Sheds sit on one of three foundations: a compacted gravel pad (or skids), concrete footings dug down toward frost, or a poured concrete slab. The right pick comes down to the shed's size, weight, and whether it needs a permanent base. Here are the three shed foundation choices we build, and when each one fits.
The three shed foundations at a glance
Every shed needs a flat, stable, well-drained base. Get that wrong and the building racks, the doors stop closing, and the floor rots out from below. Get it right and the shed sits true for decades. Which base you need is mostly a question of size and weight. Here is the short version before we dig into each one.
| Foundation | Best for | Goes toward frost? |
|---|---|---|
| Gravel pad or skids | Small, lighter storage sheds | No, it floats on a draining granular bed |
| Concrete footings | Larger or permanent sheds | Yes, dug down toward frost |
| Concrete slab | Heavy sheds, shop or workshop use | Thickened or footed where needed |
Gravel pad or skids: the best base for a small shed
For a small storage shed, a compacted granular pad or a set of skids is usually all you need. We strip the topsoil, lay and compact clear granular stone in lifts, and level it flat. The shed then sits either straight on that pad or on pressure-treated skids (runners) set on the gravel. Because the stone drains, water moves through it instead of pooling under the floor.
This is a floating foundation. It does not go down to frost. With a draining gravel bed and a light load, a small shed can ride the seasonal ground movement without racking. The work that makes or breaks it is the prep: strip the organics, compact in layers, and keep the pad a little bigger than the shed footprint so the edges do not slough off. A pad thrown on soft topsoil is the most common reason a cheap shed ends up crooked within a year.
Footings dug toward frost
A larger shed, or any shed you want on a real, permanent foundation, should sit on footings dug down toward the frost line. In the Hamilton and Halton area that working depth is about 1.2 m (4 ft) below grade. The footings bear on undisturbed soil below frost, so the building cannot be lifted when the ground freezes.
This matters here because of freeze-thaw. Southern Ontario soil takes on water, freezes and pushes up, then drops back down when it thaws. Heavy clay, common on the Hamilton Mountain and around Ancaster, holds water and heaves hard. A shallow base under a big shed gets shoved up one corner at a time until the frame is racked and the doors bind. Footings to depth take that movement off the table. We use them when the shed is large, heavy, or going on a sloped or clay-bound lot near the escarpment.
A poured concrete slab
A concrete slab gives you a hard, level floor in a single pour, which is why it is the go-to for a heavier shed, a workshop, or anything you want to roll a mower or equipment in and out of. We excavate, lay and compact a granular base, form the edges, and pour. The slab is the floor and the foundation at once.
The mix is the same air-entrained, exterior-grade concrete we use for our outdoor flatwork. Air-entrained concrete is built to survive Ontario freeze-thaw and road salt without spalling, so the slab holds up to winter instead of flaking apart at the surface. On frost-prone ground, or for a bigger structure, we thicken the slab edges or tie them into footings so the slab behaves as a proper foundation rather than a patio that happens to have a shed on it.
Which shed base is right for you?
The honest answer in the gravel pad vs slab shed question is that it depends on size, weight, and how permanent you want the building to be. A few rules of thumb we work from:
- Small, light storage shed: a compacted gravel pad or skids is the best shed base. Simple, drains well, and the least to build.
- Larger or permanent shed: footings dug down toward frost, so the building never heaves.
- Heavy shed, shop, or workshop floor: a poured slab, thickened or footed where it needs to be.
- Soft, clay, or sloped lot: lean toward footings or a footed slab no matter the size, because that ground moves the most.
When we quote a shed foundation in Ontario we look at the footprint, what is going inside, and the soil on your lot before we call the base. The cheapest base that will actually hold the shed level is the right one.
Permits, zoning, and locates in Ontario
The base is not the only thing to get right. The rules below are provincial, so they hold across Hamilton and the surrounding towns.
- Building permit: under the Ontario Building Code, a detached one-storey shed of 15 m² (about 160 sq ft) or smaller, used for storage with no plumbing, does not need a building permit. Go over 15 m², or add plumbing, and a permit is required.
- Power: running electrical service out to the shed needs an ESA (Electrical Safety Authority) permit, separate from any building permit.
- Zoning: setbacks from the property lines, maximum height, and lot coverage still apply at any size. These vary by municipality, so we set the shed back off the lines and under the height cap, and confirm the details with the city before building.
- Locates: before we dig the pad or the footings, we book locates through Ontario Dig Authority. It is free, and in Ontario it is the law, whether you are digging one post hole or a full set of footings.
Frequently Asked Questions
Do I need a permit to build a shed in Ontario?
Under the Ontario Building Code, a detached one-storey shed of 15 m² (about 160 sq ft) or smaller, used for storage with no plumbing, does not need a building permit. Anything larger, or with plumbing, does. Running power to it needs an ESA permit, and zoning setbacks always apply.
What is the best base for a shed?
It depends on the shed. For a small, light storage shed, a compacted gravel pad or skids is the best base, because it drains well and is simple to build. For a larger or permanent shed, footings dug toward frost or a poured concrete slab keep a heavier building level for the long haul.
Does a shed foundation need to go below the frost line?
Not always. A small shed on a draining gravel pad can float and ride the seasonal movement. A larger or permanent shed should sit on footings down toward frost, about 1.2 m (4 ft) in this part of southern Ontario, so freeze-thaw cannot heave it and rack the frame over a winter or two.
Building a shed this season? Let's get the base right
A shed only lasts as long as what it sits on. The Hammer Construction builds sheds across Hamilton and the surrounding towns on the right foundation for the size, whether that is a gravel pad, frost footings, or a slab, with the locates booked before we dig. Licensed and insured. Get a free quote at our online estimator, call or text (647) 424-1148, or email hello@thehammer.construction