How To Build Cinder Block Outdoor Fireplace

How to Build a Cinder Block Outdoor Fireplace

Building a cinder block outdoor fireplace can enhance any backyard, providing a focal point for gatherings and warmth on cool evenings. This project requires careful planning and execution, but with the right tools and instructions, it can be a rewarding DIY endeavor. This article provides a step-by-step guide to constructing a basic cinder block fireplace.

Planning and Preparation

Before beginning construction, check local building codes and obtain any necessary permits. Choose a suitable location for the fireplace, ensuring it's a safe distance from any flammable materials like trees or overhanging structures. Level the ground and prepare a concrete footing that extends beyond the fireplace's dimensions on all sides. The footing's size and depth will depend on the fireplace's size and local frost line regulations. Consult a structural engineer if needed.

Gathering Materials and Tools

Assemble all necessary materials before starting. This includes cinder blocks, mortar mix, sand, gravel, rebar, firebricks, a metal chimney flue, cap, and flashing. Required tools include a trowel, level, measuring tape, safety glasses, gloves, a wheelbarrow, and a mortar mixer (optional but recommended for larger projects).

Laying the Foundation and First Course

Once the concrete footing has cured, begin laying the first course of cinder blocks. Dry-fit the first course without mortar to ensure proper alignment and placement. Then, mix the mortar according to the manufacturer's instructions. Apply a layer of mortar to the footing and carefully place the first cinder block. Check for levelness and plumbness. Continue laying the first course, ensuring consistent mortar joints and proper alignment.

Building the Walls

Subsequent courses are laid in a similar fashion, staggering the joints to provide structural integrity. Insert rebar vertically into the hollow cores of the blocks at specified intervals to reinforce the structure. Consult local building codes for rebar placement guidelines. Fill the cores with concrete after placing the rebar.

Constructing the Firebox

Once the walls reach the desired height for the firebox opening, begin lining the inside with firebricks. Firebricks can withstand high temperatures and protect the cinder blocks from damage. Use a heat-resistant mortar specifically designed for firebricks. Ensure proper spacing and alignment of the firebricks.

Installing the Chimney Flue

The chimney flue is crucial for proper ventilation and smoke removal. Install the metal flue according to the manufacturer's instructions. Ensure the flue extends above the fireplace opening and meets local building code requirements for height. Secure the flue to the cinder block structure using appropriate fasteners and flashing to prevent water penetration.

Adding the Finishing Touches

Once the mortar has dried completely, add any desired finishing touches, such as a cap for the chimney and a hearth extension. Consider applying a sealant to the exterior cinder blocks to protect them from the elements and enhance their appearance. Allow ample curing time for all materials before using the fireplace.

Safety Precautions

Always prioritize safety when working with construction materials and fire. Wear appropriate safety gear, including eye protection and gloves. Follow all manufacturer instructions for materials and tools. Consult with professionals if you have any doubts or concerns about any aspect of the construction process. Ensure adequate ventilation around the fireplace and never leave a fire unattended.