Fireplaces are a key element of most outdoor room settings, and are usually the focal point of any outdoor living area.
Traditionally, fireplace construction was an art that few masons truly mastered. With the advent of builder-grade metal fireboxes, that masonry art was nearly lost.
Proper design and construction of an outdoor fireplace is particularly challenging, as many of the features that create a functional indoor fireplace do not work well in the outdoor environment, where wind and the elements create drafting problems for shallow fireplaces and for those with tall firebox openings.
Fortunately, modern technology and traditional design experience have combined to create modular masonry fireplace kits, which deliver outstanding performance and simple, straightforward construction requiring a fraction of the time and labor needed to build a fireplace from scratch.
Once the fireplace walls and back are in place, firebrick is installed on the floor and walls of the firebox, to give a neatly finished look and additional insulation for the firebox area.
Building the Fireplace
Construction of the fireplace kit begins with a reinforced concrete pad, of varying depth, depending upon the size of the fireplace and type of finish to be applied to the kit, and specifications for the pad are included in the kit's installation instructions. Adding piers to the pad may be advisable in colder climates, or in areas where soils are unstable. Consult with local building codes or an experienced concrete contractor to determine the requirements for your locality.
These kits are assembled using a multi-purpose ready-mix concrete, formulated to withstand the high operating temperatures found in wood-burning fireplaces. Many models include riser legs, which form a wood storage box below the fireplace. In some cases, a custom base may be desired, and this is simply constructed using concrete block in place of the riser legs.
Stone Age outdoor fireplace kits (and most other outdoor fireplaces) are not designed to be zero-clearance fireplaces, which means the fireplace must be installed with a minimum three inches of clearance between the kit components and any wood framing or other combustible material. If framing is to be in contact with fireplace, the installer may run a course of concrete block between the kit components and the combustible material, to achieve the required clearance.
The chimney sections are being set into place by this crew. In this phase of the project, the crew is installing the lower chimney sections onto the throat of the fireplace.
As the kit pieces are assembled, they should be checked for plumb and level as each layer of kit componentry is added, to ensure a uniform profile that will be easy to finish. Once the fireplace walls and back are in place, firebrick is installed on the floor and walls of the firebox, to give a neatly finished look and additional insulation for the firebox area. Stone Age has also developed refractory panels, which give the same look and performance as traditional firebrick, yet install in minutes and do not require masonry skills.
Once the firebrick or panels are installed, the front lintel of the fireplace is added, as are the throat pieces of the kit. The throat pieces taper to meet the chimney flue, which completes the kit. These kits feature a traditional clay flue tile molded into a high-temperature concrete outer shell, and most kits are approximately eight feet tall when completed. Additional chimney sections can be purchased to increase the overall height of the fireplace kit, which may be required if the fireplace is to be built near a home or other taller structure.
At this point, the fireplace kit is complete, and the installer is now ready to begin the finish application. In many cases, a masonry-compatible finish is applied directly to the fireplace kit, following its outline, however, one of the key advantages of the kit is that it may be used as the core working component of the fireplace, but may be surrounded with concrete block or other non-combustible material, to achieve a unique finished profile.
The application of natural thin stone material to the fireplace kit is achieved using a drystack technique that produces a small grout joint.
Concrete block may be placed directly against the kit components to create any desired shape, and the finish material may be applied to the block, rather than the kit components. Adding block allows adding custom or extended hearths, seating areas around the fireplace kit, or anything the designer can imagine. Wood storage box kits are also available, which create a simple way to add wood storage areas to the side of the fireplace, for a different look.
Once the kit is complete and any reshaping block has been installed, finishing may begin. Any masonry-compatible finish may be applied directly to the kit components, without the need for a preparatory scratch coat of mortar. Stucco is one of the simplest finishes to apply, but may not be popular with the consumer in some areas of the country.
The overall height of the fireplace is approximately 9 feet including the chimney cap, which is tall enough to keep the smoke above the seating area, but will not look overly tall when the planned surrounding elements are in place. From start to finish, a crew of three can complete a fireplace kit installation in about 2 days. If using stucco, this would be shorter, or if using full depth stone veneer that requires a good deal of hand fitting, finishing time would increase.
There is a wide range of high quality man-made stone products available, and these are easily applied to the fireplace kits, although corners may require trimming or special care to get the right look. Thin-cut natural stone is becoming increasingly popular, and many styles have corner pieces available, just like man-made stone products. With thin stone, you may use corners, or may cross-set or tooth the stones together to form a criss-cross pattern at the corners. When applying the stone to angled corners, you may want to cut the stones to an angle that matches the one you will be applying the stone against, or you may consider chamfering the stone, to allow application using a straight line joint at the corner.
The finishing component of the outdoor fireplace is the chimney cap, which should be used on any fireplace, to lessen the amount of moisture reaching the inside of the chimney flue and help prevent birds from nesting in the flue. With the installation of the chimney cap, fireplace construction is complete and the fireplace is ready to be enjoyed by the homeowner.
Modular masonry fireplace kits greatly simplify the construction of fireplaces for outdoor room settings, creating new opportunities for landscape and hardscape installers.