How to Repair a Cement Chimney Crown

Written by edwin thomas
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How to Repair a Cement Chimney Crown
Chimney crown cracks open the roof to leaks. (Jupiterimages/ Images)

A solid chimney crown is made from steel-reinforced concrete, but unfortunately many chimney crowns are not made to this standard. All too often, the crown is essentially a pile of cement leftover from the construction of the chimney. As moisture penetrates the porous surface of the cement, the crown cracks open. Because of the weaker structure, those cracks must be dealt with promptly, lest the chimney crown fall apart and open the roof of the house to leaks.

Skill level:

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Things you need

  • Wire brush
  • Caulking gun
  • 1 tube of polyurethane caulk
  • Plastic scraper

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  1. 1

    Scrub a crack in the chimney crown with a wire brush. This both removes debris from the crack and loosens any crumbling cement that might prove a problem in the immediate future.

  2. 2

    Fill the crack with polyurethane caulk utilising a caulking gun.

  3. 3

    Pull a plastic scraper across the top of the crack, which will both push caulk down into the recesses of the crack and scrape off excess caulk at the same time.

  4. 4

    Repeat Steps 1 to 3 on the next crack, continuing until all the cracks are sealed with polyurethane caulk.

Tips and warnings

  • If the cement cap has crumbled and left the brickwork exposed, it must be replaced. The best solution is to hire a professional and have a steel-reinforced concrete crown installed, but a more immediate solution is to coat the top of the crown with a brushable sealant, such as CrownSeal.

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