Firepit construction/design questions (pics attached)

swervinvolleyerAugust 27, 2012

Hey all! I've attached a 'before' photo of my backyard firepit that is now in progress. Looking toward the back fence from my deck, my yard slopes from right-to-left. So, I decided (after thinking through it for months) to cut out a half-circle (into the elevating ground) and create a seating area (which I will fill with mulch -- at least to start. The left half of the circle (think 6 O'clock to 12 O'clock) will remain a grass seating area.

In regard to my next step, I'm going to take the firepit 'ring' down a good 14-18" or so -- as I don't want the fire raging above anyone. My questions are this:

* The dug-out trench area currently has a very slight slope

as it continues away from the home (think

counter-clockwise). Should I make this slope slightly

more pronounced and install a pebble-filled drain at

about 12:00? I thought I'd dig a 1' x 1' trench and fill

it with gravel for some drainage. This will be covered

with landscape fabric and mulch soon).

* I plan on planting some arbor vitae (or some other

evergreen hedge -- suggestions welcome!) around the outer

right-side ring. I envision doing a row starting at

least 1' outside of the edge of the 'cliff' -- just to

keep grass around the ring and make it look more

natural. Any other other ideas as it now stand (in

picture #2)?

I'll have more questions about the inside of the pit I plan to dig -- those will come as I get more into it. Now, time to get out and start taking down the current pit ring.

Thanks, and look forward to hearing some replies!

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Here's how it currently stands...

    Bookmark   August 27, 2012 at 1:15PM
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catkim(San Diego 10/24)

The prevailing winds will blow the smoke which way? Will people sit on the mulch on the ground or in chairs? Being more of a "plan ahead" kind of person, I would have measured and sketched this, and considered materials and permits before digging, but that's just me.

    Bookmark   August 27, 2012 at 1:56PM
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Swervin, this is a relatively simple project without much in the way of physical constraints. Keep it simple. Don't create any underground drainage. There's no reason that all of your drainage couldn't be surface flow. Seconding catkim, you need to provide a simple plan that shows your intentions... paving, seating, firepit, etc. Slap on some measurements and call out the materials. Show what's going to happen and get advice before you build in order to build problem-free.

    Bookmark   August 27, 2012 at 2:11PM
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karinl(BC Z8)

Any underground utilities?

Karin L

    Bookmark   August 27, 2012 at 2:27PM
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Did you check with your fire department about the fire pit permitting and regulations? They are pretty serious about that where I live.

Some people like to put an insert into the fire pit so that after the fire is out and you want to clean it out you can just pick up the insert and dump the contents. Just be sure it has drain holes so it does fill with water.

I am not really clear where you intend to put the arbovitaes. I you are going to plant them where the edge of the half moon of mulch is going to be, you might want to consider that fire pits don't always burn at the same temperature. Sometimes you want to be pretty close to the fire and sometime you want to be further away. I wouldn't put a constraint like a hedge on how far away you can get. Also it appears that the area I think you are talking about it close enough to the fire pit that trees would be a fire hazard. Additionally, arborvitae gets very large at maturity - they will not remain cute little trees.

    Bookmark   August 27, 2012 at 2:48PM
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deviant-deziner(Oh zone)

Drainage is always a concern and should be planned for when installing fire pits or patio surfaces , especially if they are set below the natural grade.

The type of drainage system is dependent on your soil conditions and profile , grade and climate. There is no one set answer. Each project has its own site specific answer because every site and the soil profiles are different.
Depending on the type of fire source different drainage systems are specified. In general terms , the systems differ from wood to gas.

In projects such as yours a basic master plan would be helpful in working out most of the answers to the questions before they happen. ..this will save money , time and produce a far superior end product.

For ideas and installation info on some great looking fire pits try the Taunton Press, Outdoor Idea book or the Outdoor Kitchens that Work book - ( despite the title of the later they have some nice looking simple fire pits )

    Bookmark   August 27, 2012 at 3:39PM
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Thanks for the early replies, everyone. Let me tackle the first go-round of answers:

* Yes, I am within code on this pit, and certainly double-
checked that before proceeding forward (I've had a pit
that came with a newly remodeled home, and have used it
for the last three years consistently)

* The winds blow from right-to-left across picture #2.
This pit is 20' from the house deck, 20' from the
nearest fence and shed -- or any other object

* I do have arborvitae already as a hedge on the side of
my deck. I think this particular species should grow to
between 8-10'. Can I keep the height at a certain point
once they get taller? If not, then I'd love another
suggestion as a privacy hedge (final resting height
would be perfect at about 6'.

* Guests will sit either on the grass side, or the mulched
side, and in lawn chairs. During dry periods, I plan on
watering around the inside ring before I burn any fire.

* As far as not measuring or sketching goes, I have done
that, albeit roughly. I like to make amendments as I go
along -- which I've already done. I'll certainly ask
for some more advice as I get further into it as well.

* No underground utilities. I've already dug about a foot
deep on the 'trenched' area, and probably won't got any
more deeper (just a few inches if need be). Good to go

* I should note that I don't do typical bonfires. My
fires are smaller, with 4-5 medium-sized logs at a time
(at most)

* Dimensions
* Outside border of the actual pit itself to
the 'cliff' of the trench is 12' (looks shorter than
this in the pictures). So, if I planted the
arborvitae at least a foot outside of the
trench, they would be 13' from the fire.


I've attached a picture post-concrete ring demolition. The old earth-rammed firepit at quite the concrete base under it. That was a doozy!

Thanks again for the replies, and look forward to hearing more input!

    Bookmark   August 27, 2012 at 3:49PM
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Deviant -- thanks for your reply. This firepit will be in ground/dug-out. Might be line the inside walls with some sort of stone.

I've attached a pic of what I've always sort of envisioned. That is granite, I believe.

    Bookmark   August 27, 2012 at 3:53PM
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Your last photo looks like a nice goal.

You're showing us a piece of what you're doing and telling about other pieces and asking questions about pieces that have yet to come into existence. What we're trying to comprehend, first, is your overall scheme. It would be easiest if you show us your rough sketch. (No one cares that it's rough or that you may make changes.) But after we grasp your overall intention, we can make suggestions about the drainage... that will probably simplify your efforts. After re-reading your posts, I can't grasp exactly what you're doing with slope. If you explained it simply on a sketch, it would be easy for you to do and for us to understand. Whatever you're doing, you don't want to fight the natural grade and create drainage that works in the opposite direction. Drain toward the lower elevation.

When you say "mulch" do you mean bark or stone? A stone product would be much more appropriate for a firepit. You need something that packs and can be easily walked on such as decomposed granite or crushed brick. Search Google images to see either.

    Bookmark   August 27, 2012 at 5:34PM
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Yardvaark -- thanks again for the reply. I've attached a VERY rough sketch. I'm no artist, and I'm still somewhat of a backyard novice -- though my knowledge is increasing by the day via these Gardenweb forums.

Hopefully this is clear enough for any/everyone. Thanks!

    Bookmark   August 27, 2012 at 8:08PM
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P.S. I meant a bark much -- at least initially. Haven't found the pebble/rock that really catches my eye just yet.

    Bookmark   August 27, 2012 at 8:59PM
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Swervin, it might be that my explanation is like directions to a card game where it's more difficult to understand the rules than it is to play the game. I'll try to clarify anything that seems "muddy."

Even though you'll have the firepit area be half grass and half "mulch," for the sake of simplification in setting the grade, think of it as all one material--like a large disk set flush into the lawn--as a patio. And in the beginning, think of its SURFACE, not its depth or thickness. (For the time being, forget about the central pit as its existence doesn't have significance for setting the grade surrounding the patio.)

Regardless of actual cardinal directions, think of my plan drawing such that UP is north. Since the grade is sloping downhill to the left (westward) you'll want to have the firepit patio slope in the same general direction to allow for the simplest drainage solution. (This presumes that the north/south slope is negligable; for the sake of this example, we'll think of it as level.) In order to avoid doing too much digging or needing to import soil for filling, you'll want to balance cut and fill by setting the SURFACE of the north/south axis of the patio slab--it's centerline (marked "C" in the drawing)--at the 0.0 elevation. This means you're neither raising or lowering the centerline of the patio surface relative to the surrounding grade. At the north/south axis, you're meeting the grade flush. (See "Exception" below.)

In order to achieve positive drainage across the flat patio slab, you'll need to tilt its surface so that it has approximately 1/4" drop per foot of run. (Think of it as a patio set flush into the lawn, sloping in the same general direction as the lawn. Since the lawn grade slopes a little more than would be comfortable to use for a floor for furniture, we're UN-tilting the patio slightly, so it FEELS more like it is level... even though it will actually slope enough to drain.) You'll set the EAST side of the patio about 1 1/2" to 1 3/4" HIGHER than the central ("level") north/south axis. You'll set the WEST side about 1 1/2" to 1 3/4" LOWER than the central axis. This will give you a 3" to 3 1/2" grade differential across the entire patio slab, and any water that lands on it will flow off to the west. (Water that falls on the ground east of the slab will flow onto the slab but then continue to flow across it and off of its west side.) Once the patio slab surface grade is set, you'll adjust the surrounding grade as necessary, blending it to meet the patio surface. It will be no more than a gentle slope, requiring no steps, gravel-filled drainage pits or retaining devices to stabilize grade change. You will only need to retain the granular patio material itself in order to keep it from migrating into the lawn. You should determine the patio material and what you will use to restrain its edge before you go farther into the project.

EXCEPTION: Besides the cut that you'll make at the uphill (east) side of the patio, the patio slab will require excavation to accommodate ITS OWN VOLUME. You'll need some place to put the extra soil that is removed for it. You'll need to make a calculation--best guess-- about the amount of earth that will be removed to accomodate its thickness, and raise the entire patio, SLIGHTLY ABOVE the 0.0 lawn level elevation at the patio centerline. (I'm guessing that you'll probably raise the patio surface another two or three inches; it depends on your material thickness.) In this case, half of your patio circle is grass and therefore has no thickness so, in theory, it will not require additional excavation for that portion unless you need to tweak its grade to blend it to the rest of the patio surface.

I would highly recommend NOT constructing the patio of wood-based material... not only because it has fire risk, but because it's an inferior surface where furniture is involved. Hard, granular material that packs down tightly will work better. Check out crushed brick as one option. There are other color crushed stone options, too. Don't use any gravel (such as pea gravel) that doesn't pack tightly.

The actual fire pit itself (as you show in your recent photo) is charming and you would want to copy the detail of how it flares up slightly above the surrounding grade... so as not to funnel rain water directly into the pit, but direct it instead around its perimeter where it can run off the patio surface with the rest of the rain.

I'm wondering how you'll treat the wedge shape areas that I have circled in red. Will there be grass there?

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    Bookmark   August 28, 2012 at 10:00AM
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Wow, I'm not sure where to start. Thanks for putting the time and effort into your last post. I appreciate you taking the time. I will post updates as I move forward with this. With holiday weekend traveling on the horizon, this project will be 'shelved' for a few days.

In regard to the mulched area -- part of my decision is based on the fact that I'm on a bit of a budget with this project. The bark mulch (particularly with the fall season sales) is going to cost considerably less than any sort of stone or gravel would.

Yes, there currently is grass in those red/wedged areas, and the grass will stay. At this point, there will just be a walkway up against the fence there.

Thanks again for the useful insight/mock-up!

    Bookmark   August 29, 2012 at 11:00AM
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Swervin, you're welcome. I hope you understood the explanation.

I don't know how you're buying and delivering materials. IF you have access to a pickup truck or trailer and can transport crushed stone material that way, it's not expensive. It's cheap actually. But if you don't/can't, I understand. We do what we must do. Be sure to use a landscape fabric to separate "mulch" from soil.

I question the tight semi-circular layout of the planting and the plant material choice. I think it may prove to be somewhat "engulfing" -- maybe even a little claustrophobic -- in the future. And I wouldn't care to have the grass "triangles" at the back and don't see the advantage to having a path behind. Is there any desire to extend the screening higher than what the fence currently provides? You might submit a measurement of the distance between fence and closest point to firepit patio.

    Bookmark   August 29, 2012 at 12:58PM
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