How To Build A Outdoor Fireplace With Cinder Blocks

How To Build an Outdoor Fireplace With Cinder Blocks

An outdoor fireplace can transform a backyard into a cozy and inviting space, perfect for relaxation and entertainment. Constructing a fireplace using cinder blocks offers a cost-effective and relatively simple approach to achieving this. Cinder blocks are durable, readily available, and easy to work with, making them an excellent choice for DIY enthusiasts. This article provides a comprehensive guide on how to build an outdoor fireplace with cinder blocks, outlining the necessary steps and considerations for a successful project.

Before embarking on the construction process, meticulous planning is crucial. This involves determining the desired size and design of the fireplace, obtaining the necessary permits, and preparing the construction site. Accuracy in these initial steps will significantly contribute to a stable and aesthetically pleasing final product.

Planning and Preparation

The first step is to conceptualize the fireplace design. Consider the available space, intended use, and desired aesthetic. Simple rectangular or square designs are easiest to construct with cinder blocks. Sketching out the design on paper, including dimensions, is highly recommended. This visual representation will serve as a blueprint throughout the building process.

Research local building codes and regulations regarding outdoor fireplaces. Many municipalities require permits for such structures, and failure to obtain the necessary approvals can result in fines or the need to dismantle the fireplace. Check for setback requirements from property lines, restrictions on fire size, and any specific materials that are required or prohibited.

Site preparation is a critical step. Choose a level area away from flammable materials like trees, fences, and overhanging structures. Clear the area of grass, vegetation, and debris. A solid foundation is essential for the stability of the fireplace. Ideally, a concrete slab should be poured as a foundation. The slab should extend beyond the footprint of the fireplace by several inches on all sides. Alternatively, a compacted gravel base can be used, although this is less stable than concrete. To create a gravel base, excavate the topsoil to a depth of 6-8 inches, fill with compacted gravel, and ensure it is level.

Gather all necessary materials and tools. The quantity of cinder blocks will depend on the size of the fireplace design. In addition to cinder blocks, you will need mortar mix, sand, gravel (if using a gravel base), fire bricks (for the firebox), fire clay mortar, a trowel, a level, a measuring tape, a wheelbarrow or mixing tub, a shovel, a tamper (for compacting gravel), safety glasses, and work gloves. Having all materials readily available will streamline the construction process.

Construction Process

With the planning and preparation complete, construction can begin. This involves laying the foundation, building the walls, constructing the firebox, and adding finishing touches. Each step requires careful attention to detail to ensure structural integrity and aesthetic appeal.

Begin by mixing the mortar according to the manufacturer's instructions. Add water gradually to the dry mix until a smooth, workable consistency is achieved. Avoid adding too much water, as this can weaken the mortar. A wheelbarrow or mixing tub is ideal for this purpose.

Lay the first course of cinder blocks on the prepared foundation. Apply a generous layer of mortar to the base and the sides of each block before placing it. Use a level to ensure that each block is aligned correctly and the first course is level. This initial course is crucial, as it will serve as the foundation for the rest of the structure.

Continue laying subsequent courses of cinder blocks, staggering the joints for added strength. This technique, known as "running bond," involves offsetting the joints between blocks in each course, ensuring that the seams do not align vertically. Apply mortar to the sides and top of each block before placing it, and use a level to ensure that each course is level and plumb. Periodically check the alignment of the walls with a measuring tape to ensure that they are square.

The firebox is the area where the fire will be contained. This area should be lined with fire bricks, which are designed to withstand high temperatures. Fire bricks are typically smaller and denser than regular bricks or cinder blocks. Build the firebox within the cinder block structure, using fire clay mortar to adhere the fire bricks. Fire clay mortar is specially formulated for high-temperature applications and will not crumble under intense heat. Ensure that the firebox is adequately sized to accommodate the desired fire size.

As the walls are built upward, consider incorporating a chimney or flue to direct smoke away from the seating area. The chimney can be constructed from cinder blocks or other suitable materials, such as clay flue liners. The size and height of the chimney will depend on the overall design and local building codes. Ensure that the chimney is properly supported and securely attached to the main structure.

Allow the mortar to cure for at least 24-48 hours before building a fire in the fireplace. This will allow the mortar to harden and gain strength. After the mortar has cured, slowly burn a small fire to help cure the fire bricks and fire clay mortar. Gradually increase the size of the fire over several days to allow the materials to adjust to the heat.

Safety Considerations and Finishing Touches

Safety should be a top priority during the construction and use of an outdoor fireplace. Adhering to safety guidelines will help prevent accidents and ensure the longevity of the structure.

Always build the fireplace in a location that is away from flammable materials, such as trees, fences, and overhanging structures. Maintain a safe distance between the fireplace and any seating areas. Keep a fire extinguisher or water hose nearby in case of emergencies. Never leave a fire unattended, and ensure that the fire is completely extinguished before leaving the area.

Adding decorative elements can enhance the aesthetic appeal of the fireplace. Options include applying a stucco finish to the cinder block walls, Veneer stones can be adhered to the cinder blocks to mimic the look of natural stone. Painting the cinder blocks with a heat-resistant paint can also improve the appearance. Consider adding a mantel or hearth made from stone, brick, or wood. These features can add a touch of elegance and provide a convenient surface for placing drinks or decorations.

Clean the fireplace regularly to remove ash and debris. Inspect the structure periodically for any signs of damage, such as cracks in the mortar or loose bricks. Repair any damage promptly to prevent further deterioration. Consider applying a sealant to the cinder blocks to protect them from the elements and prevent water damage.

By following these steps, it is possible to construct a functional and visually appealing outdoor fireplace using cinder blocks. The result is a valuable addition to any outdoor living space, providing warmth, ambiance, and a focal point for gatherings with friends and family. The key to a successful project is careful planning, attention to detail, and adherence to safety guidelines.