Sunken, or in-ground trampoline are a solution for owners who wants to keep a good look for their garden. The choice for such a solution is therefore essentially based on aesthetic reasons.
The frame that you choose for your installation should be of higher quality. The structure being in a confined under ground space will suffer from these harder circumstances. Rust will affect sooner an in-ground trampoline as a standing trampoline. Therefore, creating an in-ground installation with a cheap trampoline is not recommended.
When planning to invest in such an installation, you should consider 6 main subjects that you will have to tackle :
- Air flow
- Water drainage
- Growing plants
- Standard frame or specific solution
- Digging the hole
Air circulation is essential for a trampoline. When rebounding on the mat, the air under the bed is pushed away. With a sunken trampoline, the air-flow must be maintain. If not, then the jumping surface will be hard and you will obtain a « suction effect » which will limit the bounce.
In any case, it’s quite impossible to obtain similar quality of jump in a sunken trampoline as in a standing trampoline. But we can manage to reach similar bounce quality.
One common mistake is to install the frame at ground level. This will prevent any air flow and is highly discouraged. Generally, in such installation the air circulation will push the pad away, consequently leaving springs uncovered and greatly increasing the risks of accidents.
The best solution is to lay the trampoline at least 9 inch above ground, thus allowing a proper air-flow.
Unless your ground is made of sand with natural drainage, creating an evacuation system at the bottom of the hole will be essential. Installing drainage pipes and a drainage system that is adapted to your garden soil will prevent water to stagnate.
We strongly advise you to ask for professional help if you are not familiar with such a work.
Plants growing :
Plants might grow in the pit. Laying a geotextile canvas on the bottom of the hole prevents that from happening and also helps the dirt to stay put.
The level of security provided by an in-ground trampoline is similar to a standing trampoline with enclosure. The sunken trampoline is 9 to 12 inches from the ground, thus limiting the height of the fall. Furthermore, as the frame is not at ground level, children will not accidentally run or bike onto the mat while somebody jumps on it.
The best security level will be of course provided by a sunken trampoline with an enclosure. This type of installation can be harder to build unless you find distinct product.
Standard frame or specific solution :
You can use a normal standing trampoline and sunken it. Simply, the amount of dirt you have to move will be greater than if you use a specific solution. For a standard frame, the hole will have to be in the shape of a cylinder.
Etan international offers since 2015 a special frame that is especially designed for in-ground trampoline. This product comes with a low reinforced frame, strong padding and a specially designed skirt. The quality of the frame and the padding guaranty a longer life-expectancy and the skirt maintains a good air-flow. With this solution, the hole only requires to be in the shape of a semi-circle.
The following video presents the installation with a special frame.
If you use a standard standing frame, then you must dig a cylinder which is equal to :
- the diameter of your frame plus 1 inch
- the height of your frame minus 9 to 12 inches (depending on how high you want the mat to be from the ground.
Then, screw our in-ground kit to the side of the structure to maintain the cylinder shape and allow proper air flow.
If you chose a specific in-ground trampoline, then you must dig a semi-circle with the following depth on the centre (depending on the trampoline size) and then follow the steps shown in the video above :