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How To Successfully Build A Gas Fire Pit Part 2 – The Fire Pit Structure

Anatomy of Typical Fire Pit Structure

Welcome back to our new series about How To Build a Successful Gas Fire Pit.

In Part 1, we highlighted the importance of calculating how much gas is available for your fire pit project and what size pipe you need to get the gas to your fire pit.

We make those calculations first because the burner’s size may well dictate the fire pit structure’s size from an aesthetic point of view.

For example, the original idea may have been for a 4-foot diameter fire pit with a 36-inch burner in the center. But having discovered there is only enough gas for a 24-inch burner, it may look better to reduce that 4-foot fire pit down to a 3-foot diameter structure.

This series of articles in ordered so that the correct decisions are made at the right time. If you have not read Part 1 yet, it would help to take a look at there first before continuing reading Part 2

The Fire Pit Structure

At first glance, it would seem as if the fire pit structure is just some construction that holds the fire pit tray and burner in place and hides all the ugly plumbing.

True, but see what one of the industry’s leading manufacturers has to say about installing their brand of burners into a fire pit.

Failure to properly vent the enclosure may result in the fire pit overheating or explosion.

Venting the enclosure is so important that their Lifetime Warranty on a burner is void if there is no ventilation of the fire pit enclosure.

In fact, every manufacturer of fire pit burners stipulate that the fire pit structure must be vented. Venting is also regularly required to comply with Building Regulations and Codes.

Anatomy of Typical Fire Pit Structure
Anatomy of Typical Fire Pit Structure

What is Venting?

The concept of venting a fire pit structure or enclosure is simply to provide a `through draft’ of fresh air into and out of the fire pit structure.

Fire Pit Structure Ventilation
`Through Ventilation´

There are a few reasons that this needs to be provided:

  1. Overheating – as we have already mentioned, overheating of the equipment fixed inside the fire pit structure can cause damage. The constant `through draft’ of the enclosure replaces the hot air collecting within the structure with cooler air from outside, thus protecting the equipment from overheating.
  2. Gas Leaks – there are multiple gas connections within the enclosure of a typical fire pit. In the unlikely event that there was to be a gas leak from one of them, the `through draft’ blows out the collecting gas and helps prevent a potentially dangerous gas cloud buildup.
  3. Propane – propane fire pit burners have an Air Mixer Valve attached to the bottom of the burner, which means the air mixer valve is situated inside the enclosure. Air Mixer Valves mix air in with the Propane as it passes through the Valve. If the enclosure is not vented, then the air being sucked into the Valve is not being replenished, and quite quickly, it will be `suffocated,´ which will have a detrimental effect on the flame and produce lots of soot. 

It is important to highlight that, providing manufacturers instructions are followed, modern gas fire pits are inherently safe.

How Much Venting is Required?

The amount of Venting required may vary from different manufacturers and the type of ignition systems installed. The manufacturer’s instructions will provide the exact details. However, there is a consensus on the absolute minimum amount of venting to be provided:

  1. The enclosure must incorporate at least two vents to allow heat and or residual fuel to escape. 
  2. Some enclosures may require more ventilation based on material, size, and extended use.
  3. The vent may also work as a drain when installed at the bottom sidewall to prevent water buildup.

Vent specifications:

A minimum of two vents (18 square inches for each vent) on opposing sides of the enclosure totaling 36 square inches is required

-(example: 3-inch x 6-inch or larger). Alternatively, multiple vents uniformly made throughout the enclosure totaling 36 square inches or more of free area are acceptable.

· It is recommended to install the vents in the mid-to-lower area of the enclosure.

Venting Summary

Fire Pit Structures must be hollow and provide sufficient ventilation ( a minimum of 18 sq inches on two opposing sides of the structure ).

Selecting Your Gas Fire Pit Location

Clearance Diagram
Clearance Diagram

Wood Burning Fire Pits are very aggressive and uncontrollable, so they need to be located well away from pretty much everything!

Gas Fire Pits are much more controllable, and we have greater versatility in respect to where they can be installed. 

However, some consideration must be given to their location, particularly regarding their proximity to flammable materials.

Building Regulations and Codes often have rules about proximity to flammable materials, as do the fire pit equipment manufacturers. It is often the case that the recommendations differ.

In that case, always follow the guidelines that require the greater distance from flammable materials.

For example, if the Codes require 6 feet clearance and the manufacturer recommends 4 feet of clearance, you should comply with the Codes recommendations.

Conversely, if the manufacturer recommends 6 feet clearance, and the codes only recommend 4 feet, you must follow the manufacturers’ recommendations.  

Important Note: Clearances increase with the size of the burner to be installed. For example, HPC Fire recommends 84″ of clearance above a sub-200k BTU rated burner. Above 200K BTU that increases to 120″.

The Fire Pit Structure – Other Things to Consider

Drainage: The structure needs to have drainage. If you install the Venting at the very bottom of the structure, it can double as drainage. If the vents are not at the base, then some form of drainage is required to prevent the structure from filling with water during rain.

Fire Pit Structure Drainage
Fire Pit Structure Drainage

Access: Inside the fire pit enclosure, there are multiple gas connections, and depending on the ignition system used, there are potentially many other pieces of equipment. Easy access to the inside of the enclosure is essential for maintenance and repairs if and when required.

Drop In or Flat Pans Create Easy Access
Drop In or Flat Pans Create Easy Access

Gas Valve: Fire Pits must have a gas shut-off valve installed in an easily accessed position on the fire pit structure.

Fire Pit Structure Shut Off Valve 1
Fire Pit Structure Shut Off Valve 1

Conclusion

Irrespective of the shape and size of your planned fire pit, its structure must make provision for:

  1. Venting
  2. Proximity to flammable materials
  3. Drainage
  4. Shut off valve
  5. Easy access to the inside of the structure for maintenance and repairs

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