Before
You Buy

Concrete Slab — Full Specs

• Anchors: 1/2" concrete wedge / expansion anchors, commonly 1/2"×5.5", ×6", or ×7". Minimum embedment 3.75"–5". Torqued 45–65 ft-lbs. Kept ≥2.5" from the slab edge to prevent edge breakout. Cracked or edge-critical concrete uses epoxy/adhesive anchors rated for cracked concrete.
• Thickness: minimum 4" for carports and light-duty garages; 6" for commercial shops, agricultural buildings, and habitable structures; up to 8" for the heaviest equipment.
• Strength: ~3,000 PSI light use; 3,500 PSI residential garage; 3,500–4,000 PSI commercial, agricultural, and habitable. IBC minimum ground-supported slab is 3.5".
• Reinforcement: #3 rebar (⅜") grid at 18" on-center both directions, with #4 (½") in thickened edges and footings. Welded wire mesh (6×6 W1.4) for light use only, set in the upper third of the slab. MBMA calls for continuous perimeter rebar, minimum two #4 bars up to 30 ft wide. Fiber is crack control only — not a rebar substitute.
• Sub-base: compacted gravel beneath the slab for drainage and stability.
• Slab size: three styles — Edge Offset (outer dims +5" all around), Notched Edge Offset (slightly less), Edge Flush (equals outer dims). All footers ≥4" thick and ≥12" wide.
• Edge lip: leave ≥3" of slab around the building, or use L-brackets, to prevent edge chipping and anchor blowout.
• Cure: minimum 28 days before install day.

Foundation Types for Larger Buildings

• Monolithic slab (thickened edge): single pour combining slab and perimeter grade-beam footing (~12"×12"). Fastest and most affordable — ideal for warm climates and regions with a shallow frost line.
• Slab + perimeter stem walls: footings poured below the frost line. Preferred for barndominiums so plumbing can be run before the pour.
• Continuous grade beams / strip footings: for medium-to-large structures.
• Pier-and-beam (isolated footings): drilled piers at each column — for poor soil, heavy interior loads, or agricultural barns without a finished floor.
• Footing sizing: 12"×12" standard residential; 24"×24" minimum for 32 ft+ wide (some specs 30"×26" for double/ladder-leg); permitted builds require engineer-stamped footings ≥24"×24".

Gravel Pad — Full Specs

• Dual anchor system: mobile-home / helical auger anchors 30–36" deep at corners and alternating legs (resist uplift), plus 18–36" rebar pins between them (resist lateral shift). Augers thru-bolted with 3/4" bolts. Never rebar alone on a certified build.
• Depth: 4–6" of compacted crusher run / road base (has fines) — not smooth round rock, which shifts and never locks in.
• Extend the pad at least 2 feet beyond the building on every side so the base rail never sits on a crumbling edge.
• Compaction: spread and compact in thin lifts, a few inches at a time; level the underlying dirt first.
• Soft soil: lay geotextile fabric under the gravel over clay or mud so rock does not sink over time.
• Maintenance: gravel can trench and shift over time — it is re-levelable.

Dirt / Bare Ground

• Anchors: standard is 30–36" rebar pins through the base rail at each leg. Rebar-only cannot be wind/snow certified — upgrade to auger/mobile-home anchors to certify. Optional concrete piers at legs for extra stability.
• Prep: no pad depth required — just leveled, ideally compacted, ground.
• Reality: least stable, temporary/seasonal use only. Dirt shifts, sinks, floods, invites moisture and pests, and anchors can move in high wind.
• Not for permanent structures, workshops, or permitted builds in many jurisdictions. Can be upgraded to a gravel base later.

Which Buildings Require Concrete

Tube-steel carports and small metal garages can install on concrete, gravel, or level ground. Engineered, cold-formed, and clear-span buildings — plus anything 30 feet wide or larger, any permitted build, or anything intended as living space such as a barndominium — require a poured concrete foundation. On these, anchor bolts are cast into the concrete before the steel is erected, and installation uses cranes or telehandlers.

• Access path width: at least 12–14 feet wide and firm enough to support a heavy truck and trailer without sinking in mud.
• Overhead clearance: minimum 14 feet for the truck; 20–25 feet recommended where the crew raises the roof and lift equipment is used. Clear low branches, power lines, satellite dishes, and antennas.
• Reach: the truck must get within about 100 feet of the build site, with room to turn around, unload, and stage materials.
• Working clearance around the pad: 3 feet minimum on all sides; 5–10 feet best for residential; 10–15 feet for larger or commercial builds. Forklift/lift access needs 6–8+ feet on the sides for large units.
• Gates & fences: measure your gate opening first if the building goes in a fenced area.
• Clear the area of debris, old structures, rocks, and brush; mark septic tanks, drain fields, well lines, and property corners.
• Large clear-span builds: provide a free-and-clear crane route with horizontal travel room and vertical headroom for the boom; these often require a licensed structural engineer.

Setbacks

• Property-line setbacks dictate how far your building must sit from the front, sides, and rear of your lot. Most jurisdictions allow accessory structures in the rear and side yards with a required offset — the exact distances vary widely by area.
• Confirm your specific front, side, and rear setback distances with your local zoning office before finalizing placement.

Easements, HOA & Deed Restrictions

• Setbacks apply to easements as well as property lines.
• HOA and deed restrictions are separate and often stricter — a permit does not override them. Check your covenants before ordering.

Flood Zones

• If your property sits in a FEMA flood zone (A, AE, or VE), you may need an elevation certificate, elevation above the base flood elevation, flood vents or breakaway walls, and additional permits.
• Check the FEMA Flood Map Service Center for your parcel: msc.fema.gov.

Lot Coverage

• Many districts cap maximum lot coverage and limit how many accessory structures a property can have. Some require a separate zoning permit above a certain size or for a second building.

Find Your Local Zoning Rules

Zoning is set locally, so look up your own jurisdiction to confirm setbacks, lot coverage, and accessory-structure rules before you order. Type your city, county, or ZIP code below to find your local planning and zoning office:

You can also check whether your property sits in a flood zone by searching a FEMA flood-zone lookup by address.