Chimney Crown Installations
The Purpose of a Cement Crown & Rain Cover
Chimney #1 – has no cement crown or mortar wash/splay on top. The rain hits the top of the bricks and soaks in, causing wet walls inside your chimney. The normal expansion, contraction and freeze cycles cause the mortar to loosen and pop out from between the bricks. This can sometimes be repaired by tuck-pointing, but usually should be totally re-built. Also with no crown, water can seep between the flue tiles and bricks and will run down inside the chimney and deteriorate the firebox, which results in costly repairs to the damper, firebricks, ceilings, etc.
Chimney #2- has a mortar wash/splay at the top, which prevents water from seeping in through the top of the chimney (for a while). However, the water still runs down the sides of the bricks, makes them wet and eventually the faces of the bricks pop off (spalling), which can only be repaired by rebuilding the chimney. Without an expansion joint around the tile, the thermal shock (heat) usually cracks the mortar wash/splay during the first season use.
Chimney #3 – has a cement crown with expansion joints. The reason for expansion joints is to prevent the damage caused by constant freezing and thawing. The cement is angled slightly down, overhangs the bricks by at least 2” and the water runs off the crown down to the roof, never touching the sides of the bricks.
The proper way is outlined in Chimney #3.
Finish off the top of your chimney like this and it will give your chimney many extra years of life. We also suggest that a rain cover with screening be installed over the flue tile to prevent rain from pouring directly into the firebox – and to keep animals and birds out. Our rain covers are 100% stainless steel and are guaranteed for life.