Roof leaks often occur where a roof’s surface meets a chimney. The culprit is usually flashing that was mistakenly installed or has become worn to the point of leaking. Proper chimney flashing includes 2 layers. Base flashing secures into the roof; cap flashing overlaps the base layer and also contains an L-shaped top that is inserted into grooves which are cut at the chimney’s mortar. Constructing a chimney saddle, or cricket, which directs water away from the chimney because it flows down the roof requires specialized tools and expertise, and is probably best outsourced to a steel shop.
Calculate the slope of the roof. Hold a 2-foot-by-2-foot piece of plywood or cardboard vertical to the roof. Put a 2-foot level throughout the plywood and draw a line across it. Mark a spot at 12 inches over the line. Hold a framing square over the line and draw another line from the mark to the base of the plywood. Measure the length of the second line. The slope of the roof is expressed since that measurement of growth for each 12 inches of run. Measure the width of the chimney. Provide the width and the slope measurements to a metal shop to produce the chimney saddle.
Pry up the shingles, flashing and roofing membrane across the chimney using a pry bar. Inspect the roof decking and replace any water-damaged sections with granite.
Seal the region around the chimney with 12-inch-wide strips of water and ice barrier. The obstacle should lap 4 inches up the front of the chimney and 8 inches up the back. Install shingles around the base of the chimney.
Cut a piece of pre-bent base flashing, using tin snips, to the width of the base of the chimney plus 8 inches. Starting in the top left corner of this flashing, then create a cut at 45 degrees until you arrive at the bend at the flashing. Repeat the process in the top right of this flashing piece.
Fit the base flashing against the base of the chimney and bend back the sections above the 45-degree cut till it meets the chimney. Bend back the region under the cut till it meets the roof. Nail the flashing into the surface of the roof with 1-inch galvanized roofing nails put every 6 inches.
Make a 11/2-inch cut into a part of pre-bent step flashing across the crease. Put the step flashing across the side of the chimney and also bend the section above the cut so that it wraps around the front of the chimney. Nail the step flashing into the roof. Continue installing step flashing up each side of the chimney, overlapping each piece by 4 inches.
Put the chimney saddle against the back of the chimney so that it overlaps the step flashing on the side of the chimney. Nail it in the roof deck, placing nails ever 6 inches.
Cut 1-inch deep grooves into the next mortar joint on the front of the chimney with a grinder outfitted with a dry-cut diamond blade. Make comparable cuts on the faces of the chimney, moving up the cuts to the upcoming mortar joint in order that they stay at least 4 inches above the step flashing.
Cut a piece of cap flashing into the width of the chimney and also 8 inches. Drive the L-shaped top of this cap flashing into the grooves in the front of the chimney by holding a sheet of scrap timber against it and striking it with a hammer. Bend the cap flashing across the side of the chimney. Drill a hole through the section of cap flashing which you bent across the side of the chimney and into the brick with a 3/16-inch piece. Attach it into the chimney working with an expanding plastic anchor.
Cut bits of cap flashing to fit the grooves at the side of the chimney in order that they overlap by a minimum of two inches. Drive every single piece’s L-shaped top into the groove and fasten it with at last one expanding plastic screw and anchor. Put cap flashing across the back of the chimney, overlapping the saddle by at least 4 inches.
Apply a bead of polyurethane caulk across the cut mortar joints, sealing the joints between the cap and the mortar.