Chimneys

When they dont work, they fill the room full of smoke and make life unbearable for the occupants or dont draw properly enough to heat the room.
When they do work you dont notice that they are working properly.

Hopefully we can dispense with some of the myths here about why chimneys work or dont work.

I had the great fortune of living in Ballarat Australia for over 20 years where the winters are cold, so I had many opportunities to build fireplaces and chimneys, all of them worked.

Causes for chimneys to smoke.

•The top of the roll back on the fire box is situated far too low in relation to the front lintel or arch that forms the fire box front or chimney breast.
Remedy: Increase the height of the roll back so it is at least 100mm above the front lintel or arch that forms the fire box front or chimney breast.

•The flue is far too low in height in relationship to the roof, it must be at least 300mm above the roof ridge line, being too low will cause a down draught.
Remedy: Increase the height of the flue by adding more courses.

•There are trees or other obstacles that block the flow of air around the top of the flue which causes a down draft.
Remedy: Increase the height of the flue by adding more courses, or remove the obstruction.

•The flue is obstructed or blocked.
Remedy: Clear the blockage from the flue, it may be soot, or loose or fallen bricks.

•The flue isnt formed properly, the flue must be a continuous size, or a gradual taper all the way.
Remedy: The flue must be properly formed and gathered when constructed, if the flue goes from fire box size (720 x 480mm, as an example) to flue size (240 x 240mm) in the matter of a few courses the smoke will billow out the front of the fireplace as it will take the path of least resistance.

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Old Fire Place

Old Stove

Old Fire Place1

Typical Old Flue Arrangement

Chimney