Backyard Skatepark

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Old 05-31-15, 12:01 PM
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Backyard Skatepark

I am about finished digging a large hole in my backyard that I plan to line with concrete and make a skate bowl so I can ride my skateboard in it. It is 23 feet long and 14 feet wide which I know is a big hole to have in my backyard but makes for a smallish skate bowl. This bowl is meant to last only a few years as I am 50 and don't think I will be down for skating many more years (although ironically when I skate I feel great and after playing a few sets of tennis, I hurt and walk funny for two days). This project is totally low-budget so I dug it out myself by hand and I plan on using a minimal amount of concrete.

I dug out the hole and piled the dirt around the edge of the hole so as I dug down, the sides went up. The hole is only about three feet deep but when I stand in the hole, I (a six-footer) can barely see over the top of the dirt piled up along the rim. I'm doing this because (1) a want to have a deeper bowl with less digging, (2) I want to avoid dirt disposal, and (3) when I do tear this thing down in a few years, I plan to chop up the concrete, remove it, and simply push the dirt back in the hole.

Speaking of the concrete, I am planning on pouring it only an inch and a half thick so that (1) I will spend less money on concrete and (2) when i remove the bowl from my backyard, I will have an easier time cutting up the concrete for removal.

I know it is recommended that concrete be four inches thick but I noticed recently that the people who poured my driveway decades before I purchased the house skimped and it is significantly less than four inches thick ( and has no rebar) and does not have significant cracking. It occurred to me that if my driveway was only a couple inches thick, something that I skate on could certainly be thinner than four inches.

I plan to use crack resistant concrete (Quickrete commercial grade crack resistant concrete in the orange bag) that claims on the bag to be capable of being applied only two inches thick. I'm going to push that and go an inch and a half or maybe only an inch since no cars will be driving on this concrete. I know skate bowls don't ordinarily have joints, but I also plan to put joints here and there to minimize cracking. I'm also thinking of filling the joints with some kind of compound that will smooth them out to make the surface more skateable.

I don't plan to go to the expense and trouble of using rebar, but I do have a large amount of wire mesh (heavy gauge wire that forms a grid with roughly four-inch squares) that was used as a fence until my neighbor and I replaced it with a cinder block wall. By the way, I had no know-how on that project. He knew what he was doing and I was unskilled labor just trying to help out and pull my weight. We got it done (70 feet long by six feet high paying only for materials because we did all the work ourselves) for
$1400 total. Maybe I can get him to help me on the pour of this bowl. But I digress. Long story short, I'm going to use the old wire fencing material as reinforcement. Whether or not it will be beneficial is debatable.

In spite of this effort to prevent cracking, I actually don't think it will be the end of the world if it does crack. If I get cracks, I will smooth them out if necessary and fill them in. This project is a practical one, and aesthetics are not important. I plan to color the concrete brown so it blends in with the dirt surrounding it keeping it stealthy for many reasons. Any patching I have to do to repair cracks will be colored similarly and will only add to a camouflage effect.

I'm also going to put a couple drains in the two deepest portions that will send water down to containers beneath the bowl. These containers will have pvc pipes coming out their sides. These pvc pipes will go underground sideways until they are no longer under the bowl and then they will curve gently and come to and out of the ground next to the bowl. Water that accumulates under the drains (and when it rains and these containers overflow, leaving water on the bottom of the bowl) will be pumped out through the pvc pipes. I will keep it dry because I don't want mosquitoes reproducing down there.

I also have a plan to secure a heavy chain inside the bowl to render it unskateable when Iím not home but Iíll spare you the details on this.

So I'm posting all this to see if anybody has an opinion of the project's feasibility. Am I crazy for trying to pour such a thin layer of concrete? Is it going to crumble under my wheels? Do you see any pitfalls that I may not anticipate? Any help would be appreciated.
 
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Old 05-31-15, 12:11 PM
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Welcome to the forums! I am a naildriver, with some concrete experience and absolutely no experience with skateboarding. Our concrete pros will chime in, so be gentle with them Such a thin layer of concrete probably won't last too long and you will be constantly be patching the cave ins. How do you propose to run the concrete 3' up the walls? Concrete will naturally want to slump. Your drains seem like a "permanent" solution to a temporary park. They will be a bear to dig up later on.

Oh, you will have about 14 years before your first knee replacement, so enjoy while you can.
 
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Old 05-31-15, 01:00 PM
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Boy It sounds like a wonderful dream but loose fill and thin concrete with no steel reinforcement just sounds like trouble. Bridgeman will hopefully chime in but even for a semipermanent project I wouldn't bet on it.

Unless you carefully compacted the soil as you built up the perimeter I think it will still be settling when you demolish the structure years from now so you can't count on it for much support. It may work as as a form but I wouldn't rely on it to support your concrete. I think you'll be in store for more than cracking that simply grinding could remedy. If you said you had tons of rebar lying around and were going to reinforce the snot out of it I might feel differently I might feel differently but I think the root problem will be all the loose soil piled up around the edges.

Perhaps this is an opportunity to get into a different type of skateboarding? Maybe you learn new tricks on a board that doesn't need a smooth concrete surface.

 
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Old 05-31-15, 02:34 PM
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My first thought was, better hope your homeowner's insurance carrier doesn't find out.
 
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Old 05-31-15, 07:52 PM
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Many (most?) of us old geezers can tell you that the human body starts to fall apart exponentially after the age of 60 or so. Meaning you'll be lucky to get 10 years out of this project before your body tells you to take up checkers, or some other non-strenuous activity.

But if you insist on proceeding with this project, here are a few things to consider. It requires a considerable amount of concrete finishing skills to smoothly place and finish a skating bowl. It's a totally different game than conventional flat work. And installing wire mesh in a total thickness of just an inch of concrete will also be very challenging, with the mesh either wanting to spring out of the rapidly-setting concrete, or remain completely buried, rendering it useless. Also, you'll have a ton of cold joints between batches of Quikrete, which are not the easiest things to finish smoothly, either.
 
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