Chimneys
Mortar chimney caps are sometimes vulnerable to cracks along
the joints because the mortar shrinks, causing the joints to open.
In particular, lime-based mortar decays over time and may crumble. To repair
cracked mortar on your chimney cap or between bricks, you'll need:
Minor cracks and the joint between the flue and the cap can be sealed with
masonry caulking compound.
If the cap is crumbling, you'll have to chip out the old, deteriorating mortar,
using a ball-peen hammer and a cold chisel as shown at top left. Be sure to
wear gloves and goggles. Brush off any loose debris. Then, as shown at bottom
left, apply a new layer of ready-mixed mortar, using a trowel. Slope it away
from the flue so rain will drain off properly. Keep the mortar damp for 4
days to allow it to cure.
To repair mortar around the bricks, remove the old mortar
and pack cracks with new, ready-mixed mortar.
To renew flashing seals, chip out the old mortar. Caulk along the edges of
the flashing and caulk the joints between the flashing and the chimney.
