Metal Roof Chimney Flashing

Metal Roof Chimney Flashing

Boral Roofing’s Wakaflex® Roll Flashing is the best choice for chimney flashings, skylight flashings, pipe flashings, side wall flashings, head wall flashings, roof to wall flashing, step flashing, solar flashing, flashing roof vents, and many other flashing applications. Wakaflex is a lead-free substitute flashing for tile and metal roofs to help prevent leaks. Unlike copper, steel or aluminum metal flashings, Wakaflex is extremely flexible and stretchable to flash complex shapes and requires no special tools or welding. It is self-welding for easy installation even for tricky details. If you have a problem with a leaking flashing, Wakaflex may be the solution you need to fix that leak. Wakaflex is non-toxic and is a durable choice for a green universal flashing for the following roof applications: Chimney Flashing, Skylight Flashing, Flashing Plumbing Pipes, Pipe Flashing, Flashing Vents. Solar Flashing, Step Flashing, Roof to Wall Flashing, Side Wall Flashing, Head Wall Flashing, Apron Flashing, Skirt Flashing, Flashing Apex, Abutment Flashing, Saddle Flashing
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Metal Roof Chimney Flashing

Counter-flashing (or cover flashing, cap flashing) is a term used when there are two parallel pieces of flashing employed together such as on a chimney, where the counter-flashing is built into the chimney and overlaps a replaceable piece of base flashing. Strips of lead used for flashing an edge were sometimes called an apron, and the term is still used for the piece of flashing below a chimney. The up-hill side of a chimney may have a small gable-like assembly called a cricket with cricket flashing or on narrow chimneys with no cricket a back flashing or back pan flashing. Flashing may be let into a groove in a wall or chimney called a reglet.
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Metal Roof Chimney Flashing

In addition to the saddle, you’ll need the following sheet metal parts (see Figure A): Front base flashing. Order about 12 in. more than the width of the chimney. Some lumberyards stock a “dormer flashing” that will work in this location. You may have to adjust the angle by bending it to match your roof slope. Prebent step flashing, 8 x 8 in. Roofers call these “shingle tins”. You’ll need one for each shingle along the edge of the chimney plus a few extra. Most lumberyards stock these. Front cap flashing and side cap flashing. Some sheet metal shops stock a flashing for this purpose, but you’ll probably have to have it made. Measure at the front of the chimney from the roof to the third mortar joint and add about an inch to determine the height you’ll need. The shape is relatively simple, so you could buy flat sheet metal, called “coil stock,” and bend these yourself. Back cap flashing. This flashing is identical to the front and side cap flashing.
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Metal Roof Chimney Flashing

In this article, we’ll tell you how to order new flashing and install it on a brick chimney. Our roof has asphalt shingles, but the procedure is the same for wood shingles. Slate and tile roofs require special flashing techniques that are best left to the pros. Flashing a chimney is an advanced DIY project. For starters, you have to be comfortable working on a roof. Then you have to measure, cut and bend sheet metal to fit precisely around the chimney and layer all the parts so they shed water. Even so, if you’re handy with tools and carefully follow our instructions and diagrams, you’ll be able to flash your chimney in a day, and by doing it yourself, save hundreds of dollars.
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Metal Roof Chimney Flashing

Metal flashing materials include lead, aluminium, copper, stainless steel, zinc alloy, other architectural metals or a metal with a coating such as galvanized steel, lead-coated copper, anodized aluminum, terne-coated copper, galvalume (aluminum-zinc alloy coated sheet steel), and metals similar to stone-coated metal roofing. Metal flashing should be provided with expansion joints on long runs to prevent deformation of the metal sheets due to expansion and contraction, and should not stain or be stained by adjacent materials or react chemically with them. An important type of potential chemical reaction between metal flashing materials is galvanic corrosion. Copper and lead cannot be used in contact with or even above aluminum, zinc, or coated steel without an increased risk of premature corrosion. Also, Aluminum and zinc flashing cannot be used in contact with pressure treated wood due to rapid corrosion. Aluminum is also damaged by wet mortar and wet plaster. Salt spray in coastal areas may accelerate corrosion. so stainless steel, copper, or coated aluminum are recommended flashing materials near salt water.
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Metal Roof Chimney Flashing

Making sharp, straight bends in sheet metal is tricky unless you have access to a tool called a sheet metal bending brake. Even then, you need experience to bend complicated shapes. That’s why we’re recommending that you order your chimney flashing from a sheet metal fabricating shop. Large roofing companies often have their own sheet metal shops and are the best place to buy the chimney saddle and flashing; they’ll know exactly what you need. Otherwise, check the Yellow Pages under “Sheet Metal.” We used 26-gauge galvanized sheet steel for our flashing and saddle, but prefinished steel or copper are other possibilities.
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Metal Roof Chimney Flashing

A.Carl Hagstrom responds: The evenly spaced ridges of the roofing profile present a real challenge. When visualizing a flashing strategy for the down-slope face of the chimney, picture the plane of the roof at the top of the ridges, not at the lower, flat portion of the roofing profile. At the sides of the chimney, extend the flashing out past the nearest formed ridge, fold it over the ridge, and then fasten through the flashing at the high point of the ridge with neoprene gasketed roof screws.
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Metal Roof Chimney Flashing

A.Carl Hagstrom responds: The evenly spaced ridges of the roofing profile present a real challenge. When visualizing a flashing strategy for the down-slope face of the chimney, picture the plane of the roof at the top of the ridges, not at the lower, flat portion of the roofing profile. At the sides of the chimney, extend the flashing out past the nearest formed ridge, fold it over the ridge, and then fasten through the flashing at the high point of the ridge with neoprene gasketed roof screws.This goes against the roofing manufacturers’ recommendations to place screws in the flats of the roofing, but I’ve used this approach with success. Login or Register to read the full article.
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Before you do anything, get your ladder, roof brackets and safety harness set up so you can work safely and efficiently on the roof. Then measure the chimney and order the saddle and flashing parts (see “How to Buy Chimney Flashing,”).
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Copper is an excellent material for flashing because of its malleability, strength, solderability, workability, high resistance to the caustic effects of mortars and hostile environments, and long service life (see: copper flashing). This enables a roof to be built without weak points. Since flashing is expensive to replace if it fails, copper’s long life is a major cost advantage. Cold rolled (to 1/8-hard temper) copper is recommended for most flashing applications. This material offers more resistance than soft copper to the stresses of expansion and contraction. Soft copper can be specified where extreme forming is required, such as in complicated roof shapes. Thermal movement in flashings is prevented or is permitted only at predetermined locations.
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Once a starter flashing is put in place, we can then install a gable flashing against gable rake, with a half an inch spacing. Note, that a gable flashing has to overlap the drip edge flashing (shown above) at the edge.
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How to Find Your Roof Slope Find the slope of the roof. Label one edge of a 2-ft. square scrap of plywood or cardboard “roof” and lay the labeled edge against the roof. Draw a level line at least 12 in. long on the plywood and label the line “run.” Measure 12 in. along the “run” line and make a mark. Use a framing square to draw a square line from this mark down to the edge of the plywood labeled “roof.” Label this line “rise.” Measure the length of the line labeled “rise” to determine the slope, expressed as inches of rise for every 12 in. of run. In our case, the roof slope is 6 in. of rise for every 12 in. of run. Find the “run” of the roof slope Find the “rise” of the roof slope
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Most chimneys have a small rooflike structure behind them, called saddle (Photo 6), that diverts snow and water to both sides of the chimney. Whether your chimney has a wooden saddle covered with shingles, a sheet metal saddle or no saddle at all (like the chimney in this story), we recommend installing a new custom-made sheet metal saddle (Photo 6).
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Flashing may be exposed or concealed. Exposed flashing is usually of a sheet metal and concealed flashing may be metal or a flexible, adhesive backed, material particularly around wall penetrations such as window and door openings.
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We ordered all our 26-gauge galvanized metal flashing bent to the correct angles and dimensions from a sheet metal shop specializing in roofing. The shop did a great job. I dropped off the dimensions and three days later the stuff was ready to pick up. Even with the custom-made saddle, the flashing was inexpensive. In addition to the flashing and shingles, buy a roll of self-adhering roofing membrane (also called ice-and-water barrier), two tubes of polyurethane caulk, and a package of 25 drive-in expanding anchors from a home center or roofing store.