Shed and equipment pads are usually reinforced slabs over a compacted base, while workshops, casitas and additions need thicker slabs and footings designed for Valley soils, with permits and inspections. Check easements, setbacks and HOA rules, confirm the contractor's Arizona ROC license, and contact Arizona 811 before digging.
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Sheds, workshops, detached garages, casitas, ramadas, hot tubs and room additions all need a solid base. A small storage shed may only need a simple pad. Anything that becomes living space, or is attached to the house, needs footings and a foundation that meet the building code your city has adopted, with permits and inspections.
Common slab and foundation projects
- Pads for storage sheds and garden buildings
- Slabs for workshops, detached garages and RV covers
- Foundations for casitas, guest houses and accessory dwelling units
- Pads for hot tubs, pool equipment, AC condensers and generators
- Footings and slabs for room additions and enclosed patios
Small structures and pads
A shed or equipment pad is usually a reinforced slab over compacted soil and aggregate base, often with a thickened edge. Size it to the structure plus a little extra and keep it a bit above the surrounding grade. Check setbacks from property lines and walls, and look at your plat for public utility easements, which are common along the back and sides of Valley lots. Many cities require permits for accessory structures above a certain size, and HOAs often limit shed height and placement so they don't show over the wall.
Workshops, garages and casitas
Slabs that will carry vehicles, heavy tools or living space need more thickness and reinforcement, plus footings to carry the walls. Plumbing, electrical conduit and a vapor retarder all have to be planned before the pour. Casitas and guest houses are popular in the Valley, and they usually go through full building plan review.
Additions and structural work
Foundations for additions and other habitable spaces have to be designed for the soil and the load and inspected before concrete is placed. The Arizona Registrar of Contractors licenses contractors in the state, and concrete work is its own residential classification. Structural work on a home generally means a licensed contractor holding a building permit, often a general contractor with a licensed concrete subcontractor. Make sure everyone's role and license is clear.
Phoenix-area soil and site factors
- Caliche: hard cemented layers can make digging footings slow, and they can trap water. Contractors may need heavier equipment, and drainage around the slab still matters.
- Expansive and collapsible soils: some Valley soils change volume with moisture. On larger structures, ask whether a soils report is needed; your city's building department can tell you what it requires.
- Retention and grading: many lots are graded to hold or direct stormwater. A new slab shouldn't fill a retention area or send water toward the house.
- Utilities: Arizona law requires contacting Arizona 811 at least two working days before digging so underground lines can be marked.
Questions to ask
- Does this need a permit, and who will pull it?
- What thickness, reinforcement and base are included?
- Are engineered drawings or a soils report needed?
- Which Arizona ROC license do you hold for this scope?
Planning a shed, casita or addition in the Phoenix metro? Request a slab or foundation contractor and include the structure's size and use.
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Frequently asked questions
Do I need a permit for a shed slab?
Many Valley cities require permits for accessory structures above a certain size, and some for the slab itself. Setbacks, easements and HOA rules also apply. Check with your city's building department before pouring.
Does a concrete contractor need a license in Arizona?
Generally yes. The Arizona Registrar of Contractors licenses contractors, and concrete has its own classification. Arizona's handyman exemption only covers minor work under $1,000 in total that doesn't need a building permit. Look up any contractor's license on the ROC website.
Is caliche a problem for a slab?
Caliche can be hard to dig through, which affects excavation cost and footing work, and it can keep water from draining. It isn't necessarily bad support, but drainage around the slab and proper base preparation still matter.
Sources and further reading
- American Concrete Institute (ACI)
- Portland Cement Association (PCA)
- University of Arizona Cooperative Extension: Managing Caliche in the Home Yard (AZ1281)
- ASCE study: residential foundations and expansive clay in the Phoenix Valley
- Arizona Registrar of Contractors (ROC)
- Arizona Revised Statutes 32-1121 (contractor license exemptions)
- Arizona Administrative Code R4-9-103: residential license classifications
- City of Phoenix: Driveway Policy for Single Family Development
- City of Phoenix Street Transportation: special permits
- City of Scottsdale: Environmentally Sensitive Lands Ordinance
- SRP: residential irrigation basics
- Arizona 811: call before you dig