How To Build A Fieldstone Outdoor Fireplace

An outdoor fireplace offers a captivating focal point for any backyard, providing warmth, ambiance, and a natural gathering space for relaxation and entertainment. Building a fieldstone outdoor fireplace is a challenging yet rewarding project for experienced DIY enthusiasts or those with a basic understanding of masonry. This article details the process, outlining the necessary steps and considerations for constructing a safe, functional, and aesthetically pleasing fieldstone fireplace.

The success of this project hinges on meticulous planning, proper material acquisition, and adherence to sound construction techniques. While fieldstone offers a rustic and natural aesthetic, its inherent irregularity requires careful selection and placement to ensure structural integrity and visual harmony. It is strongly recommended to consult local building codes and regulations before commencing any construction. Permits may be required, and adherence to safety standards is paramount.

Planning and Preparation

Before any physical work begins, a comprehensive plan must be developed. This plan should encompass the fireplace's dimensions, style, location, and material requirements. The location is crucial; consider proximity to the house, prevailing winds, nearby trees, and property lines. Ensure adequate clearance from combustible materials, such as fences, decks, and overhanging branches. A minimum clearance of 10 feet is generally recommended, but local codes may specify a greater distance.

Determining the size and style of the fireplace is the next step. While personal preference plays a significant role, the fireplace should be proportional to the surrounding landscape. A small fireplace can appear insignificant in a large yard, while an oversized fireplace can overwhelm a smaller space. Consider the overall architectural style of the house and strive for a design that complements it.

Material estimation is essential for cost control and project efficiency. Fieldstone is typically sold by weight or volume, and the amount required will depend on the fireplace's dimensions and the size of the stones used. In addition to fieldstone, you will need concrete blocks (CMUs) for the fireplace's core, firebricks for the firebox lining, mortar, concrete mix for the foundation, and possibly rebar for reinforcement. A detailed materials list will help prevent unnecessary trips to the hardware store and ensure you have everything needed to complete the project.

Tools and equipment are also critical. Essential tools include a shovel, wheelbarrow, level, trowel, mortar mixer (optional but highly recommended), brick hammer, chisel, safety glasses, work gloves, and a measuring tape. For cutting stones, a masonry saw or angle grinder with a diamond blade is necessary. Proper safety gear, including eye protection, gloves, and a dust mask, should be worn at all times during the construction process.

Constructing the Foundation and Core

The foundation is the critical base that supports the entire fireplace structure. A properly constructed foundation is essential for preventing settling, cracking, and eventual collapse. The foundation should extend below the frost line to prevent damage from freezing and thawing cycles. Contact your local building department to determine the frost line depth in your area.

Begin by excavating the area for the foundation. The excavation should be larger than the planned footprint of the fireplace to allow for proper footing. The depth of the excavation will depend on the frost line depth and the desired height of the finished fireplace. Once the excavation is complete, compact the soil at the bottom with a hand tamper. This will provide a stable base for the concrete pour.

Construct a form for the foundation using plywood or dimensional lumber. The form should be square and level, and the inner dimensions should match the desired footprint of the fireplace. Reinforce the form with stakes to prevent it from bowing or shifting during the concrete pour. It is advisable to use rebar within the foundation to add strength and prevent cracking. Place the rebar in a grid pattern, ensuring it is adequately embedded within the concrete.

Mix the concrete according to the manufacturer's instructions. Pour the concrete into the form, filling it to the desired level. Use a shovel or rake to distribute the concrete evenly and eliminate air pockets. Use a concrete vibrator (if available) to further consolidate the concrete and ensure a dense, strong pour. Once the concrete has been poured, use a screed board to level the surface. Allow the concrete to cure for at least 7 days before proceeding with the next step. Keep the concrete moist during the curing process to prevent cracking.

After the foundation has cured, begin constructing the core of the fireplace using concrete blocks (CMUs). The core provides the structural support for the fieldstone veneer. Lay the first course of blocks on a bed of mortar, ensuring they are level and plumb. Use a level to check the alignment of each block and make adjustments as needed. Stagger the joints between the blocks to increase the structural integrity of the wall.

Continue laying courses of blocks, using mortar to bond them together. Pay close attention to the dimensions of the firebox opening, as this will affect the design of the firebox. As you build the core, consider incorporating features such as a smoke shelf, which helps to prevent downdrafts, and a damper, which controls the airflow through the chimney. These features require careful planning and execution.

Installing the Firebox and Chimney

The firebox is the interior chamber where the fire is built. It must be constructed from fire-resistant materials, such as firebricks, to withstand the high temperatures generated by the fire. Firebricks are specifically designed to withstand thermal shock and prevent cracking or spalling.

Lay the firebricks using a refractory mortar, which is formulated to withstand high temperatures. Begin by laying the firebricks for the floor of the firebox, ensuring they are level and tightly fitted together. Then, proceed with the firebrick walls, using a staggered pattern to create a strong and durable structure. Ensure the firebox is properly sized to accommodate the desired size of the fire. Consider the height and width of the opening, as well as the depth of the firebox.

The chimney is responsible for drawing smoke and combustion gases away from the firebox. The chimney should be properly sized to ensure adequate draft and prevent smoke from billowing back into the yard. The height of the chimney also affects the draft. A taller chimney generally provides a stronger draft.

The chimney can be constructed from CMUs or a pre-fabricated chimney liner. A pre-fabricated chimney liner offers several advantages, including ease of installation and improved safety. Chimney liners are typically made from stainless steel or other durable materials and are designed to withstand high temperatures and corrosive gases. Mortar the chimney blocks together, making sure to use a chimney mortar formulated for the temperatures that will be reached through consistent use. A smoke shelf and smoke chamber must be included to insure proper drafting and reduce the amount of backdraft from occurring.

Ensure the chimney extends at least 2 feet above the highest point of the house or any nearby obstruction. This will help to prevent downdrafts and ensure proper ventilation. Install a chimney cap to prevent rain, snow, and debris from entering the chimney.

Applying the Fieldstone Veneer

The fieldstone veneer is the decorative exterior layer of the fireplace. It provides the aesthetic appeal and creates the desired rustic look. Selecting the right fieldstone is crucial. Choose stones that are consistent in color and texture, and that vary in size and shape to create a visually interesting appearance.

Before applying the fieldstone, prepare the surface of the CMU core. Scratch the surface with a chisel or wire brush to create a rough texture that will improve the adhesion of the mortar. Also, clean the stones with a brush to remove dirt and debris. Pre-wetting the stones can also help improve adhesion in dry environments. Mix the mortar according to the manufacturer's instructions. The mortar should be the consistency of peanut butter – not too wet and not too dry.

Begin applying the fieldstone veneer from the bottom up. Start with larger stones at the base of the fireplace and use smaller stones towards the top. Apply a generous amount of mortar to the back of each stone and press it firmly onto the CMU core. Use a level to ensure the stones are properly aligned and plumb. Fill the joints between the stones with mortar, using a trowel to smooth the surface. Vary the size and shape of the stones to create a natural-looking appearance.

As you apply the fieldstone, pay attention to the overall pattern and composition. Strive for a balanced and harmonious look. Avoid placing stones in a repetitive pattern. Clean excess mortar from the surface of the stones with a damp sponge. This will prevent the mortar from staining the stones. Allow the mortar to cure for at least 24 hours before applying any sealant or finishing touches.

The construction of a fieldstone outdoor fireplace constitutes a significant undertaking requiring meticulous planning, proficient execution, and adherence to safety protocols. Success hinges on careful material selection, sound construction techniques, and a thorough understanding of masonry principles. While this guide provides a comprehensive overview of the process, consulting with experienced masonry professionals is highly recommended, particularly for those with limited experience in similar projects.