A chimney is a structure which protrudes through your roof and provides ventilation for hot gases or smoke from a stove, boiler, furnace or fireplace. Chimneys were originally build using bricks and mortar. Today in newly build homes, wood burning fireplaces are very uncommon. Most commonly today central heating is used with non-structural gas vent pipes which allow chimneys to be built from wooden structures. On a sloped roof where a chimney penetrates through the roof, flashing is used for water proofing. You will have base flashing installed around the bottom of chimney which overlaps with the roofing material. On a wooden structure chimney the siding will overlap the base flashing for a water proof seal. On a concrete structure chimney you will have additional flashing installed called counter flashing. This is installed by cutting into the concrete joints, pining the flashing into the cut and then installing mortar into the remaining gaps between the flashing and cut.
Chimney pots and caps are very important for a few reasons. A chimney pot placed on top will inexpensively expand the length of the chimney and improve the chimney’s draft. A chimney cap with wire mesh will minimize burning debris from rising out of the chimney and making it onto the roof and also prevent birds, squirrels and other rodents from nesting in the chimney. The other benefit to a chimney cap is preventing rain or snow from going down the chimney.