Check the mortar around the base of the chimney if the chimney flashing is pulling away from the roof. Though chimney flashing at the base of a roof chimney often pulls away due to the presence of moisture, it may also pull away due to cracks in the chimney mortar.
Remove any mortar that is cracked or crumbling in the chimney with a grout saw. After scraping out any damaged mortar, continue removing good mortar to a depth of 3/4-inch.
Spray the wall with a hose to clean out the mortar bits. Allow the wall to dry 24 hours before applying new mortar.
Mix a batch of mortar according to the manufacturer's instructions until it is paste-like and sticks to the trowel. Apply the mortar to the gaps in the brick until it sits evenly with the brick. Allow the mortar to dry to the touch and brush off the wall.
Place a tarp over the repaired chimney. Lift the tarp once every day and spray the mortar lightly with water. Leave the tarp for 72 hours before removing it.
Hammer the flashing so that it sits flat against the roof if the metal has warped. Apply waterproof sealant around the edges of the flashing with a caulking gun and allow the sealant to dry 72 hours to repair the flashing seal. Alternately, apply a flashing seal to the base of the chimney around the flashing, which applies with an adhesive backing and also creates a watertight seal.
Things You Will Need
- Grout saw
- Garden hose
- Cleaning brush
- Waterproof sealant
- Flashing seal
- If you have a full-length chimney that is pulling away from the side of the house, this can be a sign of serious structural issues with the foundation. The experts at This Old House advise that a leaning chimney is not something a homeowner should attempt to tackle alone. The house should be inspected for structural damage and the chimney should be fixed by a certified mason.