What is Fireplace?
In this article, I have described all components and procedures required for “How to build a fireplace?”. So, Let’s start.
The fireplace is the interior civil structure of a building or house, where the woods or fuels are safely burned with proper ventilation and escape out of burnt gases through the chimney, so that heat is only regulated inside the room.
Why Fireplace is Made?
The basic purpose of the fireplace is to keep the room warm on cold days and nights. Besides it also increases the aesthetic beauty, decoration, and architectural values and even alters human psychology with a pleasant environment and surroundings.
The fireplace is generally of three types, masonry, prefabricated (zero clearance), and gas type.
Zero clearance fireplace are light weighted firebox enclosure which always remains cool and are placed directly above the hardwood or concrete floors along few inches apart from sidewalls of house.
They are cheap and easier to install in comparison to masonry but are extremely sensible and risky. A great amount of precaution is needed to be adopted.
Gas fireplaces are modern techniques used as an alternative form of the masonry fireplace along with optimization of space, easier installation, environmentally friendly producing less smoke and pollution.
The basic requirement for this is the connection of gas supplies and adequate ventilation.
A masonry fireplace is a vague traditional construction that consists arrangement of different parts steps by steps. They give very efficient heat radiation and also a good appearance to the room or building.
The detail about the masonry fireplace is discussed below in this article as it is a great task for the civil engineers and architects to deal with compare to other types of the fireplace.
How to build a fireplace? – Video (Discription is given below)
Components of Masonry fire place
To design and build the fireplace one must be well informed about its different components and parts. So before explaining how to build a fireplace, I have explained some basic general information about components of the masonry fireplace in sequential order as they are built.
The fireplace basically contains three major components, they are Foundation, Firebox, and Ventilating Units.
The foundation in the fireplace is provided in order to provide structural support as well as in order to insulate the heat, and preventing the transfer of heat to the ground and surrounding area. The foundation includes a footing slab, foundation wall, and structural wall at the top to support the fireplace.
The foundation for the fireplace can be pre-designed along with the design of the building as well as can be later on constructed or design separately.
The foundation wall doesn’t include any voids but sometimes the void along with the pipe fitting leading it to the ash pit is designed so that ashes are not necessary to be clean or withdrawn from the above fireplace inside the room.
2) Fire Box:
The firebox is the major component for burning the fuels or wood and then radiating heat in the room. So, in order words, it is the basic visible part of the fireplace directly when we enter the room. The firebox further contains subunits or parts.
The first part of the firebox is the Base also called hearth support. The base is generally the reinforced slab directly laid on the structural slab or corbel supports or bricks creating an air void between the structural slab and base slab.
The hearth is the base part of the firebox where the fuels are burned. It is generally further divided into the inner hearth and extended hearth.
The inner hearth lies inside the firebox (dome shape) and the extended hearth lies outside the dome as projection in order to prevent the flying sparkle ashes, burnt coals or woods, to get outside the safe zone of the fireplace
4) Fireplace opening
It is the opening void face or area of the firebox that leads to the hearth or chamber where fuels are burnt and gases are exhausted. The fireplace opening is created with help of lintel bands at the top along with the arch shape brick layout at back.
The lintel band is generally reinforced with an angle section of steel allowing the expansion joint as the steel can greatly expand on heating. The band is then concreted or lined with masonry bricks. The heat efficiency of the fireplace depends upon the proper sizing of the openings.
If the opening is small, the fireplace will not radiate enough heat, and if it’s too large, the fuel combustion occurs rapidly leaving large heat. So, the optimum size or dimension should be according to the room size.
5) Combustion chamber
This is the hollow dome-shaped total space surrounded by the hearth and the walls.
The lower portion of the combustion chamber (near the hearth) is vertical to some extent and the above portion is sloped in form of an arch toward the fireplace opening through the arrangement of bricks and mortar to support dampers.
6) Ventilating units:
These include the air passage, throat, damper, smoke shelf, smoke chamber, and chimney. Air passage can be located at bottom of the hearth or at the back vertical section of the firebox for the flow of air and proper burning of fuels.
The Throat is opening directly located at top of the firebox by which gases are exhausted to smoke chamber and then outside of building through the chimney. The cast throats are also available which can be directly placed on top of the firebox.
And moreover, the brick can be layout superficially over such casted throat to give a complete masonry appearance.
The entire throat and the vertical wall form the Smoke chamber. The smoke chamber top is used to form support to the chimney flue.
The back of the smoke chamber is vertical and the sidewalls and the frontal wall (throat) are slopes towards the center. (Just opposite of firebox).
The dampers are doors or valves that close the openings and use to control the burning rate. The dampers can be located in the throat and air inlet.
8) Chimney flue
It is the tubular draft of the fireplace to form the passage for exhaust gases. The size depends upon the opening of the fireplace. The taller chimney has good withdrawing capacity even for the same openings.
How to build fireplace?
The general simple explanation of the manual way to build the masonry fireplace can be explained but the dimension and other factors like aesthetic appearance, building codes, design requirements might slightly alter general procedure.
The general construction procedure of the fireplace includes the location of the fireplace first. The fireplace exhibits a lot of heat and temperature to surrounding thus it must be located in the desired safe room or place.
If the place is needed then treated for a good foundation. Sometimes the stable foundation is preplanned in the design of a building and is constructed during the building construction.
After that, the process is made step by step as the components and parts are explained above sequentially. From the bottom of the hearth to the chimney flue.
The bottom of the hearth is fixed with air passage or ventilation, with help of the tubes. And then are concreted with reinforcement to form the thick base slab. The slab can cross the level of the ground floor if the fireplace is to be located slightly above the ground.
Then the fireplace is lined with refractory bricks and mortars. The materials used must be refractory and fire-resistant as much as possible.
Then the combustion chambers of the firebox are built using normal masonry works as designated shapes and requirements, i.e. the brick of combustion chamber is brought at the slope for forming arch after the certain vertical erection of masonry wall at the back of the chamber.
After that, the lintel bands and angle section are placed to create the frontal opening of the fireplace. The lintel bands include an angle section along with expansion joints. This way the firebox is constructed at the initial stage.
The throat is placed or constructed above the firebox. In the throat, the front face is arched towards the center in order to form the smoke chamber having a vertical wall and spacing at back.
Now then the smoke chambers are covered with a chimney flue. For the construction of chimney flue, the precast hollow blocks are made available which are sequentially arranged one above another to form the tubular channel.
Besides these, the exterior design is further included for the architectural and aesthetic value of the fireplace. These include Mantel, decorative alignment of the hearth extension, fireplace surroundings, backup walls, etc. the air space is cavity wall can also be constructed around the fireplace in order to insulate the heat.
Some basic guidelines for the construction of fireplace
- The footing of the fireplace foundation is generally 300mm thick and extended 150mm extra overall the foundation wall base of the fireplace
- The foundation wall minimum thickness is 200mm.
- The slab above the foundation wall remains below the fireplace and should be thick enough about 300mm to 400mm along with reinforcement.
- The inner hearth is further linked with the refractory noncombustible bricks and mortar joints. It should have a minimum thickness of 100mm.
- The extended hearth should be a minimum of 200mm on each side of the frontal opening and projects till 400mm front from opening (for fireplace opening area less than 0.55m2).
- The fireplace openings are needed to be designed precisely and in an optimum way to maintain efficient heat in the room. However, the general thumb rule can be achieved maintain width and height of opening as suggested by Table 1 and figure 1. (Based on Technical note 19 – Design of fireplace and may alter to different building codes and manuals)
- The dimension of the fireplace can be selected on basis of room size as suggested from Table 2.
- Support above fireplace for lintel bands also depends upon the size of the opening. So it is also adopted on basis of table 1.
- Steel angle must be provided with necessary joint space.
- Refractory bricks and mortar must be used throughout the inner lining of the fireplace.
- A combustion chamber is needed to be constructed with a minimum thickness of 100mm brick wall. The mortar joints should not be more than 6.4mm.
- 25mm air chamber is provided in between backup wall and chambers.
- Throat should be located (min) 200mm above the high point of the frontal fireplace opening.
- The general throat dimension can also be obtained according to the size of the firebox as suggested from Table 1 and Figure 1.
- A high formed damper is recommended to use in the throat.
- A chimney top damper can be used as an alternative to dampers installed at top of the throat.
- The chimney flue dimension depends upon the dimension of the firebox. For this, the standard graph formed by Technical note 19 can be taken
- If the Mantel(combustible) and decorative of the fireplace is to be placed then they should be kept at 6inch far away from fireplace openings.
- If the side mantel is projected more than 38mm then it must have extra clearance projecting beyond 38mm.
- Mantel above the fireplace projecting more than 38mm must not be placed less than 305mm on top of the fireplace opening.
- Air circulating systems that are made to withdraw cooler air of the room and warm it and send back to the room can be achieved help of low voltage fan and pipe arrangements.
I hope this article on “How to build a fireplace?” remains helpful for you.
Happy Learning – Civil Concept
Civil Engineer – Rajan Shresth