How to Repair a Chimney Crown

Lead Image for How to Repair a Chimney Crown
  • 6-8 hours
  • Intermediate
  • 450-700
What You'll Need
Thinset Mortar
Masons Cement
Water Sealant Paint

Chimneys are exposed to constant wear and tear from the elements and heat making it necessary to repair your chimney crown from time to time. The crown is the part that acts as the protector of the chimney, and you can easily repair it at home without incurring great expense.

Step 1: Concreting Cracks

If you do not want to make a new crown, you could simply fill up the cracks that are visible. Take some thin-set mortar from a pack and make a mixture using water, that is neither too lumpy nor too tight. Scoop it up with a trowel and put it in the cracks so that it fills them up entirely. Finally, level the surface of the crack with some more mortar and smoothen it by rubbing a flat piece of wood over the surface.

Step 2: Caulking

A good alternative to concreting is sealing or caulking up crown cracks. Clean up the cracked area and remove the rock pieces. Take some caulk or Sealfolex and apply it evenly over the crack and let it dry. This must be done by using a brush. This acts as a filler cum sealer that repairs cracks. Make sure that the cracks get filled up to a good depth and not simply on the surface. Wipe the excess caulk off using a wet rag.

Step 3: Detaching the Crown

In order to effect the necessary repairs, you need to take off the damaged crown. Cover the roof with a drop cloth so that it remains clean. Place the chisel in a position towards the edge of the crown, away from the flue, and gently hammer on it so that the concrete breaks. The pieces that are broken can be kept in a bucket or container.

Step 4: Mixing Mortar

Mix two parts mason’s cement with one part gravel. You have to take more of the amount if your chimney is larger but maintain the same ratio. Make sure that there are no lumps in the dry mixture itself before adding the required water. Next add water in small amounts till you see that the mix retains it, to the point of not being too flowy. Add some bonding agent, about a cup and mix well.

Step 5: Final Repairs

Take up this mixture of concrete and apply on the chimney around the flue, in place of the detached crown. If the flue of the chimney is about 6 inches from the top, the crown must be made 4 inches from the flue top. If the flue is at a height less than 6 inches, the crown should be built 2 inches from the flue top. See if the cement holds to the chimney body and then apply more of the mix. Spread evenly using the trowel. Now move the trowel in a chopping motion so that the mortar binds the crown more firmly. This also eliminates the chances of forming air bubbles that can make the crown hollow. Smoothen the mortar and see that the crown is sloped away from the place of the flue. Finally, let the crown dry for a day and then paint it with a water sealant like Crown Coat to make it waterproof; two coats applied with a brush shall be sufficient.