How to Build a Fire Pit

Building a fire pit is one of the more satisfying and achievable weekend patio projects for a homeowner with basic DIY skills. No specialist trades are required for a standard block-constructed fire pit, the materials are available from any home improvement store, and the result is a permanent, attractive feature that adds genuine outdoor living value to the space. This guide covers two build approaches: a simple unmortared block ring suitable for most residential patios, and a mortared construction for a more durable and finished result.

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Before any excavation begins, check with your municipality about fire pit regulations, setback requirements from structures and property lines, and any permit requirements. Many jurisdictions require a minimum clearance of 10 feet from combustible structures, and some require a permit for permanent installations. Starting with this check saves a lot of remedial work later.

Before You Build

Site Selection

Site selection determines safety, usability, and durability. The fire pit should be placed at least 10 feet from any structure, this includes the house, fencing, sheds, pergolas, and overhead tree branches. Prevailing wind direction matters: a fire pit placed where wind consistently blows smoke toward the house or a neighboring property will cause ongoing problems regardless of how well it is built.

A low-lying area where water pools after rain is a poor location. Ground moisture beneath the fire pit accelerates material degradation and creates a wet fire bed that is difficult to light and produces excessive smoke. A slight grade that sheds water away from the pit is ideal.

Choosing a Location on the Patio

If the fire pit is going on an existing patio surface, the surface material determines what additional preparation is needed. Pea gravel is the most naturally compatible surface for a DIY fire pit, it is already fire-safe, provides drainage, and requires no protective layer between the fire pit and the surface. The pea gravel patio pros and cons guide explains the full compatibility picture including fire feature use.

Concrete pavers and natural flagstone are also compatible with a block-built fire pit but should have a sand or gravel base layer under the block ring to prevent the thermal cycling of the fire from cracking the patio surface beneath. Composite decking is not a suitable surface for a permanent built fire pit. For guidance on what goes under a fire pit on different surface types, see the best surface to put under a fire pit guide.

What Size to Build

A fire pit inner diameter of 36 to 44 inches is the most practical range for a standard residential patio. This size accommodates split firewood logs of standard length (16 to 18 inches) without requiring them to be cut down, produces sufficient heat for a seating circle of 4 to 6 people, and fits comfortably within most backyard spaces without dominating the area.

Smaller fire pits of 24 to 30 inches are manageable for limited spaces but restrict log size and fire intensity. Larger installations above 48 inches require proportionally more fuel and clearance space and are better suited to larger properties with greater setback room.

Materials List

For an Unmortared Block Ring (36-inch inner diameter)

40 to 50 concrete retaining wall or fire pit blocks (standard 9x4x4-inch blocks)
Steel fire pit ring insert, 36-inch inner diameter, 3/16-inch or heavier plate steel
50 to 75 pounds of crushed gravel or sand for the base
Landscape fabric for the surround area
Pea gravel or crushed stone for the surround (optional but recommended)

For a Mortared Block Construction (same diameter)

All of the above, plus:

Fire-rated refractory mortar (do not use standard portland cement mortar, which can crack under thermal cycling)
A metal mixing bucket and trowel
A wire brush for cleaning block surfaces before mortaring

Step-by-Step Build Guide

Step 1: Mark the Excavation Area

Mark the center of the fire pit location with a stake. Attach a length of string to the stake equal to half the intended outer diameter of the fire pit (for a 36-inch inner diameter with 9-inch-wide block walls, the outer diameter is approximately 54 inches, so the string radius is 27 inches). Walk the string around the stake and mark the outer edge of the block ring with spray paint or sand. Add a further 12 inches outside this line to mark the excavation boundary for the gravel base beneath the blocks.

Step 2: Excavate the Site

Using a flat-edged spade, excavate the entire marked area to a depth of 6 to 8 inches. The goal is a flat, level base within the block ring area and a slightly deeper surround area where the blocks will sit. Remove all organic material, roots, and loose topsoil. A flat, compacted mineral subgrade is what you are working toward.

Step 3: Lay and Compact the Gravel Base

Fill the excavated area with 4 inches of compacted crushed gravel. Crushed stone compacts better than rounded stone and provides a more stable block foundation. Tamp the gravel firmly with a hand tamper or the base of a sledgehammer handle. This drainage layer prevents ground moisture from working up into the fire bowl and reduces frost heaving in cold climates.

Step 4: Set the First Course of Blocks

Begin laying the first course of blocks around the perimeter of the inner circle, checking for level constantly as you work. Use a rubber mallet to tap blocks into position and adjust for level. The inner face of the blocks defines your fire pit inner diameter, confirm this is consistent as you work around the ring. On unmortared builds, a tight fit between blocks is important for structural stability.

Step 5: Build Up the Courses

Stack the second and third courses of blocks, offsetting the joints by half a block length on each new layer. This overlapping bond pattern is what gives the structure its lateral strength. Three courses of standard 4-inch-tall blocks produces a fire pit wall height of 12 inches, which is a practical minimum for wood burning use. Four courses at 16 inches provides better containment for larger logs and a more substantial visual presence.

For mortared builds: Apply a 1/2-inch layer of refractory mortar to the top face of each block before setting the next course. Allow the mortar to cure for at least 48 hours before the first fire.

Step 6: Install the Steel Ring Insert

A steel ring insert placed inside the block surround protects the block faces from direct flame contact, which can spall concrete blocks over time. The insert should fit snugly against the inner block faces and rest on the gravel base. A 3/16-inch plate steel ring is the minimum recommended thickness, heavier plate (1/4-inch or 5/16-inch) will last significantly longer under repeated use.

The insert also makes the fire pit significantly easier to clean. Ash accumulates inside the steel ring and can be scooped out cleanly without disturbing the surrounding structure.

Step 7: Finish the Surround

The area immediately surrounding the fire pit should be finished with a non-combustible, stable surface. Pea gravel or crushed stone backfilled around the outer edge of the block ring and extending 3 to 4 feet outward creates a fire-safe perimeter that catches any embers that escape the bowl. Lay landscape fabric under the gravel to prevent weed growth beneath the surround area.

First Use: Curing the Fire Pit

Whether mortared or unmortared, all new block fire pits benefit from a curing process before the first full-sized fire. Start with a small kindling fire that burns for 20 to 30 minutes, then allow the structure to cool completely. Repeat this process two or three times with progressively larger fires before burning at full capacity. This thermal cycling process drives moisture out of the blocks and mortar gradually, reducing the risk of cracking from rapid steam expansion.

Connecting a Propane Burner to a DIY Fire Pit

A DIY block-built fire pit can be converted to propane by fitting a gas burner ring and running a flexible hose to a concealed propane tank. The burner ring sits on the gravel base inside the steel ring insert, and lava rocks or fire glass are placed around it in the same way as a manufactured unit. This approach requires that the gas connection be made with a regulator and hose assembly rated for outdoor use, and that the tank is stored in a ventilated location outside the block surround. CSA or UL-listed burner kits designed specifically for DIY fire pit installations are available from most fireplace and outdoor living retailers.

Safety Checks Before First Use

Before lighting the fire pit for the first time, confirm the following: clearance from all combustibles exceeds 10 feet in all directions; a garden hose or fire extinguisher is within reach; the spark screen fits the inner diameter of the ring; and any local burn permit or notification requirements have been met. The fire pit safety tips for homeowners guide provides a full pre-season checklist covering all of these points.

Part of the Patio Fire Pits hub. See also: Fire Pit Safety Tips | Best Surface to Put Under a Fire Pit | Fire Pit Ideas and Seating Layouts