In-Ground Trampoline Cost and Installation: The Pit, the Wall, the Drainage and Who Digs It

The cost lines

1. The kit. Frame, mat, springs, pad; TDU adds the retaining wall, BERG adds the net.
2. Excavation. A 14 ft round is a hole of roughly 14 ft across; by hand it is days, by machine it is an afternoon plus the machine.
3. Spoil removal. The soil from that hole has to go somewhere.
4. The retaining wall, if the kit does not include one.
5. Drainage. Gravel base, a sump or a drain line to daylight, depending on the water table.
6. The net, if the kit does not include one; both TDU and BERG expect one.
7. Surfacing and edging around the rim, so the pit edge is not the hazard.
8. A cover (Capital Play bundles one) so the pit does not fill with leaves.

The pit

The kit maker's instructions give the exact diameter and depth for the frame; the shape is a shallow bowl or a two-tier hole with a shelf for the frame legs, depending on the design. TDU's frame is an in-ground-specific double ring with an extended leg joint, and its instructions are on its site with videos. The depth has to leave room under the mat for the bounce; a mat that bottoms out on soil is the most common DIY failure. Utilities first: call before you dig is not optional on a 14 ft hole.

The retaining wall

Without a wall the sides of the pit slump into it after the first wet winter and the frame ends up leaning. TDU's Classic and North kits include a patented retaining wall system built for the frame, with a lifetime warranty; Capital Play's kits use the same TDU wall design; BERG's dealer page does not describe one. Improvised walls (treated timber, block, corrugated steel) work but have to be sized to the frame and drained; a wall that traps water is worse than none. Kits compared: best in-ground trampoline kits.

Drainage and airflow

Two problems the above-ground owner never meets. Water: a lined hole is a pond, so the base needs gravel and a way out, either a soakaway if the soil drains or a pipe to lower ground. Air: a mat over a sealed pit compresses the air beneath on every jump, which deadens the bounce and pushes air out at the edges; TDU and Capital Play use a patented vented pad and TDU says outright that a trampoline without one is not meant to be in the ground. Vents in the wall or a gap under the pad are the design answers; a solid above-ground pad stuffed into a pit is not.

The net

In-ground does not mean net-free. CPSC's guidance that enclosures help prevent falls does not change at lawn level, and both kit makers agree: TDU pre-drills its top frame for its net system, and BERG will not sell the Champion InGround without one. The pit edge and the retaining wall are the things a child falls onto without a net. The reasoning in full is on in-ground vs above-ground trampoline.

DIY or hired

TDU sells its kits as DIY installations with videos and tips. Realistically: DIY if you can dig or rent a mini-excavator, have somewhere for several cubic yards of spoil, and your soil drains. Hire the dig if the water table is high, the soil is rock or heavy clay, or the site is on a slope. Either way the kit assembly (frame, springs, mat, pad, net) is the easy part; TDU's springs are 104 at 8.5 in, which is an afternoon with the spring tool. An above-ground frame with anchors is the alternative for a renter or a rocky lot: how to anchor a trampoline.

Kits that include the wall

Mistakes to avoid

• Skipping the wall to save money. The sides come in.
• No drainage plan. The pit is a pond by spring.
• An above-ground pad in the pit. TDU's words: not meant to be in the ground.
• No net because it is in the ground. CPSC and both makers disagree.
• Not calling utilities before a 14 ft hole.