[adil.hoxha]

Going to build a firepit in the centre of a 18' diameter stone patio. Any size guidelines on the firepit? Also wondering about the base of the pit - do I just need gravel/sand in the base to ensure drainage? I've also heard some people say I need to worry about venting the pit - not sure if it is necessary and/or how I would do it (PVC pipe under patio until it reaches some fresh air?). Welcome any ideas/advice from people who have done a firepit before...

Thanks

[Stonehenge]

I'm a bit nervous giving a homeowner information about constructing a fire pit, so I think rehashing a portion of the terms of use would be relevant:

We cannot and do not vouch for or warrant the accuracy, completeness, usefulness or efficacy of any posted information. Actions taken by anyone based on information in the GTX forums is the sole responsibility of that person. Each person shall be accountable for his or her own actions, and solely responsible for determing the efficacy and safety of the information provided. You agree to hold harmless GTX and it’s officers, members, assigned agents and employees, and all forum members, from any claims of physical, property or financial damage. This further includes any lost wages or productivity.

[Stonehenge]

With that being said, using plastic PVC as a vent for something where there will be fire seems like a bad idea.

I don't know what your design is, but I have yet to include ventilation in any fire pits we've constructed. Straight up there's as big a vent as the fire needs.

Re: size of firepit - ours are typically 30"-36" in diameter.

Re: stone for drainage - being able to clean out ashes might be more important than drainage, so I'd line the bottom of the fire pit with fire brick instead of gravel. Firebrick on the sides, too.

Hope that helps. Be careful.

[adil.hoxha]

Thanks - I thought the same about the venting - a little overboard. I'll look into the "fire rock".

[Fine Edge]

Ditto what Stonehenge just said. We're actually starting on one about the same size later this week and are building it exactly like he quoted.
Firebrick lining the inside, a row or 2 of cull brick & then our stacked stone outside.
Firebrick floor for easy clean -up. Water will evaporate but my clients don't want to replace their gravel every time they clean out their firepit.

[Fine Edge]

And please start a fire the conventional way. No gas please!!!

[VoodooChile]

Are you guys setting the fire brick at or below grade?

If the bottom of the pit is lined with firebrick, couldn't a coarse stone be placed under the brick, draining into Schedule 40 tile that isn't directly under the pit?

My concern is that standing water in the bottom of the firepit could compromise the base of the fire pit wall.

We are building two this summer, thus my interest...

Thanks!

[Stonehenge]

I haven't found that to be an issue.

[PSUscaper]

I learned from a friend to be careful with the stone coping if you are going to do that on top. He had a client that was burned becasue the stone around the top got so hot it 'popped' like when you torch it and threw a amber on his arm burning a hole through his sleeve and into his skin.

Not sure if it was just that particular stone that had a low heat point or a all stone.

[adil.hoxha]

Any links to "firebrick"?
I called a couple of suppliers (including the guys who sold my unilock pavers) and they didn't know of it. (One had a firepit base rock...nothing for around the sides.)
Any help on finding the right stuff would be appreciated - don't want anything "popping" on me or my guests

[VoodooChile]

Stone,
On one of them it won't be because it is elevated...

but on the other one the patio is old flagstone, maybe circa 1950. It sits below the existing grade of the lawn around it and has flagstone path running downhill onto it. We plan to tile a downspout that previously terminated onto the flagstone path, but given the grading, it seems reasonable to expect a large amount of water to wind up trapped on the patio and seeking the lowest point, the fire-pit.

Maybe the solution is a French drain that terminates into a tile a few feet from the center of the pit, outside its walls and away from the heat????

[Stonehenge]

adil - contact a face brick supplier near you instead of a paver supplier. Likely every wood burning fireplace in your area was made, in part, with fire brick. They should be easy to find.

Voodoo - since you're going to be tearing some or all of this stone out anyway, can you just pitch it away from the center, then have a trough of stone below grade around the outside, feeding a pipe or geotex-wrapped stone channel to some other place?

The only time I've ever seen a problem with water in a fire pit was a neighbor who'd dug his in at darn near the lowest point in his yard, all clay, and pancake-flat paver area around the pit. For a couple days after a good rain, he had a good amount of water in there.

[ctr]

A couple of thought: What's under the stone paito? Should be "mineral earth" (a technical term describing excating for fighting wildfires) that's nonflammable. If there's soil underneath, make sure it's not rich in compost or organics. If you build a long fire (say for a 36 hour pig roast) the compost matter can smolder and spread to outside your patio area; to your porch, leaf pile, etc. You won't know it for several days. Pine trees in the area would be a warning flag. Needles don't decompose, and can smoulder/burn readily.

I like the fire brick idea, but they may absorb water. The scenario that PSUscapes described may have been from a rock that had internal moisture. When heated up the rock can explode. I always thought it was an old wives tale from my scouting days till I read his account. Fire brick in the bottom will contain the heat, maybe you could get a cover or let it sufficiently dry before using. Don't take the wrong way, but using plastic for anything fire related???!? That Stonehenge is a wise man. He was a lot more polite than I would have been, so I'll let it go. Good luck