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Combustion Air Valve or Distribution Box
The valves inside the house for the combustion air tubes can be regular full flow gate valves when using standard size galvanized pipe.
Caution: Do not use globe valves because they greatly restrict the air flow.
Intake pipes
or tubes should be insulated from the outside house wall up to the valve inside the house to reduce heat exchange between inside and the outside. Where 3 x 3 inch downspouting or other type tubes are used the builderlcrafter will have to design an insulated guillotine or insert valve substitute. Provisions should be made for partial valve closure, as opposed to only fully opened or fully closed positions. Use of a valve distribution box will enable one valve to control the air flow as opposed to a valve for each tube.
VALVE f DISTRIBUTION BOX VALVE DISTRIBUTION r OUTSIDE WALL II
AIR FLOW TO MASONRY STOVE
;ID€ WALL
COMBUSTION
AIR INTAKE 7 COMBUSTION
AIR INTAKE
FOUNDATION HAL
TOP VIEW SIDE VIEW
Insect screen (118 x 118 inch hardware cloth) should be installed over the outside openings to avoid entry by rodents, insects, animals or trash. Btiy enough wire for the insect screen and screening of the sand for the ornamental brick mortar mix. The screen on the air duct should be removable to aid in duct clean-out if something accidentally falls into the air tube. The surface area of the wire screen should be twice the area of the tube. Avoid water entry into the air tubes by down turns or by reverse angle cuts.
r OUTSIDE WALL
OUTSIDE WALL
AIR INTAKE
1 INSECT SCREEN FOUNDATION WALL COVER
AIR INTAKE
- INSECT SCREEN
FOUNDATION WALL
Brick and Mortar Suggestions Brick and mortar should be selected both for ornamental value and resistance to high temperature. Use fireplace quality (or better) 4% x 9 x 2% inch firebrick and high temperature firebrick mortar for the firebox. This quality brick must be carried throughout the firebox structure, including the oven and first flue run. After the first flue run, standard face brick or common brick and sand mortar has been used with no apparent problems. Standard brick and sand mortar is lower in cost than firebrick and firebrick mortar but will add some difficulty to construction details. For this reason our drawings are based on firebrick throughout the firebox, the oven, the flue runs and into the first few inner (filler) bricks of the chimney. Caution: consult your supplier on details for handling the mortar and avoiding air bubbles between bricks or possible freezing when using air setting high temperature mortar. Firebrick mortar is normally applied as a very thin coat with a paintbrush and each brick slides (scrubs) into place to eliminate air bubbles.
36,00 ,/8" FLUE TiLE I
For the exterior (safety) ornamental wall, any type brick or stone will be satisfactory. Only a very limited area of this exterior wall will rise above 140 degrees Fahrenheit (the area near the primary flue exit at the rear of the firebox may be hotter). Select masonry materials which can withstand the temperature without cracking. Since the outside wall will be viewed by the home owner, your own imagination and preference will be a primary factor in choosing materials. These exterior walls have been constructed of ornamental stone, common brick, adobe, face brick, concrete with ceramic tile, or any combination of materials.
Regardless of the base materials selected, the mortar should be mixed from clean sand screened through an 8 x 8 inch mesh screen. Do not use sand screened through 1/16 of an inch or smaller mesh. Do not use more than ten (10) percent lime
in the mortar and avoid Missouri river sand because it usually contains carbon impurities from coal. Ten (10) percent by volume, of fly ash in addition to ten (10) percent lime added to the cement sand mortar will help to make a smoother easier to handle mortar.
A bag of cement weighs 94 pounds, ten (10) percent by volume of fly ash is about 10 pounds per bag. Anti-mortar setting materials are available at some concrete ready-mix plants to retard mortar set up, this slows the setting of the mortar (check with the supplier). Anti-setting material is not necessary with lime added to mortar. For the small quantity of mortar required, it may be best to use a
pre-dried, pre-mixed mortar from a hardware store or lumber yard. Permanent colors can be added to the mortar at the time of mixing. Uniformity in mixing of materials is very important even for non-colored mortar.
Avoid over-wetting the mortar because it will cause excessive cracking and shrinking. If the sand in the mortar is too fine or the mortar is too rich from cement the mortar will compress from brick weight. This will limit the height
of the wall that can be laid in a given time period.
OPPOSING WEDGES
Specialized Bricks:
Arch bricks are manufactured in several specific sizes. Consult your supplier on the exact number of each size and ask about the proper skew brick to be used to start the arch that spans the horizontal distance across the arch. It is best to lay out the bricks on the floor, draw a pattern and form a fiber board or plywood arch form, to support the arch during construction. The arch form should be precisely cross-leveled when it is set in the fireplace, by the use of opposing wooden wedges. The wedges aid in removal of the form after the mortar has dried.
Always allow adequate drying time (24 to 48 hours) before removing the arch form and avoid cracking the arch. In addition to arch brick, certain other specific size firebricks are available by special order. These often are handy in some places for filling spaces and spanning openings. They are more expense than standard bricks
but are usually worth the price when you consider broken bricks from attempts at cutting without ceramic saw blades. Cutting of bricks, even with proper equipment, is time consuming. Any saw blade used to cut brick should state its exact use in the label. Note that brick dust is destructive to the armature of portable circular saws.
Combustion Air Valve or Distribution Box
The valves inside the house for the combustion air tubes can be regular full flow gate valves when using standard size galvanized pipe.
Caution: Do not use globe valves because they greatly restrict the air flow.
Intake pipes
or tubes should be insulated from the outside house wall up to the valve inside the house to reduce heat exchange between inside and the outside. Where 3 x 3 inch downspouting or other type tubes are used the builderlcrafter will have to design an insulated guillotine or insert valve substitute. Provisions should be made for partial valve closure, as opposed to only fully opened or fully closed positions. Use of a valve distribution box will enable one valve to control the air flow as opposed to a valve for each tube.
VALVE f DISTRIBUTION BOX VALVE DISTRIBUTION r OUTSIDE WALL II
AIR FLOW TO MASONRY STOVE
;ID€ WALL
COMBUSTION
AIR INTAKE 7 COMBUSTION
AIR INTAKE
FOUNDATION HAL
TOP VIEW SIDE VIEW
Insect screen (118 x 118 inch hardware cloth) should be installed over the outside openings to avoid entry by rodents, insects, animals or trash. Btiy enough wire for the insect screen and screening of the sand for the ornamental brick mortar mix. The screen on the air duct should be removable to aid in duct clean-out if something accidentally falls into the air tube. The surface area of the wire screen should be twice the area of the tube. Avoid water entry into the air tubes by down turns or by reverse angle cuts.
r OUTSIDE WALL
OUTSIDE WALL
AIR INTAKE
1 INSECT SCREEN FOUNDATION WALL COVER
AIR INTAKE
- INSECT SCREEN
FOUNDATION WALL
Brick and Mortar Suggestions Brick and mortar should be selected both for ornamental value and resistance to high temperature. Use fireplace quality (or better) 4% x 9 x 2% inch firebrick and high temperature firebrick mortar for the firebox. This quality brick must be carried throughout the firebox structure, including the oven and first flue run. After the first flue run, standard face brick or common brick and sand mortar has been used with no apparent problems. Standard brick and sand mortar is lower in cost than firebrick and firebrick mortar but will add some difficulty to construction details. For this reason our drawings are based on firebrick throughout the firebox, the oven, the flue runs and into the first few inner (filler) bricks of the chimney. Caution: consult your supplier on details for handling the mortar and avoiding air bubbles between bricks or possible freezing when using air setting high temperature mortar. Firebrick mortar is normally applied as a very thin coat with a paintbrush and each brick slides (scrubs) into place to eliminate air bubbles.
36,00 ,/8" FLUE TiLE I
For the exterior (safety) ornamental wall, any type brick or stone will be satisfactory. Only a very limited area of this exterior wall will rise above 140 degrees Fahrenheit (the area near the primary flue exit at the rear of the firebox may be hotter). Select masonry materials which can withstand the temperature without cracking. Since the outside wall will be viewed by the home owner, your own imagination and preference will be a primary factor in choosing materials. These exterior walls have been constructed of ornamental stone, common brick, adobe, face brick, concrete with ceramic tile, or any combination of materials.
Regardless of the base materials selected, the mortar should be mixed from clean sand screened through an 8 x 8 inch mesh screen. Do not use sand screened through 1/16 of an inch or smaller mesh. Do not use more than ten (10) percent lime
in the mortar and avoid Missouri river sand because it usually contains carbon impurities from coal. Ten (10) percent by volume, of fly ash in addition to ten (10) percent lime added to the cement sand mortar will help to make a smoother easier to handle mortar.
A bag of cement weighs 94 pounds, ten (10) percent by volume of fly ash is about 10 pounds per bag. Anti-mortar setting materials are available at some concrete ready-mix plants to retard mortar set up, this slows the setting of the mortar (check with the supplier). Anti-setting material is not necessary with lime added to mortar. For the small quantity of mortar required, it may be best to use a
pre-dried, pre-mixed mortar from a hardware store or lumber yard. Permanent colors can be added to the mortar at the time of mixing. Uniformity in mixing of materials is very important even for non-colored mortar.
Avoid over-wetting the mortar because it will cause excessive cracking and shrinking. If the sand in the mortar is too fine or the mortar is too rich from cement the mortar will compress from brick weight. This will limit the height
of the wall that can be laid in a given time period.
OPPOSING WEDGES
Specialized Bricks:
Arch bricks are manufactured in several specific sizes. Consult your supplier on the exact number of each size and ask about the proper skew brick to be used to start the arch that spans the horizontal distance across the arch. It is best to lay out the bricks on the floor, draw a pattern and form a fiber board or plywood arch form, to support the arch during construction. The arch form should be precisely cross-leveled when it is set in the fireplace, by the use of opposing wooden wedges. The wedges aid in removal of the form after the mortar has dried.
Always allow adequate drying time (24 to 48 hours) before removing the arch form and avoid cracking the arch. In addition to arch brick, certain other specific size firebricks are available by special order. These often are handy in some places for filling spaces and spanning openings. They are more expense than standard bricks
but are usually worth the price when you consider broken bricks from attempts at cutting without ceramic saw blades. Cutting of bricks, even with proper equipment, is time consuming. Any saw blade used to cut brick should state its exact use in the label. Note that brick dust is destructive to the armature of portable circular saws.
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