How to Choose a 36-Inch Smokeless Fire Pit Insert

On this page (7 sections)

1. How do you measure a masonry pit for a 36-inch insert?
2. Does a 36-inch insert need space around it?
3. How do you choose insert depth and shape?
4. What should you check before installing an insert?
5. Which products help compare outdoor heat options?
6. When should you choose another fire feature?
7. What is the final fit check for a 36-inch insert?

A 36-inch smokeless fire pit insert needs to fit the inside of your existing masonry pit, with enough clearance for its designed air openings to work. Measure the pit’s opening and depth, then compare them with the insert’s installation requirements before buying.

For indoor safety limits, see smokeless fire pit guidance.

The number in an insert’s name may describe its nominal size, not the exact outside dimensions. Confirm the measurements and required clearances for the specific insert you plan to use.

If you're comparing a built-in insert with other outdoor heat options, start with our fire pits and heaters guide. For a new masonry project, read how to build a fire pit before choosing the insert.

How do you measure a masonry pit for a 36-inch insert?

Measure the clear inside opening, usable depth and shape of the masonry pit. A nominal 36-inch insert will not fit every pit described as 36 inches wide.

Measure the opening from inside edge to inside edge in at least two directions. If the pit is not perfectly round, note the narrowest span and any ledges or uneven joints that could block the insert.

Measure depth from the intended support surface to the top edge. Check where the insert’s rim will sit and whether it can rest evenly without rocking or being pinched by the masonry.

Write down the measurements before shopping:

Do not assume the outside width of the masonry equals the insert’s fit size. The wall thickness takes up room, and the insert must fit the clear opening rather than the outer footprint.

Does a 36-inch insert need space around it?

Yes, the insert needs the clearance and airflow its design specifies. A tight fit that blocks air openings can affect how the insert operates.

Some smokeless designs move air through openings around or within the insert. If masonry covers those openings or closes off the intended air path, the system may not work as designed.

Check the manufacturer’s installation instructions for required gaps, support points and whether the insert can contact masonry. If the instructions do not cover your pit’s construction, ask the manufacturer or a qualified installer before lighting a fire.

Do not fill an air gap with mortar or other material unless the insert’s instructions call for it. Also check that the insert’s rim will not leave an unstable edge or create a place where hot material can fall into the masonry cavity.

How do you choose insert depth and shape?

Choose an insert whose shape and depth match the opening and support area. A 36-inch round insert may not suit a square masonry pit, even if its width appears close.

Compare the insert’s full dimensions with your measurements, including its rim, base and any parts that extend below the rim. A shallow insert may sit too high, while a deeper one may run into the pit floor or leave too little room beneath it.

Look for a stable resting surface that supports the insert as its instructions specify. An insert should not teeter on uneven brick edges or depend on loose materials to stay level.

For more options and selection points, see our guide to the best smokeless fire pit insert. If you want to compare metal insert styles, browse our best metal fire pit inserts.

What should you check before installing an insert?

Confirm fit, support, airflow and safe clearances before the first fire. Follow the instructions for the specific insert and your masonry setup.

Check these points before installation:

1. The insert’s actual dimensions fit the opening and depth.
2. Its support surface is level and stable.
3. Required air openings remain uncovered.
4. The insert has the clearances its instructions require.
5. Nearby walls, furniture, roofs and plants meet the fire safety guidance for your location.
6. Local fire rules allow the planned use.

Fire rules can vary by location and conditions. Check current restrictions before lighting a fire, and keep a suitable way to extinguish it nearby.

For deck placement, see wood-burning fire pit guidance for decks.

If you are making a new setup around a smokeless insert, our how to build a smokeless fire pit guide explains the design considerations. A freestanding pit or table may make more sense when an existing masonry opening cannot provide the required fit or airflow; compare fire pit table sizes and the best fire pit tables.

Which products help compare outdoor heat options?

These products illustrate different outdoor and indoor heating formats, but none of the dimensions establish a fit for a 36-inch masonry insert. Use them as alternatives to compare, not as insert replacements.

When should you choose another fire feature?

Choose another fire feature if the insert cannot fit securely or its airflow requirements cannot be met. If a DIY gas option is your plan, see build a propane fire pit.

Do not force a nominal 36-inch insert into a smaller opening or alter its air path without manufacturer guidance.

A freestanding fire pit can avoid masonry fit questions, while a fire table may suit a patio where a built-in fire is not practical. To compare other outdoor heat options, see patio heaters vs fire pits.

Compare the footprint and placement needs of each option before deciding.

What is the final fit check for a 36-inch insert?

Choose a 36-inch insert only after the measured opening, pit depth, support and airflow all match its instructions. If one of those points is uncertain, confirm it with the manufacturer or a qualified installer before lighting a fire.