May, 2008

Understanding Rigid Flashing

Proper flashing relies on a few simple rules.

By Gary Katz

I remember my first home. I didn’t know much about flashing back then, so when I framed and sided the fireplace chimney, I ran T111 right down on to the roof sheathing. A knucklehead job like that might have squeaked by for a year or so if the chimney had been on a gable end wall, but it wasn’t. The chimney was directly against the eave line. Rain ran right up against it. Snow was even worse. It piled up high against the siding. The first winter, the roof leaked straight down the face of my stone mantelpiece.

I tried every type of caulking I could to stop the leaks, but nothing worked. Finally, I cut through the siding, ripped up the shingles, and installed a proper counter- flashed cricket. To learn the technique, I had to find a friendly roofer—an oxymoron in the town where I lived.

For years, I’ve been too embarrassed to tell that story. But after hearing similar stories from countless carpenters and contractors, and having seen even worse failures due to improper flashing, I’m no longer embarrassed by mistakes. In this business, we’re used to learning the hard way, hopefully the first time.

But today, we can’t afford to learn from mistakes. One mistake can ruin a reputation, to say nothing of future financial security. It’s much easier to learn the easy way—read journals and magazines, visit web sites, attend seminars, and learn about the latest materials and installation techniques.

And this is applies to building product professionals, too. Believe it or not, flashing is one subject that has changed a lot in the last 15 years.

As the industry slows down, customers will need a competitive edge more than ever. There’s nothing more valuable for lumber dealers to provide than solid education.

Two Simple Rules for Proper Flashing

1. FLASH WINDOWS AND DOORS

Window manufacturers require flashing at the head of every window and door. In addition, exterior trim manufacturers require flashing on all horizontal and raked surfaces, and that means window aprons on picture-framed trim, too.

2. FLASH ALL HORIZONTAL AND RAKED SURFACES

Only fire is more destructive to wood than water. Protect bandboards, water tables, dormer walls, and eaves with formed flashing, step flashing, and counter flashing. Solid copper is a good choice if it fits in the budget.

Flashing Materials
[A] Galvanized steel has been the most common flashing material, but steel interacts with concrete and fiber cement siding. Steel isn’t always the best choice today.

[B] PVC is perfect for sill pans and for separating aluminum thresholds from concrete slabs, but it’s not always the best choice for exposed flashings.

[C] Hybrid: York’s Soleil, a copper/aluminum lamination, costs a fraction of what solid copper does and can be installed with the copper exposed or reversed, in contact with concrete or treated lumber.

GARY KATZ, with nearly 40 years experience in the industry, is a contributing editor to Fine Homebuilding magazine, a frequent contributor to the Journal of Light Construction, and produces the Katz Roadshow—Carpentry Clinics at lumberyards all over America. To learn more, visit his web site: www.GaryMKatz.com.