not in the valleys. (Or, insert neoprene-gasketed "drill screws" with a power drill to provide a watertight seal.)

If there appears to be any leakage through the existing nail holes, squeeze a dab of silicone caulking around and under the railheads before you whap them back down. (Leaking seams may also be caulked.)

Soldering is an effective method of mending splits and holes in a metal roof (except in aluminum). Solder tin and galvanized steel with rosin flux, and copper with acid flux. Be sure to heat the metal sufficiently to avoid getting a weakling cold joint, but use an iron to prevent temperatures from going too high.

If your roof doesn't have flashing in the appropriate places, you'll need to add it. For aluminum roofs, use .024" aluminum flashing material. For galvanized steel, use a matching metal, but in a thickness one gauge heavier than the roofing itself. Place flashings in the valleys, at the eaves and hips, and—of special importance—around chimneys. (Check with your local building-supply house for ready-made valley sheets and other flashing materials . . . or—if you have the necessary tools and skills—you can cut and bend them yourself.)

LIGHTNING, LIGHTNING,GO AWAY . . .

Too many metal-topped houses aren't properly grounded to prevent damage from lightning. Grounding will provide a path for the electrical current of a lightning strike so that it will bypass the house and enter the earth, where it can do no harm. If your home is not properly grounded, the lightning can easily pass through the structure, perhaps blowing out the electrical system or causing fire and personal injury.

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