How to Mortar a Chimney Cap

Incorrectly mortaring a chimney cap can result in a loose cap that shifts or separates from the chimney during strong winds. If a chimney cap shifts, rain, snow or even leaves can enter the chimney. Such moisture or debris can dampen a fire or block a chimney, causing potential fire hazards. Correctly mortaring a chimney cap ensures a secure mortice and lets the cap protect the entrance of your chimney from the elements.

Quickset mortar
Chimney cap extension
Mortar trowel
Bubble level
Cutting torch
Steel rebar

Instructions

- 1
  Apply 1/2-inch to 1-inch thick layers of quickset mortar around the chimney cap extension using a mortar trowel.
- 2
  Shape the mortar until it approximates the width and length of the chimney. Ensure the mortar remains tight against the chimney cap.
- 3
  Mortar to a height of 25 percent of the chimney cap, creating a level surface as indicated by your bubble level.
- 4
  Cut the steel rebar to the width of the chimney using a cutting torch.
- 5
  Lay one section of rebar alongside each edge of the chimney cap, surrounding the cap. The rebar will reinforce the mortar, protecting it against cracking or breaking.
- 6
  Mortar until it reaches approximately halfway up the height of the chimney cap using the mortar trowel. Continue shaping it, so it maintains the same width as the chimney. Allow it to dry for 48 to 72 hours.

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