How to Build Wood Burning Fireplaces

In spite of the fact that there are much more efficient ways to heat a home, we still enjoy the age-old pleasure of sitting around a fire in the evening. So what should we know before we commit ourselves to building a wood burning fireplace? There are some necessary features which, if missing, will cause your fireplace to increase your heating bills rather than reduce them. There are many types, designs, and sizes, so these instructions can only be general in nature. Work out the details for your specific fireplace and put them in the blueprints.

Difficulty:

Challenging

Instructions

Things You'll Need

• Building permit
• plans/blueprints
• enough material to complete fireplace
• cement tools
• carpentry tools
• time and money

1. First, check with your local Building Department. You will need a building permit unless you live beyond the reach of any government, and there's little chance of that being the case. They will answer many of your questions for you while explaining what they require you to do. You will definitely be required to supply them with complete plans of your fireplace construction. You will probably be required to hire an architect or an engineer to approve your plans.

2. Ash clean-out

   As you are preparing your blueprints of the fireplace, keep these thoughts in mind. There are mathematical relationships between the sizes of the room to be heated, the firebox, the damper, and the flue. Get these specific measurements from an architect. The height of the chimney must be 2 feet above the peak of the house, or 3 feet above a flat roof. You will save yourself a lot of trouble if you plan a compartment in the wall near the fireplace through which you bring in the wood supply. This must be locked from the inside. An ash disposal compartment below the firebox with a clean-out door is needed. If the fireplace is on an outside wall of the house, the clean-out can be right outside in the back of the fireplace. If the fireplace is located on an interior wall, the clean-out must be in a basement area. As one question leads to another, now you'll want a basement door so you don't have to carry the ashes up through the house to get them out! Air intake for the fire must come from the outside, or your fire will suck warm air out of the house and up the chimney. When planning an air intake for the fire, you'll want glass doors to keep the cold outside air only in the fireplace, not all through the house. On the outside of this air intake you need a removable steel screen and vent cover or you will have small unwanted guests dropping in for meals.

3. The foundation must support the fireplace and chimney. Plan to have it extend at least 6 inches beyond the perimeter of the fireplace. The foundation should be of concrete at least a foot thick reinforced with steel wire or rebar. It can be advantageous if this is part of the house foundation. A separate foundation could settle, causing cracks in your finished wall. Be sure the foundation is level, and if you are building in winter, don't let the concrete freeze.

4. Prefabricated firebox

   Next you must build up from the foundation with cement blocks to the floor level where you want the hearth and firebox. This block construction will enclose the ash compartment and air intake system if you put them in the design. The firebox may be prefabricated of steel or brick material. These systems are built to the correct specifications with the damper already inside. All you have to do is add the chimney and finish the front. If you build the firebox yourself, you will need those size specifications from an architect. Using fire brick for the wall of the firebox will require fireclay to bond the fire brick together. Cement breaks down and cracks in the heat and gases of the fire. The damper must be as wide as the opening of the firebox. If you are "doing it yourself" instead of using a prefabricated unit, you must build the support structure of the fireplace and chimney at this time.

5. Inside design

   Above the throat and damper you must make the smoke shelf. This helps create proper draft in the chimney. Your chimney may be of clay liners or steel pipe depending upon what kind of firebox you choose.

6. Chimney and flue lining

   Allow 4 inches between the lining and the exterior chimney material. When building through the roof, allow 2 inches clearance around the chimney. This allows for expansion with extreme temperature changes.

7. Flashing

   Metal flashing is set into the joints of the chimney exterior and bent over the roof surface. If the location of the chimney requires it, a saddle must be built on the roof on the upper side of the chimney to deflect rain runoff.

8. Cap and spark arrester

   Use concrete to make the top of the chimney. Slope the chimney top to drain water. The lining should extend a few inches above the concrete. Again, if you are working in winter, keep the cement warm for at least 2 days. Attach a metal cap and spark arrester to the top of the chimney lining.

9. Air vents & doors

   When you build the front of the fireplace, incorporate air vents that allow air to circulate behind the fire wall. You need a steel lintel to hold up the rock above the firebox opening unless you create a stone arch. The glass doors get put in too. Once you've cleaned up, you can now settle into a chair and enjoy that evening by the fire.

Tips & Warnings

• Cooperate with construction crews, the Building Inspector and the Building Department. Any construction can become difficult when crews are at odds with each other.