Building a chimney crown

Even if a chimney crown may seem as an insignificant part of the chimney, it helps prevent things like rain or small animals enter the chimney and also helps remove the smoke from the chimney more efficiently. When building a chimney crown you must follow a few simple steps.

Tools and materials needed

  • 2×4-inch board
  • 1×6-inch board
  • Nails
  • Hammer
  • Miter box
  • Protective goggles
  • Gloves
  • Brick chisel
  • Hammer
  • Wire brush
  • Saw
  • Wood Screws
  • Drill
  • Screwdriver drill blade
  • Load binder or band clamp
  • Bench saw

Old mortar removal

Before replacing the existing crown, you must remove the mortar.

Use a hammer and chisel to break off the mortar. Clean the area of any debris after you are done.

Frame construction

Use 2×4 boards to construct a frame. Rip a board with a 15 degree level and then nail it to a 1×6 board. The 2×4 bottom has to be flush with the frame bottom. This piece must be cut into 4 section but allowing the 2×4 to fit into place around the chimney bricks at the top in such a way to create a 2-inch thick cap with a 1 and a half inch overhang. Drill screws  into the wood pieces at each corner.

Set the frame

Set the frame on the chimney brick and reinforce it with a load binder or a band clamp. If you see any gaps, use duct tape to seal them before you apply the mortar. This way the concrete won’t crack as the flue heats and then expands.

Expansion joint

Create an expansion joint placing corrugated cardboard around each flue and keeping it in place with duct tape. This prevents the concrete from cracks when the flue will heat. Use oil  inside the form surface to avoid it from sticking when stripped. Don’t get oil on the brick surface or it will not bond to the concrete.

Apply concrete

Use small aggregate and mix concrete. Pour water into the mix and then apply 1 inch of concrete into the form. Put rebar into the form leaving 2 inches sticking out. Fill the form with concrete and then smooth and tamper it.

Remove form and caulk

Remove the form and then apply seal to the flue joints with caulk. Waterproof the crown.

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