How To Fix Spider Cracks In Your Chimney Crown

An important aspect of home maintenance is keeping your chimney in good condition; after all, if your chimney is unstable, the whole of your roof could be at risk of damage.  A common problem with brick chimneys is cracking in the cement crown.  The crown is designed to prevent water from penetrating the chimney and getting into the house.

If you're a competent DIYer, you might like to tackle this project yourself.  Alternatively, ask a professional roofer to carry out the work for you.  Here are some tips on how to correct the problem.

What you'll need

  • crown sealer
  • chimney water repellent
  • garden pump sprayer
  • stainless steel chimney cap
  • paint brushes
  • disposable gloves
  • stiff, nylon brush

You can get everything you need from good DIY and hardware stores.  Choose a dry, calm day for this project and always ask someone to foot your ladder for you if you're working at height.

How to do it

  1. Start by getting rid of any debris and loose caulk from the chimney crown.  You can do this by scrubbing all around the crown with a stiff, nylon brush.  
  2. Next, put on your disposable gloves and start by grabbing a handful of sealant and wiping it onto the cracked chimney crown.  Use your fingers to push the sealant well down into the cracks and into the seam between the crown and the chimney bricks.  
  3. Use a paintbrush to 'stroke' the sealant while it's still wet so that any low or high spots are evened out.  The end result should be a smooth surface.  
  4. When the first coat is touch-dry (after about half an hour or so), apply a second coat with the brush.  
  5. Now fill the pump sprayer with water repellent.  Begin at the bottom of the chimney and spray all the brickwork, right up to the top.  Allow five minutes or so for the first coat to dry, and then apply a second coat using the same method.  
  6. Next, install the flue cap.  This keeps water out and prevents birds and pests from setting up home inside the chimney.  To do this, set the flue cap over the clay liner (chimney pot) that you'll find already in place on top of the chimney and secure it with the screws provided with the cap.  Be careful not to over-tighten the screws, as this can crack the clay liner.

In conclusion

Keeping your chimney crown free from cracks is a relatively straightforward project that you can carry out yourself if you have good DIY skills.  It's a good idea to check your chimney after the worst of the winter weather has passed, and after spells of very high winds.