Horticulture Magazine

How To Build A Sunken Trampoline In Your Garden

mother and daughter bouncing on a trampoline

Do you want to give your kids the means to launch themselves high into the air with vigour, but you feel put off by the eyesore of a traditional trampoline?

Do you want to give your kids the means to launch themselves high into the air with vigour, but you feel put off by the eyesore of a traditional trampoline?

If so, you need to learn how to sink a trampoline into the ground.

Building a sunken trampoline in your garden has tons of benefits. It’s fun, it takes up less space, and, most importantly, it’s cheaper and easier than people think.

Why build a sunken trampoline?

Have you ever been to an indoor trampoline park? You’ll see that the space is purpose-built, with trampolines installed flush to the ground. Something like the below:

acrobat jumping on a sunken trampoline
Sunken trampoline, built for purpose

This is no accident. Sinking a trampoline affords tons of benefits and very few drawbacks. In fact, the only reason they’re usually raised in gardens is that the initial setup is more straightforward.

But if you want a trampoline to be a long-term fixture in your garden, sinking it into the ground is a great shout. Here’s why:

Firstly, a sunken trampoline is less conspicuous than its raised brethren. It takes up less vertical space in your garden and makes the overall aesthetic more elegant. 

There’s no need for a safety net, either, as the chance of falling off (or out) of the trampoline is lower.

a normal trampoline with safety walls in the corner of a garden
Fun, but not much to look at

For most people, the main appeal of a sunken trampoline is improved safety. Falling from a raised trampoline can cause serious injuries: Sprains, broken bones, and all sorts. If you fall from a sunken one, though, there’s less distance to the ground and less likelihood of getting a nasty bump.

Creating an in-ground trampoline is cheaper than people expect. Some budget bloggers have achieved their entire in-ground trampoline project for $300. At the time of writing that’s about £230!

If you’re converted, then read on. We’ve written a simple guide for building a sunken trampoline in your garden.

You’ll be pleased to know that no special trampoline is required: Just a regular one and a few steps to make it sit safely in the ground.

Building a sunken trampoline: Step-by-step guide

It is easy, but there’s more to a sunken trampoline than just digging a hole and plopping it right on inside. You’ve got to make sure everything fits correctly, and that things are held in place to make bouncing as safe and fun as possible.

1. Check a few things

Before you do anything, make sure you’ve got permission to dig a large hole in your garden. Call the council to see whether there are pipes below the surface, so you don’t accidentally interrupt the water supply to your home.

Also, decide on the size of the trampoline you’re going to get. This information is required for all future steps.

2. Mark out the area of the trampoline pit

There’s a little preparation to do before you start digging.

Mark out the area with spray paint or chalk. If you measure a length of string equal to the radius of the circle and tie this to a stake at the centre of where you want the trampoline to be, you can easily mark a perfect circle. 

The circumference of the hole should be a few inches larger than that of the trampoline.

3. Dig a hole

This is what your trampoline will sit in.

You have two options here: Dig the hole yourself, or hire a professional to do it.

The trade-off is between price and ease. Hiring a professional will cost more (make sure you get an estimate before they start working), but they will have the experience and equipment to dig a hole quickly. If you dig it yourself, you may be surprised at the amount of manual labour involved.

Make sure to keep the soil you dig up for the time being. This can be used later to fill the hole if it turns out to be too big, and also for shoring up some soil against the trampoline frame to secure it in place.

young boy digging garden soil
If you dig the hole yourself, recruit family and friends to help

When digging the hole, you have to think about letting air escape. Landing on a trampoline forces the air out from underneath, creating a softer landing. Plonking a trampoline in a tightly dug hole without factoring this in can make landings hard and unpleasant.

There are two options here, too. Firstly, you can use pipes to create ventilation shafts out of your hole. Secondly, you can dig a hole slightly less deep than the height of the trampoline, leaving a few inches for air to escape from.

If you go for the latter option, skip the next step.

4. Dig air-escape holes

You can use piping, either flexible or rigid, to let air escape.

By digging tunnels from the wall of the trampoline up to ground level, and inserting piping into them, you create ventilation holes that air can escape through.

Flexible flue will do the trick, as will rigid plumbing pipe. Just make sure it’s at least a couple of inches wide to let air escape quickly enough.

5. Erect the trampoline frame in the hole

In this step, you’re making sure the trampoline fits in the hole as intended. 

If you can comfortably set up the frame with an inch or so of clearance on each side, you’re golden. If not, you will need to widen your hole slightly.

Either way, remove the frame before the next step.

6. Build a retaining wall around your trampoline

It’s essential to ensure the walls of the hole don’t collapse when the trampoline is inside.

Depending on the type of soil in your garden, this step may not be necessary. If you have soft, sandy soil that’s prone to sliding, you should consider a barrier. Don’t be put off by the extra time and effort required at this stage: A retaining wall will save you time and money over the years, and will extend the life of your trampoline.

This can be as simple as screwing two layers of planks of wood around the frame, separated in height by a foot or so. Corrugated metal sheets can be secured on top of these planks to provide a comprehensive barrier strong enough to keep the surrounding wall of dirt from collapsing in.

You can also build a retaining wall in the hole, rather than attached to the trampoline frame. A retaining wall kit will have everything you need, or you can create your own by lining the hole with corrugated metal or some similar material.

7. Lower the trampoline into the hole

With the hole dug and suitably protected against collapse, you’re almost ready to start bouncing.

Lower the trampoline frame into the hole, and use some of the dirt you kept back to pile against the legs. This offers another layer of protection to keep them in place.

8. Test that air can escape

With the trampoline in the hole, it’s time to test the airflow.

Give a couple of test bounces and gauge how soft the landing is. If it’s too hard, check the air is escaping properly. If not, remove the trampoline and add a couple of inches of dirt to the hole to raise it slightly.

9. Bounce!

You’re ready to go! You’ve got a hole, there’s a trampoline in it, and you’ve taken steps to ensure it will stay firmly in place. All that’s left to do now is start bouncing.

a mother and two children using a sunken trampoline
Fun for the whole family

Other sunken trampoline questions

Here are a few trampoline FAQs:

Can’t I just lay the top part of a trampoline across a hole?

Some people are tempted to dig a hole, take the legs off of their regular trampoline, and just lay the top section across the hole. We don’t recommend you do this, for a couple of reasons.

Firstly, it cuts too many corners. Although the process above may seem long-winded, each step is included for a reason. 

Secondly, it’s unsafe. Without a retaining wall or any precautions to strengthen your hole, things are prone to collapse. If your hole collapses while someone is bouncing on the trampoline, all sorts of injuries become possible.

What happens if the trampoline hole fills with water?

Unless you live somewhere prone to monsoons or you’re particularly liberal with hose and sprinkler usage, it’s unlikely the area under your trampoline will flood.

If you’re especially concerned, you can dig a drainage trench underneath. Filling this with gravel will make it easier for the water to escape.

Regardless of the water table where you live, you can use a water pump to drain the hole if you get caught short by an unexpected deluge.

How do you stop bugs and pests from living underneath?

You can cover the gaps with chicken wire to reduce the risk of critters moving underneath. This is recommended if you’ve left a few inches of the trampoline poking above ground for ventilation.

If you’re particularly nervous about bugs getting underneath, a periodic blast of bug spray will make sure you’re bug-free.

What about if leaves get into the hole?

They’ll compost over time, and shouldn’t be a cause for concern.

Enjoy your new-found bouncing

That’s everything! After following the steps in this guide you’ll have a fantastic new sunken trampoline in your garden. Watch as your kids bounce to their heart’s content and, if you’re feeling particularly adventurous, join them!

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