Photo by: Patrick McCombe
When my roofing company flashes a chimney, we save time on the roof and make our lives easier by bending the various flashing parts ahead of time on a metal brake. We use a brake rather than bend by hand because it gives the flashing crisp, straight bends that look and perform better than the somewhat wrinkly bends of hand-formed chimney flashing.
When I make flashing parts, I prefer to use our company’s spacious metal shop. The room’s bright lights and large worktable make it easier to move and lay out the pieces. When you’re looking for a space to lay out and cut sheet metal, look for a place large enough to allow you to rotate the longest lengths of flashing that you’ll be using. It’s also smart to spend some time setting up a good-size worktable, even if it’s just a scrap of plywood on sawhorses.
Our metal shop has a large stationary brake, but we also use portable brakes that we carry in the back of our vans. The layout and bending techniques are the same for both tools. The least expensive 8-ft. and 10-ft. portable brakes common on roofing and siding jobs cost hundreds of dollars, but they are available at rental yards and many home centers for about $50 per day. If you’re bending only smaller pieces, you can buy a smaller brake for about $300.
We use 16-oz. copper for most of our residential flashing work. We like copper’s malleability, and we like that it’s easy to solder. Prepared correctly, copper flashing shouldn’t need attention for decades. We generally pay about $150 for a 3-ft. by 10-ft. sheet, although the price fluctuates.
When you’re bending any type of flashing, the first step is to cut the material to length and width. Our shop has a large shear that I use for cutting the stock to width, but you also can use snips. I like aviation snips for hand-cutting because they require less effort than traditional tin snips. Use care when handling the stock, because cut edges can be extremely sharp. Make the pieces longer than you need, and cut them to exact size on the roof.
Once the piece is cut to size, I lay out the various bends on the flat stock. I mark the bends by measuring from one side of the flashing only so that any slight discrepancy in the width will be hidden by a hemmed edge. Some flashing profiles involve flipping the flashing stock multiple times for bends in opposite directions, so I mark the bends on both ends of the flashing with a hammer and a dull punch. The resulting dimple shows on both sides of the stock, saving time and reducing the number of mistakes.
Once I’ve marked the stock, I plan the order and the direction of the bends so that I don’t crush or distort the flashing piece while I make additional bends. You can see how the pieces go together and how our company flashes a chimney in "Time-Tested Approach to Chimney Flashing