Chimney crowns are very important to the integrity of your chimney; an improperly installed chimney crown could cost you thousands of dollars in repair work down the road. Using the right materials, following the correct procedure, and consulting with a professional will help you to construct a chimney crown properly. The chimney crown helps to prevent the mortar in between the bricks on your chimney from eroding away in rainfalls.
Removing your existing chimney crown is often where mistakes occur. You do not want to damage the brick on the chimney or the chimney flue itself. To prevent incidental damage from occurring, chisel off the existing crown starting from the edges and working your way in. Work carefully and wear eye and hand protection to protect yourself from flying bits of concrete.Similarly, remember that you are working likely on a roof or a ladder and are up in the air. Follow all building codes in your area and never do anything that you do not feel comfortable doing; this may lead to injury.
We never recommend using mortar to construct your crown. Mortar is very vulnerable and will erode away quickly. Cement crowns will outlive crowns constructed from mortar every time. Making a consistent and appropriate concrete mixture is important to having a crown that will not easily be damaged by water or freezing and thawing. Although you should follow the directions on the cement that you buy exactly, usually you must mix all of the dry ingredients prior to adding any water. Be aware that when applying the cement to the chimney, air pockets inside the cement will prevent it from standing as strong as possible.
You are going to need to set some steel forms on the chimney to fill up with cement. We recommend installing a 2″ or 3″ drip edge crown, which means the steel forms allow for the chimney crown to be constructed with an extra two or three inches on each side of the chimney. This prevents water from dripped directly down the brick on your chimney. Fill the steel forms up completely with cement to ensure a very flat top. A top that is not completely flat will allow water to pool which will catalyze your chimney crown’s deterioration.
After your chimney crown has had time to cure according to manufacturer’s instructions, waterproofing your chimney is a wise investment. Spending less than fifty dollars to waterproof your chimney crown will prevent damage in the future that will cost much more to repair. When water is able to sit directly on top of the crown, it will expand and contract as it freezes and thaws and slowly but surely create cracks in the crown. These cracks can be filled by specialized chimney crown repair products, but if the cracks get too deep then often times the crown must be completely replaced. Such a repair can costs thousands if done professionally. Waterproofing your chimney crown prior to such damage is always the best decision.