If you find water stains on your fireplace ceiling, it’s likely time to replace the chimney flashing. Chimney flashing is an aluminum piece commonly installed on shingled roofs at the chimney stack edges to prevent water from getting into where chimney and roof connect. Leaks occur when the sealant at the chimney and roof connection deteriorates. Here are some tips to replace chimney flashing on a shingled roof.

Prepare the Roof

For this project, you need:

  • an extension ladder
  • a safety harness
  • a waste bin
  • garden hose
  • a chisel
  • a hammer
  • a wire brush
  • putty knife or caulking gun
  • a pry bar
  • replacement shingles
  • polyurethane caulk
  • galvanized roof flashing nails
  • replacement flashing 

Keep a waste bin handy for disposing of roofing material. Though you can cut flashing yourself, ordering it customized makes the job easier. Before you replace the flashing, take measurements around the chimney to get the right size, and order the replacement from a metal shop.

Remove Old Chimney Flashing and Shingles

Set the ladder on flat, even ground, placing the top rung three feet above the roof edge. Wearing safety gloves, slightly loosen the shingles from the adhesive, scrape the old adhesive with a chisel, and remove nails, but not the good shingles.

Pull off the tar underlayment and old flashing with the pry bar, and clean debris with the wire brush or small broom to remove particle that could interfere with sealant. For chimneys with counter flashing, scrape the mortar until you reach the metal flashing, and remove the nails.

Install the New Flashing

Lay the base flashing across the chimney edge, and on top of the shingles folding the tabs on the roof. Nail the sides into the chimney, but not the roof. Install the step-flashing on the bottom edge of the chimney, and replace shingles on the lower course. Place the next piece of step-flashing with overlap on the next shingle course, and repeat for the remaining pieces of flashing.

Insert the top flashing in place securing it with nails on the chimney folding tabs. Lay the last course of step-flashing and shingles. Set the L-angle of the counter-flashing in the empty mortar space so it overlaps across the top of step-flashing, and mortar the chimney joints.

Caulk each joint of the flashing with a putty knife or caulking gun, and let dry.Test the roof for leaks by spraying a stream of water with a garden hose on the area. Get someone to stand inside, and watch the chimney area for leaks as you spray.

Replacing chimney flashing yourself will save you money. However, working on roofs requires the proper safety procedures. If you have a high roof, or the repair didn’t stop the leak, contact a roofing company, such as McCullers Roofing