Firepit Construction

[Chad Shaw]

Beginning to put together construction details for a firepit…it will be set near ground level (w/ 4-6″ curbing) in a concrete patio.  We need to account for some sort of retention in regards to keeping the concrete sub-base from spilling into the pit; drainage; and possibly ventilation.  Does anyone have any details that they would like to share?

[mark foster]

Hi Chad,

What part of the pit is set near ground level–floor or top?  Wood burning, or gas?

[Chad Shaw]

Top of pit is near ground level, and it will be gas…I have a pretty good idea of how we’re going to construct it, but just wanted to see if anybody had any suggestions for any particular scenarios we hadn’t considered.

[Jordan Lockman]

In wood fireplaces we would use well casing sections. They were almost free and worked great. Also at home in my wood fire pit I made ring with Firebrick and dry laid stone on top of that. It has worked well. Again these are wood fireplaces not gas.

[mark foster]

I am in a similar climate zone as you are (Louisville, KY), and open pits (of any kind) can become sumps and/or get pretty damp.

If the walls/floor of the pit are premanufactured in one piece, they can be pretty watertight and the entire thing could float if the ground water is too much–you would need to put drainage around it (clean gravel and soil separation fabric) and pipe out to daylight.  If the pit is hand built and a bit porous, you can put the drain in the pit bottom and pipe out.  We have some pretty heavy clay soils and high water tables around here, so I tend to go with making the pit walls/floor as porous as possible so that the hydraulic pressure is never an issue.  I never use “dry wells”–I have seen too many silt up and fail over time.

I assume by ventilation you mean for the fire?  I am not aware of any issues in an open pit.  Usually the problem with gas fixtures is too much wind.

[Thomas J. Johnson]

My main concern is that a concrete patio with a 4-6″ concrete fire ring sounds institutional, cold and unattractive. Are you giving the concrete any kind of finish to make it unique? I.E. Polish/grind the fire-ring and sand-blast the field to create a different texture while exposing the aggregate in both elements?

Also, with gas, you will need stone, glass, etc. to diffuse the flame, otherwise it will be like standing around your stove.

You can avoid a lot of the design issues you’re facing if you make the pit 18-36″ above ground. Drainage can happen through weep holes at the base, at grade. You won’t risk people tripping on a 4″ curb and getting injured by the pit. You will be able to feel the flames better if it’s higher and the structure can double as seating when the fire is off or you can make a seat/wall cap and sit on it when the fire is on… 

[Chad Shaw]

yeah, yeah, yeah….I was waiting for the trip hazard comment 🙂

The concrete will be stained, curb/ring around firepit masonry to match house, etc.- the finish details have been discussed, more interested in ideas to help make it work effectively at this point, not look pretty (but thanks for the recommendations).

[earthworker]

Unless you like scorched and cracked concrete, you had also better line the inside of the ring with some sort of fire brick.  A gas firepit will create sustained and intense heat that will stress concrete surrounding it.

[Scott Thomas Murison]

Consider a convex surface for drainage and keeping the fire breaking apart for extra oxygen supply. Slightly more wood would be needed for the session however.

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