Is it a good idea to remove ashes from the fireplace or wood stove every time you build a fire?
People who burn wood know that the consistent by-product of having a wood fire is ash.  While the volume is going to be determined by the actual species of wood; softwoods weigh less and will have the potential to generate more ash.  In any case there will always be ash remaining in the combustion chamber after the wood fuel is burned.

There are many ways this ash can be put to good use. Did you know that it is not a good idea to remove the ash from the fireplace or wood stove every time you build a fire? Having a 1-inch layer of ash on the floor of the firebox during the regular heating season will make it easier to build and maintain a fire.  The hot coals tend to nestle into the ash and glow, adding more heat to the fuel and reflecting the heat back into the fire. 

Handling Ash Information

Of course, this, like almost everything else, should only be done in moderation.  For example; if the ash in your fireplace is so deep that it is coming in contact with the bottom of your grate, it can cause the grate to burn out prematurely.  It is the same concept mentioned earlier; the heat is reflected back to the fire, the grate just happens to be in the way and will suffer over time.  Additionally, if you have a wood stove with a large amount of ash it will reduce the volume of fuel that can be added to the firebox.

However, many long, narrow stoves that burn from the front to the back will benefit from the removal of the ash just inside the door.  That ash is completely spent.  You can then move the hot coals from the rear of the stove into the cavity you have created and the fresh fuel will ignite quickly and easily when the incoming combustion air rushes across them.  In either case, if the ashes are cleaned out, you will find that it is often more difficult to build a fire because you must heat up all of the brick in the firebox to saturation before the fire can really take off.

This also leads us to another benefit of that small layer of ash; it protects the floor of the firebox.  Usually the dirtiest part of the burn is the beginning stages of the fire.  This can be addressed with the top down burn method.  Getting the fire blazing as quickly as possible will reduce the amount of unspent fuel that can cling to the interior of the flue or exit the chimney.

At the end of the heating season, it is appropriate to remove the ashes from your fireplace and stove.  The ashes actually have the potential to draw moisture that can cause deterioration of metal components.  The alkaline nature of the ash combined with moisture can be very destructive to both the masonry and metal components whether you are using a masonry fireplace, factory-built fireplace or a wood stove. 

Taken from CSIA website.