The foundation is the part of your shed that nobody sees but everyone depends on. A shed built on a poorly prepared or wrongly chosen foundation will rock, develop racking walls, grow sticking doors, and let in moisture from below — sometimes within its first wet season. Getting the foundation right is also the step most beginners underestimate: it takes more preparation time than any other part of the build, but it makes every step after it easier. This guide covers the five main foundation types for Australian backyard sheds, with practical guidance on which to choose based on your shed size, soil type, and local council requirements.
Foundation Types Compared
| Foundation Type | Approx Cost (AU$, materials) | Permanence | Skill Level | Best For |
|---|---|---|---|---|
| Timber skids only | $100 – $250 | Temporary / Relocatable | Beginner | Small sheds (up to 8×10) on level ground; renters |
| Gravel pad + skids | $300 – $700 | Semi-permanent | Beginner | Most DIY sheds; the go-to recommendation for 8×10 to 12×16 |
| Concrete footings | $400 – $900 | Permanent | Intermediate | Sloping sites; areas with unstable soil; frost-prone elevated areas |
| Concrete slab | $1,500 – $4,500+ | Permanent | Intermediate–Advanced | Workshop sheds; heavy equipment; 12×16 and above |
| Deck blocks (piers) | $150 – $350 | Removable | Beginner | Flat, stable ground; smaller sheds; fast setup |
1. Timber Skids
The simplest shed foundation is two or three treated pine or hardwood bearers (skids) laid directly on prepared ground. No digging, no concrete, no formwork. The floor frame of the shed sits on these skids, which distribute the load across the ground beneath them.
How to Install Timber Skids
- Mark out the shed footprint and excavate 75–100mm of topsoil across the entire area.
- Compact the subgrade with a hand tamper. Add a weed mat barrier to suppress growth under the shed.
- Lay your skids (140×45mm or 150×50mm H3 treated pine) across the width of the shed, spaced evenly. For most sheds, three skids are sufficient: one at each end and one in the centre.
- Level the skids by packing under low spots with hardwood off-cuts or adjustable post stirrups. Check that all skids are level with each other in both directions.
- Build your floor frame across the skids.
Limitations: Direct-to-ground skids on compacted earth can settle unevenly over time, particularly after heavy rain or in clay-rich soils. They work best on flat, stable, free-draining ground. Not appropriate for sheds larger than 10×12 on anything other than ideal ground conditions.
2. Gravel Pad with Skids
This is the recommended foundation for most DIY sheds in Australia. A properly prepared gravel pad provides excellent drainage, resists settling, and gives the skids a stable, level platform that doesn’t shift with seasonal soil movement.
How to Build a Gravel Pad
- Mark an area approximately 300mm larger than your shed footprint in each direction.
- Excavate 150–200mm of topsoil across the full area.
- Compact the subgrade thoroughly with a plate compactor (hire one from a tool hire company for half a day).
- Lay a geotextile weed mat across the excavated area.
- Fill with 150mm of 20mm road base, crushed rock, or drainage gravel. Compact in two layers — 75mm at a time — using the plate compactor. A properly compacted gravel pad should feel completely solid underfoot with zero give.
- Lay your skids on the gravel pad and level as above.
The gravel pad solves the drainage problem inherent in direct-to-ground skids. Water drains through the gravel rather than pooling under the shed floor frame, which dramatically extends the life of your treated timber. For most suburban Australian backyards, this setup will outlast the shed structure built on top of it.
3. Concrete Footings
Concrete footings are poured pads or piers at each corner (and at intermediate points along the wall for larger sheds) that support the floor frame above grade. They’re the right choice for sloping sites where a gravel pad would be difficult to level, or for areas with soft or highly reactive soil.
Standard Footing Specification for Australian Sheds
- Footing size: 300mm × 300mm × 300mm minimum (class N25 concrete)
- Set a galvanised post anchor or stirrup in the wet concrete, aligned to your shed layout string lines
- Allow 24–48 hours for concrete to cure before loading
- Space footings at corners and at maximum 1800mm centres along the wall frame perimeter
Concrete footings are less relevant in most of coastal and low-altitude Australia, where frost heave is not a concern. They’re more valuable on alpine properties (ACT, Victorian high country, Snowy Mountains) and on steep or unstable sloping sites where a gravel pad would require significant cut-and-fill to establish.
4. Concrete Slab
A full concrete slab is the most expensive foundation option but offers the most permanent and functional base for any shed used as a workshop. The slab provides a flat, hard surface for rolling tool chests, parking vehicles inside, and using heavy machinery without vibration transfer through timber flooring.
Standard Slab Specification (Class 10a Shed, Residential)
- Thickness: 100mm minimum
- Reinforcement: F72 mesh or equivalent, lapped 400mm at joins, chairs at 50mm above base
- Concrete: N25 or N32 in reactive clay soil areas
- Edge beams: 300mm × 300mm minimum around the perimeter in reactive soil areas (AS 2870)
- Isolation joint: 10mm foam joint strip at the perimeter against any existing structure
In areas with Class M, H1, or H2 reactive clay soils (common in much of Melbourne, Adelaide, and Brisbane suburban areas), the slab specification should be designed to AS 2870 by an engineer or verified against the standard directly. Using an under-spec slab on reactive clay will result in cracking and movement that undermines the entire shed.
Cost note: A 3.0m × 3.6m slab (10×12 shed) typically costs $1,200–$2,500 for materials and hire only (if you pour yourself) or $2,500–$4,500+ poured by a concretor. Prices vary significantly by location. Always get two or three quotes.
5. Deck Blocks
Precast concrete deck blocks are moulded pier blocks with a slot in the top for seating a 90×45mm or 140×45mm bearer. They sit directly on prepared ground or a gravel pad and support the shed floor frame from below. No digging, no wet concrete — you simply level the ground, place the blocks at the correct positions, and build the floor frame across them.
Deck blocks are faster to install than any other foundation type and are completely removable — useful for temporary sheds, sheds on rental properties, or situations where the shed may need to be relocated. The limitation is that they rely entirely on the ground beneath them being level and stable. On any sloping site or soft ground, use footings or a gravel pad instead.
How to Choose Your Foundation
Use these practical rules to narrow down your choice:
- Small shed (up to 8×10), flat ground, rental property: Gravel pad + skids, or deck blocks
- Medium shed (10×12 to 12×16), suburban backyard: Gravel pad + skids (strongly recommended)
- Large shed (12×16+) used as workshop: Concrete slab
- Sloping site: Concrete footings at varying heights, or a cut-and-fill gravel pad on a moderate slope
- Reactive clay soil: Concrete slab designed to AS 2870
- Bushfire or flood zone: Check with your council — elevated foundations may be required
When in doubt, the gravel pad with timber skids is the right answer for most Australian DIY shed builds. It’s cheap, effective, beginner-friendly, and provides enough drainage and stability for any shed under 15m².
Foundation Regulations
Some council areas specify minimum foundation requirements for Class 10a outbuildings. If your shed requires a building permit, the approved plans will typically specify the foundation type. If you’re building under an exempt development exemption, AS 1684 provides guidance on minimum bearer specifications. Always check with your council if you’re unsure — foundation errors are expensive to fix after the shed is built.
Get the Right Plans for Your Foundation Type
Every shed plan in Ted’s Woodworking includes foundation options matched to the shed size — whether you’re going with skids, footings, or a slab. The plans also include the correct floor frame bearer spacing and sizing for each foundation type, so you’re not guessing at structural dimensions.
Get your complete shed plan with foundation details at Ted’s Woodworking →
