![]() ![]() Wood is not only flammable, but it will soak up moisture which will expand when it freezes causing the crown to crack. When building the bond break don't use plywood or other similar materials. Second, it allows the masonry walls and the concrete crown to expand and contract at different rates, reducing the possibly of them cracking. First, without the barrier the cement will just run down the chimney structure filling the airspace between the flue and the masonry walls. Then lay sheet metal or cement board across the metal supports to form a thin bond break between the chimney crown and the masonry walls. Use steel support bars to form a grid pattern from one side of the masonry wall to the other. Since the concrete and the flue will expand and contract at different rates, this expansion gap will prevent damage to both the flue tile and the crown. Silicone sealant should be added to the 1/4'' separation to prevent water damage.Ĭeramic wool insulation makes a great compression material. ĭuring construction the flue should be wrapped with a compression material to allow a 1/4'' separation between the concrete crown and the flue tile. ![]() The concrete crown should not come into contact with the flue. There is very little mortar-to-brick bond strength at head joints. The overlapping units in running bond masonry will provide more strength across vertical planes because they eliminate the continuous vertical joints that occur in stack bond walls. Crown Repairs The crown or cement cover that rests atop your chimney stack is. The crown should be at least 4'' thick and have a slight outward slope to shed water away from the chimney flue. The purpose of horizontal joint reinforcement in stack bond masonry is to limit vertical cracking. Count on us for quality crown repairs, tuckpointing, chimney rebuilds. Lay the wire mesh half way through the pour so it's in the middle of the concrete.Ĭut the mesh slightly smaller than the crown so it's not exposed to moisture which will lead to rust, possibly causing the crown to crack. Concrete is stronger and can withstand temperature fluctuations and weather exposure better than mortar.įor extra strength, 1''x 1'' wire mesh should be placed in the concrete during the pour. Use concrete for construction not mortar. The crown should extend at least 2'' past the outside wall and contain a drip edge underneath. Proper chimney crown replacement requires a few important steps which will substantially increase the life of the crown.ĭo not make the crown flush with the outside chimney wall. Second, water can run between the crown and the chimney flue causing damage to the clay tile or even worse, causing damage to the chimney damper, smoke chamber, or the fireplace itself. This moisture also causes the bricks to separate and eventually fall apart. ![]()
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