Masonry fireplaces, whether wood-burning or gas, are cozy elements that represent the epitome of home for many owners. Yet cracks in a brick or other type of masonry chimney are the first warning sign that your chimney is on the road to ruin. Small cracks in the summer can surprisingly become large cracks by next spring. Letting those larger cracks remain deepens the penetrating effect of rain, snow, and ice, further coring into the brick. Then the water begins to work its way down, sometimes between the outer brick and the flashing, sometimes farther inside, between the outer brick and the flue.
Left unchecked, all of this spells disaster for roof systems and interior ceilings, insulation, wall studs, and even floors. Worse, cracks that continue from the flue to the exterior are one cause behind a terrifying, devastating phenomenon called a chimney fire.
Mortar holds bricks together. New mortar is smooth and solid. But as the seasons go by, the elements batter the mortar, causing it to crumble. Since mortar is softer than brick, the mortar will always deteriorate first.
One major avenue for water to enter your home and cause damage is between the flues and the crown. Typically, a gap will form in this area after a number of seasons. Water that enters this gap can move all of the ways down the flue.
With the wire brush, clean out any debris such as moss and mortar. Load up the caulking gun with high heat mortar, snip the end of the nozzle, and pierce the interior seal. Squeeze enough caulk to fill but not exceed the area of the gap.
Finally, Individual chimney bricks that have a small crack or two can be repaired with a high-heat mortar and a caulking gun.