Sunken Trampoline

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About: Enthusiastic DIY kinda guy. More commonly known as a cheap skate in Scotland who doesn't like waste or spending money.

Hello,

We came across a trampoline that someone was giving away as they no longer needed it and thought that this would be a nice addition to our garden for our children to enjoy. Our only problem was that we have never enjoyed the look of a trampoline sitting in a garden or the care needed if you experience high winds. After some browsing online we discovered a nice way to incorporate it with your garden and remove some of the drawbacks of a standard trampoline.

Dig a big hole and leave it sitting flush with the ground providing easy access, enjoyable bouncing experience and somewhere to sunbath when the kids are at school. Sounds simple, right?

Supplies:

Step 1: Materials and Tools,

For this there would be much simpler ways to go about sinking your trampoline but i used what I had on hand and is an inexpensive way of doing it (and gave me a good few nights of sleep afterwards).

Tools:

Spade

Rake

Wheel barrow

Small metal fence (used as a sieve for the larger pieces of soil)

Materials:

Standard trampoline (just under 10ft)

100mm by 30m Damp proof course (any bit of thick plastic can be used to help retain the soil would be fine this was just what i had on hand.)

Wooden stakes (pressure treated)

3" pipe (to allow the air to escape)

Step 2: Trampoline,

Its final resting place,

The first step I took to planning this back garden project was to assemble the trampoline (as the children were nagging me and wanted a bounce) to visualise the size and were it might look best. I think you need to be certain of where you plan to place it as this could be its future home and filling your man made crater will be as much fun as digging it out was (something one should only do once in their life time).

Mark out its size,

Once we were all happy with the location after much talking of future garden plans we flipped the trampoline upside down and used the spade to mark out its shape cutting into the grass to give a thin outline.

Step 3: Start Digging,

Start to remove the lawn and dig out a shallow hollow around the perimeter of your marked out area, this gave me a good indication of the amount of work I was in for.

We used the wheel barrow and the small metal fence to sieve the larger clumps and to remove the biggest rocks.

More digging,

Once we had dug out enough of the top soil in a sort of step configuration to fit the trampoline in we moved onto the next step.

Step 4: Trampoline Frame and Retaining Wall,

After removing the middle leg bars from the feet of the trampoline to make it much smaller in height we placed it into our small hole, this took a few attempts to get it sitting flush with the grass to give it the look we desired.

Retaining wall,

Next we got our Damp proof course which was 30m long by 100mm so that can give us 3 wraps around our frame with enough to tie onto the near by legs.

Start from the bottom and work your way around the leg to give you a bottom layer, then move it up leaving a 10mm overlap behind the bottom layer and repeat for the third and final layer. Tie of one end and start to pull it all taught all the way around until all sides and layers are as tight as you can get, then I tied off the other end leaving a a flexible but stable retaining wall.

Step 5: Stake, Drainage and Airflow

I used some pressure treated wood stakes I had left over to add an extra support between each of the legs to help hold the retaining wall back.

More digging was in order, so I used some of the soil to sit against the wall from inside the hole and filled in the gap between the plastic wall and the garden.

I have also dug down an extra 30cm by 50cm wide in the centre and filled this with rocks and gravel which i reclaimed from the soil that was extracted. This is to provide drainage and is dug into the subsoil.

Once all of the digging was finished I decided I better try and take care of the air which is squeezed out when the trampoline is used. I tried to do this by placing four 3" drain pipes around the outside of the trampoline frame. Later on we discovered that it works fine when the children are bouncing on it but it doesn't allow enough air to escape for an adult which produces the green spring guard to flap up once per bounce. This doesn't bother us at the moment but I may go back to tackle this problem once an for all.

Step 6: Final Result,

Once all the hard work was done and 20 mins of wrestling with the springs we finally got a chance to see what it was going to look like and have a go.

I would suggests bouncing slowly and work your way up just to make sure you have dug more than enough soil out to give you the clearance that you need.

Our children have loved it and it really was worth the time. It took myself one and a half days to do it all which included stopping to play with the children during breaks.

Where did the soil go?

Luckily for us our front and part of our back lawns were both uneven and we used this as an opportunity to level them off and re seed the bits we made level. We have also piled some up behind as you can see in some of the photos and I plan to build a retaining wall out of some reclaimed bricks which will be another instructable which I intend to make.

Thank you for reading and I hope this will help anyone who wishes to take this challenge on.

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    18 Discussions

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    techydiy

    16 days ago

    Good job, we have had a trampoline for 9 years, it was easily the best investment I have made. I have to say though the retaining wall scares me.

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    DanF147

    4 weeks ago on Step 6

    I hope you will remove the rocks or install a safety net. Accidents will happen.
    Better be safe than sorry.

    1 reply
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    CliffsclipsDanF147

    Reply 27 days ago

    Hello Dan, thank you for your concern but we have built a small retaining wall just under the 100cm that trampoline guides give you for positioning it in your garden. At the moment our children are very light so they don't manage to bounce that high, as they get older and more confident we might look into installing a safety net.

    Thank you for reading.

    1556304662374_20190426_195441225.jpg
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    Build-Bot

    4 weeks ago

    Really nice project - and you did a great job documenting it too!

    1 reply
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    huntwa

    4 weeks ago

    Looks really cool! I'm guessing you don't get much rain in your area? Do you have any sort of drainage system in place, or do you just shop-vac it out?

    2 replies
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    Cliffsclipshuntwa

    Reply 4 weeks ago

    Thank you. We get our fair share, but from what i had read as long as you dig a large enough drainage hole it shouldn't ever be a problem (he says with his fingers crossed).

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    huntwaCliffsclips

    Reply 4 weeks ago

    OK I get it, so you're counting on some fast infiltration through the soil at the bottom of the hole. That could work unless there's some heavy rainfall. I bet running and jumping across that trampoline is a blast! It probably launches you twenty feet across the yard at least.

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    allangee

    4 weeks ago

    I've seen one of these first-hand (coworker and neighbor). It slowly filled with water due to soil conditions and the fact that the trampoline itself hindered evaporation. It wasn't uncommon for them to find dead and bloated frogs and mice right under where the kids were bouncing. You'll definitely need to determine how well your soil percolates or, even better, line the bottom and put a small pump at the lowest point. Even a garden pond pump should suffice. Also be aware that if you keep it nice and dry underneath, there are animals that would find that an ideal place to hide out and might be upset once kids start bouncing on their ceiling.

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    jeanniel1

    4 weeks ago

    Wow, this is probably safer than the tramps that are above ground with nets! I guess maybe still need some sort of railing or something to prevent folks from stepping between the springs. Still, what a great idea and a whole heap of work digging! Thanks for sharing

    1 reply
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    Cliffsclipsjeanniel1

    Reply 4 weeks ago

    Thank you, it is good and the green foam mat can be stood on but i would advise jumping on it.

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    funman1

    4 weeks ago

    Where will the water go when it rains?
    That's what's always stopped me from doing this was, that it will fill full of water when it rains like a pool.

    1 reply
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    Cliffsclipsfunman1

    Reply 4 weeks ago

    Hello, from what i understand from reading about other trampolines as long as the drainage hole in the bottom is deep enough it will just drain away like rain water does on your lawn.

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    KingAveGarage

    Question 4 weeks ago

    This is a good idea, especially for yard appeal. But where does rain water go?

    1 answer
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    CliffsclipsKingAveGarage

    Answer 4 weeks ago

    That is good of you to mention it as I forgot to say. In one of the pictures you can see that there is rocks in the bottom. this was an extra hole i dug out and filled with rocks and gravel to give it some where to drain. this is about a foot deep and into the sub soil level.

    I will amend to original instructable to mention this, thanks for the heads up.

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    jessyratfink

    4 weeks ago

    That looks so good! Great that you could use the soil to even out other areas, too :)

    1 reply
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    Cliffsclipsjessyratfink

    Reply 4 weeks ago

    Thank you, It is a good job as I am not sure what I would have done with it all.

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    Cliffsclips

    Tip 4 weeks ago

    This is the front lawn which will filled with some of the top soil from the above project.

    1556121807351_20190424_170728745 - Edited.jpg