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How to Install a Sunken Trampoline

Everyone loves sunken trampolines (also known as in-ground, ground level or even pit trampolines) for many good reasons. There has always however been a resistance to installing a sunken trampoline due to issues such as cost, drainage, soil removal and so on.

It is however not as difficult as you may think to install a sunken trampoline, and I'm going to explain all the options you have and make it easy for you to obtain a perfect in-ground trampoline solution.

Sunken trampoline advantages

Here's a recap on some of the reasons why in-ground trampolines are becoming so popular:

  • Sunken trampolines look great, they're not so high off the ground and have no unsightly safety net.
  • They're generally safer with no fear of smaller children falling off the ladder or out of the door of the safety net. It makes parents lives easier without having to supervise younger children or assist them climbing up into a trampoline.
  • There's no possibility of high winds launching your trampoline into your next door neighbour's garden!
  • Sunken trampoline's are less costly to maintain if you don't have a net which is an expensive item to replace.
  • This type of trampoline allows your children to have more fun and play a variety of different games as there's no net to interfere with and no ladder to climb.
  • Parents can enjoy using the trampoline more as there's no need to climb up a ladder and through a small opening onto the trampoline.

Is my garden suitable?

This is your first consideration. You'll need to make sure you don't have a high water table or you're prone to flooding. If in any doubt, dig a trial hole (about 3ft deep) in the area where you want to sink your trampoline and leave for 24 hours to see if the hole fills up with water.

You will need at least 2 metres around the trampoline as a safety run off and even then make sure there are no hazards such as brick edges or concrete posts which could cause injury.

Finally try and ensure there are no utility services such as gas or water pipes in the area where you're going to dig. This can be an expensive oversight!

Trampolines Down Under Retaining Wall

Trampolines Down Under Retaining Wall

What trampoline?

The first thing you'll need to consider is what size and shape trampoline you want.

What works best in the space you have? Round, square or even oval. Do you have an existing trampoline you want digging in?

If you have an existing trampoline you want digging in then you will need to use a retaining wall to stop the earth falling in under the trampoline.

You can use a wooden construction, concrete breeze block or better still a purpose made retaining wall as offered by Trampolines Down Under.

Capital In-ground Trampoline

Capital In-ground Trampoline 

Using a traditional trampoline and full-height retaining wall will mean you'll have to excavate a lot of soil and the cost of the retaining wall is expensive.

A better option is to purchase a purpose-built in-ground trampoline such as the Capital In-ground Trampoline Kit.

The design of this solution means less soil disposal and the cost of the trampoline and retaining wall is also reduced.

Digging the hole

Firstly you'll need to determine the size and depth of the hole you want to dig. If you're using a full height wall and say a 12ft round trampoline, you need to dig a 14ft circumference hole to a depth of about 3ft. Once the trampoline and wall are in place, you then fill in on the outside and inside of the wall.

Capital In-ground Trampoline

Capital In-ground Trampoline Hole Diagram

If you are using a Capital In-ground Trampoline Kit, then there is less soil to dig out. The profile of the hole is pictured on the left here.

You have the option to either hand-dig the hole or use a mini-digger. On a smaller trampoline say a 10ft, provided your soil is not too hard, then it's fairly straightforward to dig by hand. It will take two people a full day and make a great work-out!

If however you have a larger hole to dig, say 14ft, then a mini-digger will greatly assist digging out most of the soil, whilst you can finish by hand.

Whether hand-digging or using a mini-digger you will still have the issue of soil disposal. You will need to hire a skip or better still use a grab lorry to remove the soil.

To save money, you could consider creating a feature in your garden with the excess soil - this could be a bank (for kids to play on) or raised flower-beds.

What about drainage?

Whether you need drainage will depend of the type of soil you have. If you have sandy soil, you probably won't require any further drainage. If however you have non-porous soil which has a high clay content, then it's wise to at least put in a soak-away or similar at the bottom of the hole.

In more extreme cases a drainage channel may have to be dug out to a lower lying area in your garden.

Putting a cover on the trampoline will also help prevent excess water getting into your hole.

Will air get trapped under the trampoline?

Trampolines Down Under vented Trampoline Pads

Trampolines Down Under Vented Trampoline Pads

The simple answer is ... yes. This is a real problem for in-ground trampolines. The quality of the bounce will be affected if there's nowhere for the trapped air to escape as you bounce on the trampoline. This is especially true for older or heavier children.

You'll also experience the high irritating 'pad slap' noise as the trapped air pushes up the pads and they slap down on the jump mat.

One solution is to put in vents through the retaining wall and out into your garden somewhere. But far better is to used vented pads, these are really tough pads that have been specifically designed for use on sunken trampolines. They are made by US company Trampolines Down Under and are patented.

Please share your comments and experiences on this blog post - installing a sunken trampoline is great fun and a very fulfilling. Your children will get hours of endless fun on UK's no 1 piece of children's play equipment.