Question: how often should a chimney be cleaned? the fireplace is brick and the chimney is galvanized metal. also, what is the average cost of cleaning? thank you for your response. Answer: Open fireplaces should be looked at every year, or every 4 cords of wood or so....you can simply look at the flue from the bottom or top to see if there is a buildup of soot. The worse type of buildup is the shiny creosote (like a tar), which results when wood is burned without the presence of enough air. Older woodstoves need cleaning at least once a year, even if less than 4 cords are burned...newer woodstoves are cleaner, and the chimney may be quite clean when you check it. Average about $100.00 today.