Shed and equipment pads are usually reinforced slabs over a compacted granular base. Garages and additions generally need footings below frost depth or a frost-protected design, plus permits and inspections under the Minnesota State Building Code. Contractors doing more than one special skill must be licensed by DLI. Notify Gopher State One Call before digging.
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Sheds, detached garages, workshops, three-season porches, hot tubs and home additions all need something solid to sit on. In Minneapolis and St. Paul, where many older homes have detached garages off an alley and suburban lots keep adding sheds and porches, slab and footing work is a steady part of concrete contracting. In Minnesota, the big question for anything structural is frost: footings generally have to reach below the depth where the ground freezes.
Common slab and foundation projects
- Pads for storage sheds, playhouses and garden buildings
- Slabs for detached garages and workshops, including replacing an old alley garage slab
- Pads for hot tubs, generators and air conditioning equipment
- Footings and slabs for additions, three-season porches and sunrooms
Sheds and pads
A shed or equipment pad is usually a reinforced slab over a compacted granular base, sometimes with a thickened edge. Size the pad to the building plus a little extra, keep it level for the structure but able to shed water at the edges, and confirm it meets setbacks from property lines, easements and the alley. Many Twin Cities cities require a permit for accessory buildings above a certain size, and HOAs often have their own rules. Check before you pour.
Garages and frost
A detached garage generally needs more than a simple slab. Depending on your city and the building's design, that can mean frost footings that extend below frost depth or an engineered frost-protected design. Minnesota's statewide building code sets frost depth by zone, and the counties around the Twin Cities have long been in the zone with a 3.5-foot minimum footing depth. The state has reviewed those zones, so confirm the current requirement with your city's building department. Ask about vapor retarders, insulation and conduit before the pour if you plan to heat or wire the space.
Additions and structural work
Foundations for additions and living space carry the structure and must meet the Minnesota State Building Code as administered by your city. That typically means a permit, footings sized for the soil and load, inspections before concrete is placed, and sometimes engineered drawings. In Minnesota, a contractor who works directly for a homeowner in more than one special skill area, such as concrete plus framing, must hold a residential building contractor or remodeler license from the Department of Labor and Industry. A contractor doing only concrete work, which DLI lists as including slabs and poured-in-place footings, generally doesn't need that state license. On additions, the concrete crew often works under a licensed builder who holds the permit, so make sure everyone's role is clear.
Twin Cities site factors
- Glacial soils: footings should bear on firm, undisturbed soil. Soft clay, organic soil or loose fill may need to be removed or the design adjusted.
- Groundwater and drainage: keep the slab above surrounding grade and slope the ground away so water doesn't collect and freeze against the new structure.
- Slopes and bluffs: lots along the Mississippi and Minnesota river valleys can have steep slopes where cities apply extra review.
- Utilities: Minnesota law requires notifying Gopher State One Call at least 48 hours before digging, not counting weekends and holidays. Private lines to garages or sheds aren't marked, so locate those separately.
Questions to ask
- Does this project need a permit, and who will pull it?
- What footing depth or frost protection does the design use?
- How thick is the slab, and what reinforcement and base are included?
- Are you licensed with DLI if the job includes more than concrete?
Planning a building or addition? Request a slab or foundation contractor and include the structure's size and use.
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Frequently asked questions
How deep do footings need to be in the Twin Cities?
Minnesota's building code sets minimum footing depth by frost zone, and the Twin Cities counties have long been in the 3.5-foot zone. The state has reviewed those zones, so confirm the current requirement with your city's building department.
Does a concrete contractor need a license in Minnesota?
A contractor who works directly for a homeowner in more than one special skill area must have a residential building contractor or remodeler license from DLI. A contractor doing only concrete work generally doesn't, though cities can require their own licenses for work in the right-of-way.
Do I need a permit for a shed slab?
Many Twin Cities cities require permits for accessory buildings above a certain size, and some for the slab itself. Setbacks, alley rules and HOA rules also apply, so check with your city first.
Sources and further reading
- American Concrete Institute (ACI)
- Portland Cement Association (PCA)
- Minnesota Department of Labor and Industry: residential contractor licensing
- City of Minneapolis: curb cuts for residential properties
- City of Minneapolis: city sidewalk repair process
- City of Saint Paul Public Works: sidewalks
- City of Saint Paul: sidewalk contractor license
- City of Bloomington: residential driveway approaches and curb cuts handout
- Minnesota Rules chapter 1303 (frost depth zones), Office of the Revisor of Statutes
- Hennepin County landslide atlas: Minnesota River valley
- Minnesota Pollution Control Agency (winter salt and chloride)
- Gopher State One Call (Minnesota 811)
- Minnesota Department of Public Safety: Gopher State One Call