Why Would You Install a Trampoline "In Ground"?
Some people have a preference to have their trampoline installed at ground level, here are some of their reasons:
- it simply looks good
- they have easy access to the trampoline
- it can fit in with their backyard landscape design
- there are less obstructions in their backyard to spoil their view
- the wind has a lot less chance to take the trampoline on an unplanned outing
- there is a perceived increase in safety as less distance to fall and trampoline can't tip over
How is it done?
There are quite a lot of blogs and articles about how to build your own in ground trampoline. Having not built one in ourselves we don't feel qualified to say any more on the topic other than what many of our customers have fed back to us what they have done.
Here are some techniques used:
- Frame mounted on top of a retaining wall
- Retaining wall built around an above ground trampoline
- Complete trampoline installed into a hole in the ground
Frame Mounted on Top of a Retaining Wall
Customers have dug a hole, provided some form of drainage, built a retaining wall the size of the trampoline frame and then secured the frame onto the retaining wall.
- The height of trampoline is stable (less likely to sink), simple layout as has least amount of trampoline parts required.
- Retaining wall needs to be stronger than the original frame as it will now be taking all the stress, more thought required to provide an air flow system from under the trampoline.
In ground rectangle trampoline in Melbourne
- Hole prepared with retaining wall,
- Not visible is the drainage system and remember to allow for air flow from under the trampoline
- Mat secured by springs and frame pads secured in place.
Retaining Wall H Section Post
Another good way for the retaining wall vertical posts is to use "H" Galvanised Steel into a post hole then set with concrete.
Retaining wall built around an above Ground Trampoline
Customer made a retaining wall above the ground and put the trampoline inside the retaining wall, then bought a couple of loads of dirt and pushed it all up to the retaining wall and essentially made a hill in his back yard with the trampoline in the middle.
- easier to setup a drainage system,
- might be easier to revert backyard to original condition,
- Trampoline can easily revert to above ground style, you could possibly design it so net could still be used
- still need to move a lot of dirt,
- still need to build a strong retaining wall
Complete Trampoline Installed into a Hole in the Ground
Customers have dug a hole and then simply placed the trampoline with its legs into the hole. This is the kit we provide.
- simplest construction and assembly,
- can revert trampoline to above ground style
- keeps trampoline and retaining wall forces separated
- trampoline looks after all the jumping forces
- retaining wall looks after all the soil related forces
- trampoline frame is still free to flex as designed enabling longer life of components
- trampoline can be removed for any maintenance of the pit, retaining wall or trampoline
If we are asked to suggest a preferred method then for these reasons this is our choice.
- need to counter the tendency for the trampoline legs to sink into the dirt over time (needs stable base)
For this above installation this is the materials list used and time taken to install:
- 4 days of hand digging and wheelbarrowing
- 1 and a 1/2 days of retainer wall construction and grass replacement
- 30 treated pine sleepers 200mm by 75mm by 3 meters
- 2 treated pine posts 100mm by 100mm by 3 meters
- 1 large box of 100mm gal flat head nails
- 1 tennis ball
- 7m by 5m of weed matting
- Kids love it.
Tips and considerations
*** Please contact your local council to enquire if a permit is required in your area.
The hole and retaining walls need to be prepared with the following in mind:
- The base needs to be firm enough to prevent the trampoline slowly sinking over time
- Like any hole in the ground it can become a receptacle to hold water, you will need to provide adequate drainage either by utilising gravity (e.g. compacted screenings with drainage pipes) or via a dedicated drainage pit with sump pump
- The base soil content can vary a lot, some soils are relatively inert however some can attack the galvanised coating and steel so its advisable to keep any trampoline steel framework insulated from the base soil, this can be done with compacted screenings.
- Design and construction of the retaining wall is crucial for long term hassle free enjoyment, it can be surprising just how much pressure the soil can put against a retaining wall
- The depth of the hole needs to be adequate to provide any user sufficient clearance during a high load bounce, a safe rule of thumb is to allow the same depth as the equivalent above ground trampoline has in height off the ground
- Air flow under the trampoline definitely needs to be considered, when a trampoline is above the ground it’s not really noticeable how much air is actually pushed down and outwards because the framework is very open to the atmosphere, however when the trampoline is sealed off level with the ground with padding over the springs the bounce is noticeably deadened and will disappoint the user.
There are several methods you can use to overcome restricted airflow when installing an in-ground trampoline:
- you can have the top of the frame raised above ground level a little bit, depending on trampoline size, approximately 50 - 100mm air gap is required
- you could provide a system of air vents from under the trampoline to the atmosphere by drainage pipes or ducting
- you could just remove the spring pads but this takes away a mandated safety feature, so this is not recommended
The trampoline frame sizes listed on our website are for naming the generic size of a trampoline and should be treated as a ballpark reference only, these nominal sizes should not be relied upon when digging the actual hole or for making the retaining wall. For our rectangle range, the long side rail bows out a little by design which needs to be factored in. Depending on installation method you choose, you may also need to allow for an airflow gap. When sizing up to make the hole or retaining wall, it is strongly suggested you already have the trampoline with the mat and springs assembled so you can then directly measure off the "actual" assembled product dimensions.
We love to see how our customers have gone about installing their trampoline, the pitfalls they have come across and any other constructive tips we can share with others. We welcome your results, stories, photos and videos, please send them to us.