In the construction of the masonry for any craftsman home fireplace or chimney it is important that the foundation start from solid ground and as far down as the lowest part of the foundation wall of the house itself.
All woodwork must be excluded from inside the chimney and the beams should be framed around the brick work. A fireproof hearth should be constructed with a distance of 12 inches or more from the face of the chimney wherever there is to be an open fireplace.
The best placement for the opening for the fireplace is in the center of the chimney. If a flue passes up on only one side then balance to the chimney can be made by running up studs on the other side to give an equal width without a waste of brick work.
Designing The Flue
It is a safe rule to make the height of the fireplace rather less than the width of the opening and the depth should be at least one-half the height. The average size of fireplaces is made 30 in. wide, 30 in. high, 12 in. deep in the rough brickwork. To this is added the mantel facing giving a depth of about 15 inches.
The smoke flue, in cross section, should be about 1/2 the area of the fireplace opening. That would for the above mentioned size, 30x30, give a cross section of about 75 sq. in. and for this the flue is usually built about 8in. x 8in.
The flue itself should be uniform in size from the throat of fireplace to the extreme top of chimney and sharp turns and unnecessary bends should be avoided.
It is desirable to use terra cotta flue lining as they insure a smooth surface in the flue and also give protection against possibility of a spark going through an open joint of the firebrick work.
The flue linings should be carried a little above the top of the chimney so as to permit a beveled shoulder of cement to run down to meet the brick work. This also leaves a nice clean look to the exterior chimney top.
Make sure that the flue lining is sufficient so that you will have eight inches of brick around the chimney. Around the open fireplaces there should be at least 12 inches of brick work, or 8 inches of brick work with 4 inches of air space, between the fire and any woodwork.
What Is A Chimney Throat?
The space immediately above the fireplace is termed the "throat" and the sides of a chimney throat should run at an angle of about 45 degrees starting at the sides of the fireplace and meeting the flue directly over the center of the fireplace.
The very best option is to build in an iron throat damper. This has the right shape to insure good draft and has the advantage that the damper can be closed when the fireplace is not in use or when the draft of the fire is too strong.
We often see plastering on the inside of a flue as the chimney is being built. It does insure a smooth surface while the work is new, but is not desirable because the plaster will eventually loosen and fall. When it drops out, it pulls some of the mortar from between the bricks and this will make the surface even rougher than it would be if the brick work has not been plastered in the first place.
You must always take precautions to prevent any pulling on mortar between the brick - because loose or missing mortar makes it possible for a spark to pass from the flue to the surrounding woodwork. If you cannot get terra cotta flue linings, have eight inches of the brick work built, but not plastered inside.
Should You Use Wood For A Mantel?
Wood mantels if properly made can be used with entire safety where you have open fireplaces or regular open grates in your Craftsman Style Home.