Garage & Shed Slabs in Eden Prairie, MN

Garage and shed slabs are the floors and foundations for detached garages, storage sheds, workshops and similar outbuildings. Unlike a patio, a slab for a building has to be square, level and sized exactly to the structure, with edges strong enough to carry the walls. When a slab is off by an inch, the builder fights it for the whole project.

Frost and the slab-on-grade rule

Minnesota's building code sets minimum footing depths for frost protection: 5 feet in the northern Zone I counties and 3.5 feet in Zone II, which includes Hennepin County. The same rule (Minn. R. 1303.1600) allows slab-on-grade construction, without frost footings, for detached one-story private garages, carports and sheds no larger than 1,000 square feet, on any soil except peat or muck. That is why most detached garages and sheds here sit on a floating slab with thickened edges instead of deep frost footings. Larger buildings, or buildings attached to the house, are a different design, and we work from the plans your builder or the city requires.

What goes into a building slab

Layout. We work from the building's dimensions and the planned door locations, and square the forms corner to corner.

Excavation and base. Topsoil and soft soil come out. A compacted gravel base goes in to the planned depth. Any soft spot under a building slab shows up later as a crack through the floor.

Thickened edges. The perimeter is dug deeper and poured thicker than the field of the slab, so the walls bear on more concrete.

Reinforcement. Rebar around the perimeter and through the field, set on supports. Anchor bolts for the sill plate are set in the fresh concrete where the building plan calls for them.

Vapor barrier. Under a slab for a heated shop or storage that needs to stay dry, a plastic vapor barrier limits moisture coming up from the ground.

Surface and pitch. A garage floor is pitched gently toward the door so snowmelt off the car runs outside. Shed floors are usually flat. A steel-troweled finish suits a workshop, and a light broom texture adds grip.

Before we pour

Eden Prairie's planning guidance notes that accessory structures have setbacks from lot lines based on the zoning district, and the city provides an accessory structure worksheet. We check with the city whether your building needs a permit, confirm the building location, size and setbacks with you, and pour to the approved plan. Before any digging, we file a Gopher State One Call locate request.

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Common slab jobs

• New slab for a detached garage built by you or a builder
• Shed pads for prefab or site-built sheds
• Workshop slabs with a smooth finish
• Replacing a cracked, sunken floor in an old detached garage
• Pads for generators, air conditioners and trash enclosures

Replacing an old garage floor

Detached garages built in the city's early decades often have floors that have broken into pieces or dipped toward the center. If the walls and framing are sound, the old floor can usually be broken out and repoured inside the building on a new base, with fresh rebar and a fresh slope to the door. It goes slower than an open-air pour because the concrete is wheeled in, but the garage stays standing.

Caring for a garage slab

Seal the floor so salt slush off your car does not soak in. Sweep or squeegee meltwater out during winter. Keep gutters and downspouts directing water away from the slab edges.