You may already have a perfectly useful base for a plastic garden storage box. A sound patio can save you building something new, provided the actual spot supports the whole unit and doesn’t leave it rocking or twisting.
When I’ve assembled stores such as the Keter Midi, a steady base has made fitting the light panels and lining up the doors much easier. Before spending money on more paving, check what your existing surface is doing, especially after rain.
I’ll show you how to check the support, drainage and working space. A plastic floor is part of the box; it cannot correct a soft or uneven surface underneath.
Floor, base and foundation: what is the difference?
The floor is the panel inside the storage unit. The base is the surface underneath it. A foundation usually means prepared support built into the ground. Retailers do not always use these words consistently, so look beyond a single feature label.
Keter’s brown Midi 273840 page lists both “Foundation Required: No” and a minimum foundation size of 132 × 71.5cm. That does not establish that any patch of grass is suitable. Use the exact model’s manual to decide what support it needs; do not assume you must build a concrete slab just because the word base appears.
Can a garden storage box sit on an existing patio?
I have set up the Keter Store It Out Midi and Pro on level surfaces. With the Midi, the panels felt light until the unit was assembled; keeping the base flat helped the doors and lid meet properly, and I avoid leaning very heavy equipment against its walls. The Pro gave me more accessible room, though the larger panels were easier to align with help. If your patio is sound and level, I would spend first on a storage size that fits your tools and leaves room for the doors, rather than adding a new base without a reason.
Mark out the full footprint, not just four corners. Walk over the slabs and inspect the joints and edges. Slabs that rock when you stand on them, settled corners and hollows deserve attention before you put a loaded box there. A spirit level and straight edge help you see the surface clearly; check in both directions and across different parts of the footprint.
A patio may have a deliberate drainage fall. That does not automatically make it suitable or unsuitable: check the unit’s installation requirements and make sure it will sit without rocking or twisting. Do not force doors into alignment by loading the box or tightening fixings harder.
Check the space in front as well: the doors need to open and a mower may need room to turn out. Preparing a neat base in an awkward position is frustrating. Look at the site after rain. If water gathers where the box will stand, deal with the cause before filling it. Keter advises a flat, well-drained surface in its bin-storage guidance. Avoid creating a raised lip that traps water around the unit.
Can you put plastic storage directly on grass?
I would start by finding a more dependable surface. Grass hides hollows, soil can soften after rain, and the space underneath becomes difficult to maintain once the box is full. Plan the position properly rather than rely on the enclosure’s weather-resistant description.
A prepared gravel area and a few stones scattered over soil are different arrangements. Check whether your model allows that surface and how its floor must be supported. Individual bricks under corners are not a substitute for specified support across the base.
How much space do the Midi and Pro need?
Mark the external width and depth, then add the access required by the manual and your equipment. These manufacturer examples refer to Midi 17210427 and Pro 256624. They are not confirmation of the dimensions of every retailer variant.
| Storage unit | External width × depth | Calculated footprint |
|---|---|---|
| Manufacturer Midi 17210427 | 132 × 71.5cm | About 0.94m² |
| Midi Amazon listing checked | 130 × 74cm | About 0.96m² |
| Manufacturer Pro 256624 | 145.5 × 82cm | About 1.19m² |
Area is a calculation, not the complete site requirement. A narrow space can have enough square metres yet the wrong shape. Allow for doors to swing, the lid to lift, assembly and a mower to enter without striking a bed or wall. For internal fit, see our Midi vs Pro mower-storage comparison, then confirm the version supplied.
Five checks before ordering
- Exact model: compare the retailer’s version with its manual.
- Support: inspect the full footprint, including joints and edges.
- Water: check where rainwater gathers and how it escapes.
- Access: measure the lid, doors and equipment route.
- Complete cost: include required surface preparation and model-specific fixings.
The smaller Midi only saves space if your equipment fits. Include any work needed to create a usable position in the buying decision. Check delivered cost for the exact variant; a low headline price does not settle the complete cost.
Do I need to anchor the storage unit?
Follow the exact manual’s anchoring and wind guidance. Do not improvise by drilling panels, weighting a lid or adding unapproved fixings. Anchor types and structural base construction depend on the unit and site.
For other formats, see our lawn mower and tool storage guide or our garden storage box guide. Choose the storage and its position together before ordering.
Check the Keter Midi listing on Amazon and confirm its supplied dimensions and instructions.
Sources checked 18 September 2026: Keter Midi 17210427 specifications, Pro 256624 specifications, brown Midi installation fields and Keter bin-storage siting guidance.
