We found this great how to Fire Pit swing at http://www.instructables.com/ that we thought you might enjoy. As always Tanco Lumber Associates are available to help you with you project materials list. Enjoy!
Step 1: Picking the Site
You will want to start with a level area that is maybe 5 feet larger than the structure you intend to build in every direction, or about 25 feet across if you stay close to the dimensions here. If it isn’t perfectly level, that is OK, but you will want to level it AFTER you build the structure. It makes no sense to level first only to have to dig deeper holes for the posts.
In my case, I had a giant old swing set that I built about 14 years ago when my youngest daughter was born. Thanks to Craig’s list, it was gone in 3 days and I got a little cash to use towards this project.
Keep in mind that, depending on where you put it, this structure can be used year round and it will only be used with a fire for a fraction of that time. My teenage kids wander down to sit on the benches during the day with their friends and sometimes even go down there just to study or read. Fortunately, we have trees to create both morning and afternoon shade, but no trees immediately over the fire pit.
So if possible pick a spot that gets shade for much of the day but it cannot have tree branches directly overhead.
Step 2: Materials and Tools
Grass seed or sod to cover any remaining bare dirt.
You will also need:
You will also need to rent a 2-man power auger and an 8 or 10 inch auger bit with an extension. Ask a friend to help with the auger. I used a 1 man auger and it practically killed me. Not recommended. Oh, and DO NOT ask your wife to help with the auger. Trust me on this.
Step 3: Measurements, Angles and Markings
I am a pretty experienced DIY builder but had never tackled anything that didn’t have square sides. This is a hexagon. 6 sides. Plumbing and trueing a hexagon can be a little daunting, so here’s how I tackled it. I measured everything from a center point using OUTSIDE dimensions. The only time I used on-center (O.C.) measurements was when measuring the distance between posts along the outside.
With hexagons, the distance from the center point to the outside edge of each post will be a little less than the length of each beam. My beams were 8 feet long, and the distance from the center point to the outside edge of each post was 7′ 11″. So the beams opposite each other were 15′ 10″ apart. Don’t dwell on this too much as the easiest way to measure your hexagon, regardless of the beam length you choose, is below.
The other thing you need is the angle of the cuts for your beams. 360 degrees divided by 6 is 60 degrees, split between the two ends of each beam is 30 degrees. So your cuts will be 30 degrees on the end of each beam.
To make the dimensions as easy as possible, I went ahead and cut the beams and laid them out on a flat surface so I could take all the measurements directly from the beams. You have to be a little more exact when digging holes and sinking the posts, but cutting the beams first ensures that your structure is symmetrical. Just make sure that your beams are perfectly parallel on the ground before you start taking measurements. All corner to corner measurements should be the same and all beam-to-beam measurements should be the same. While you have the beams on the ground, mark the center point of each beam so you will have a reference for the cross-braces. Number both sides of each joint 1 through 6. And save some of the 6×6 scrap pieces for later.
Now, making your hexagon square and level is going to be a challenge and you do NOT want to have to lug these 6×6 beams around anymore than necessary. So, I cheated. Once I was satisfied with the beams, I cut the 2×6 boards that I would eventually use for cross braces to be exactly the same dimensions as the 6×6 beams. Now you have much lighter boards to work with as surrogate beams. When you are done with them, you will cut about a foot off of them and use them as cross braces. Nothing wasted.
While you have the saw out, cut one of the 2×2 boards into 1 foot stakes with a 45 degree angle at one end. These will be used as anchors later.
Step 4: Laying out for the posts
To create a grid for my layout, I put a steel rod in the center of the space, measured out the length of my beams (8 feet in my case) and painted a circle. That was a good starting point. The posts will end up just inside the circle.
Start with the “front” of the hexagon and either lay down one of your 2×6 mock-up beams or measure out the dimensions and paint the ground where the posts will go. If you saved any 6×6 scraps, place one where each post will go just for the visual and to help with measurements.
When you are done marking out for the six posts, the marking for each post should be exactly the same distance from the center rod and exactly the same distance apart. I used a field tape-measure with a large hook on it so I could walk to each post location without having it unhook from the center rod. Don’t forget to make sure the corners are all the same distance apart (measure the post markings across from each other and make sure the beams will be parallel). This may sound complicated, but once you start laying things out, it isn’t. If you painted a circle at the beginning of this process, all of your post marks should be the same distance from the circle as well.
Step 5: Setting the posts
OK, time to go get that power auger.
You will want to auger the holes exactly above your marked locations for each post. Make sure the hole is straight. Start without the extension and drill all 6 holes. Then attach the extension and go back around and dig down to just over 3 feet. 3 feet is building code frost-line depth where I live. It is also deep enough to ensure that the structure is rock solid.
Here is a hint. If you have really nice grass that you don’t want to destroy AND your yard is perfectly level, use a couple of sacrificial tarps over the auger hole. Cut a hole in it and let all the dirt from the auger fall onto the tarp. This keeps the dirt out of the grass and allows you to haul any that you don’t use away.
Note: If your location is not perfectly level, you will want to dig to 3 feet on the HIGH side. Use the string and line level to determine how many inches shallower each hole on the low side will need to be. You will end up with all posts at three feet deep into the ground once you level the area with additional dirt.
Take one of your 2×2 braces and mark it at 2 and 3 feet. This will be your depth gauge as you auger.
Mark each 6×6 post at the three foot mark. I also marked each post at the 6 foot mark to make leveling a little easier.
Now, there are a couple of ways to set and level posts. You could set them and then cut off the tops to make each level, but I wanted to use all 10 feet of my posts, so I actually leveled each post before setting it in concrete. It isn’t as hard as it sounds.
Start with the depth gauge and dig each hole so it is maybe 3 feet two inches deep. Don’t be lazy here. When we get to the leveling step, it will be a lot easier to fill a hole in a little than it will be take things apart, pull a post out and dig more. Pour some paver base into the hole and flatten out the bottom so the hole is at or just over 3 feet deep.
Drop a post into each hole and check to see where that 3 foot pencil mark you made is. It should be at or slightly below grade or where you expect it to be if the area is not perfectly level. Be careful when placing or removing the post so you don’t collapse the sides of the hole. These posts are heavy, really heavy, so either have a friend help you or pretend you are a Scottish pole thrower and be prepared for back pain later.
Get the posts as close as you can to level. One good way to do this is to tie a string to one of the posts at the 6 foot mark that you made earlier (This will be 3 feet from the ground now…). Attach the string level to the string and walk to the 6-foot mark on each of the other posts. We will get them perfectly true and level in the next step.
Step 6: Trueing and Leveling the posts
Leveling and trueing the structure will take a little time and patience. There will probably also be head scratching.
Again, there are several ways to do this. My technique might not be the absolute easiest, but it turned out pretty well.
Remember those “cheater” beams we made out of the 2×6 boards? Get those out and set them on top of each post. Screw each side into the top of the posts with two deck screws. The position of the cheater beams should be consistent across the center on all posts. In my case, the ends of the cheater beams (points) just stuck over the outside of the posts by about 1/2 inch.
Now take the 2×2 braces and screw one to the top of each post. Hammer in the anchors next to where the brace touches the ground but do not attach them yet. You have some extra braces to use if you need to anchor a couple of posts from two directions.
Time to measure everything again. Make sure that the cheater beams have exactly the same dimensions that you recorded for the beams you cut and laid out on the ground. They should be completely true but do not yet need to be perfectly level.
Once the hexagon is true, screw the bases of the braces into the anchors. You might need to anchor one brace, check dimensions, then anchor the next. The goal here is to make the hexagon perfectly symmetrical a tthe top. The poles themselves can be a little crooked.
Ok, now that the top of your structure is symmetrical, you can use the post level or box beam level to ensure that each post is perfectly straight. You may need a little leverage to move the bottom of a post an inch or two. Use a shovel or a rock-breaking rod. Do not forget to check the beam measurements each time you move a post to make sure it is all still true.
Once the posts are straight, you can level. I did this by setting my 8 foot box-beam level on top of each of the cheater beams. For low posts, pour in a little paver base and lift up the post to allow the paver base to flow under it. You may need to disconnect the brace so you can lift the post.
Keep leveling all the way around the structure until all of the cheater beams are level. I ended up with one that was about an inch high and decided not to pull the beam out to dig more. Only I notice.
Once you have the post-tops level, measure all of the beam dimensions again. Chance are good that something moved slightly. Adjust and reattach the braces as needed.
Once everything is true and level, pour a little gravel or paver base into each hole to ensure that there is drainage at the bottom of each post and that the post isn’t going to move as you pour concrete.
Mix and pour the concrete one bag at a time. Pour it in evenly, then jam the concrete in around the post with the iron re-bar you used as the center marker. The concrete should stop at or just a little below grade. Angle the top edge of the concrete so it will channel water away from the post. Let it dry overnight.
Step 7: Setting the beams
Once the concrete is dry, you can take down the braces and the cheater beams. If you are going to stain the wood, you might want to hold off on grading until after you’ve stained.
Sidebar: If you have to grade the whole area to make it level, here’s an easy way to figure out how much dirt you need. Since your posts are level, there should be a “3-foot” mark a few inches above the ground on the lowest side of the grade. Measure how high that is from the ground. Take the distance between two beams across in inches and multiply that by two. That is roughly how many cubic inches of dirt you would need to cover the area with one inch of dirt. Now multiply that times the number of inches above the ground that the 3-foot mark is. Since this is a slope, divide that number by 2. That’s how many cubic inches of dirt you need. To convert that to cubic yards, divide it by 36, 36 again and 36 again. Round up. If it is already close to a rounded number, add a yard. Example: 10 inches from ground to “3-foot: mark. 16 feet across. 192 inches. 192×192=36,864 ..x 10 inches = 368640 divide by 2 = 184320 divide by 36 = 5120 divided by 36 again = 142.2 divide by 36 again = 3.95 yards. Get 5 yards.
Wait until after you’ve stained (step 6) to grade the area.
OK, now is the time to look at your posts and clean them up a little if you want. Sand down any pencil lines, splinters or rough areas. I decided to use a router and a round over bit to radius all of the edges of the posts and the beams before they were installed.
The cheater beams you used before are perfect templates for the real beams in terms of where the lag bolts are going to go. Use the screw holes on the cheater beams as a template for the countersunk lag bolt holes on the actual beams. I countersunk my lag bolts about 1/2 inch. Drill holes in the beams that are the same diameter as the lag bolts but just drill a pilot hole down into the posts or use the hole made by the screws holding the cheater beams.
Set the beams on the posts in the order we numbered them before and place the lag bolts with washers into each of your drilled holes. Using the socket set, start cranking one side of the first beam into the post. Once it is in there a bit but before it is tight. Drill pilot holes for the 4” deck screws that will hold the beams together tight. Then screw in the deck screws. If your angles and posts are true, there will be no gaps between beams. Now finish ratcheting down the lag bolts, repeat this for each beam.
Step 8: Adding the cross beams
Remember when I said to mark the center line of the beams when you first cut them? Here is where that comes in handy. Set each 2×6 board so that it lays over the center line on two beams. Use a speed square or straight edge to mark the cut on each end of the board. The cut on the board should match the centerline on the beam. Number these boards on top so you can keep them in order. I suggest you cut each board one at a time and then place them on the structure to make sure they fit properly. That way, if you cut one board too short, you can cheat a little by cutting the next a little longer. You will also want to trim the outside edge of each board so it does not poke over the beam. That gives a much cleaner look.
Oh, and these boards have the same cut angle as the beams. 30 degrees.
For my structure, once all of the boards were cut and set on the structure for fit, I rounded over the ends with a router so there were no points or places to splinter.
When you are happy with the way these boards look, screw them in with 2 4-inch deck screws on each board end. The structure should now be rock solid and should not move at all.
Step 9: Staining, leveling and setting the fire pit
Now that the structure is all assembled, it is time to stain and level if your yard is sloped at all. Give every board another look to make sure there are no pencil marks left. Once stained, a pencil mark will never go away. To stain the structure, I used a quality deck stain and gave it two coats.
Once the stain is dry, grade around the base of each post and level the area as needed. (See the sidebar in step 4) I was on a gentle slope and needed to bring about 5 yards of dirt in to level.
I suggest that you place your fire pit as you level the area. This way you can level the fire pit first and ensure that the foundation for the pit is exactly at or a little below grade. If it is below grade, the foundation blocks will be completely hidden, giving the pit a nice clean look. Once you are happy with the layout of the fire pit, use landscape block adhesive to secure at least the top two rows of blocks to the rows underneath them.
I used large concrete pavers for the foundation and concrete landscape blocks from Lowe’s for the fire pit. I wanted grass under the benches and a small gravel area around the pit. I also ended up using slate that I shaped to fit. To finish it off, I purchased sod rather then having to wait for weeks for grass to grow in from seed.
Step 10: Installing the benches
To hang the swings, measure the distance between the chains on an assembled swing. Now go down to the structure and measure out from the center of each beam (where the cross brace sits) one half of the distance between chains. Mark those spots. Assuming you purchased through-bolts with lock nuts, you will want to drill through the beam in these locations with a bit equal to the diameter of the bolts. Insert the hanger bolts from the bottom, drop a galvanized washer on top and tighten down the lock-nut. (If you choose to use the lag eye-bolts provided with the swings, just drill pilot holes into the bottom of the beams at the correct locations and twist the bolts into palce with a large screwdriver or other tool that will give you some leverage. Repeat for all 5 beams where you want to hang benches.
To hang the swings, I used screw-down snap hooks and eventually added swing springs. Once you are sure the height is correct, cut off the excess chain so it does not rattle.
Step 11: Wrap it all up and enjoy!
Once everything is complete and cleaned up, find some dry firewood and light it up!
We placed Tiki torches just outside 4 of the posts to provide light. It is almost too much light.
Grab a beer or glass of wine, light a fire and congratulate yourself on a job well done!
I hope you find this Instructable useful! This project was a lot of fun and this unusual fire pit is both a terrific place to hang out and a great conversation piece!
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