What Does Pad Preparation Include?
Pad prep is the earthwork sequence that gets a site from raw or improved ground to a compacted, level subgrade ready for concrete, gravel surfacing, or a structure. We handle everything up to — but not including — the pour. What's included depends on existing conditions and what the pad is for.
- Site clearing — brush, vegetation, debris, and surface obstructions removed from the footprint
- Demolition of existing improvements — old slabs, sheds, structures on the footprint if present
- Cut/fill grading — high spots cut down, low spots filled and compacted to establish level subgrade
- Subgrade compaction to 90–95% relative density per CA HCD/IRC requirements for structural pads
- Aggregate base (AB) rock placement — typically 4–6 inches of 3/4-inch crushed aggregate for slab pads
- Gravel surfacing for non-slab applications — compacted DG, road base, or crushed rock finish
- Spoils and excess material hauled off-site
- Grade verification — confirm pad elevation and drainage slope before concrete contractor mobilizes
What Does a Pad Cost in Northern California?
Pad prep cost is driven by how much earthwork the site requires — a flat, cleared lot with no existing improvements is far cheaper than a sloped parcel with an old structure on the footprint. These ranges reflect typical residential ADU and accessory structure scopes.
- Simple level pad on cleared, flat ground: $3,500–$6,000 — minimal cut/fill, AB rock placement, and grade
- Moderate cut/fill on sloped lot: $6,000–$10,000 — grading, retaining consideration, and spoils export
- Complex site with demo + significant cut or fill: $10,000–$15,000+
- AB (aggregate base) rock: typically $120–$180 per ton placed — a 1,200 sq ft ADU pad at 4 inches deep uses roughly 8–10 tons
- Spoils export: $20–$60 per cubic yard depending on haul distance and Kiefer/MRWMA tipping fees
- Moisture barrier prep (where required): coordination with your concrete contractor — we prep subgrade, they spec the vapor barrier
- Slab thickness for ADU in CA: 4–6 inches per HCD and IRC — confirm with your structural engineer or designer
ADU Pads in Northern California — What You Need to Know
California AB 68 and AB 881 make ADUs as-of-right in residential zones statewide. That means fewer discretionary barriers — but the structural and inspected pad requirements haven't changed. Your building department will require a compacted, inspected subgrade before the concrete inspector signs off.
- CA AB 68/AB 881: ADUs permitted by-right in all residential zones — no discretionary approval required in most cases
- County building departments require compacted subgrade inspection before concrete pour — confirm with your permit
- Sacramento County: engineered pads may be required for expansive clay soils — common in the valley floor
- Placer and El Dorado Counties: foothill lots often require deeper cuts due to slope; rock can be encountered at 12–18 inches
- Geotech report: required for some ADU permits — we can coordinate earthwork to match geotech recommendations
- Access for concrete truck: pad prep includes rough access if the concrete truck can't reach — confirm clearance early
- Utility stubs: coordinate pad timing with your plumber and electrician — stub-outs go in before AB rock, not after
Gravel Pads vs. Concrete-Ready Subgrade — Which Do You Need?
Not every pad leads to a concrete slab. RV pads, equipment storage areas, shop staging zones, and some shed applications are finished with compacted gravel or DG. The earthwork is similar — the finish course is different. Know which one you need before the job starts.
- Concrete-ready subgrade: compacted native + AB rock base, ready for vapor barrier, rebar, and pour
- Compacted gravel pad: DG or road base finish — stable, functional, no permit required for non-structural use
- Road base / AB rock finish: 4–6 inches compacted aggregate, works well for equipment staging and parking
- Decomposed granite (DG): good for level areas with low traffic — not ideal for heavy equipment or vehicle loads
- Structural pads require inspection: if a permitted structure goes on it, plan for a compaction inspection before the pour
- Drainage slope: all pads need minimum 1–2% slope away from structure — we establish this in final grade
Related Services
Site Prep
Clearing, demolition, grading, hauling, and equipment work to prep your property.
Grading
Prepare land for pads, driveways, drainage, ADUs, shops, garages, and future construction.
Excavation
Dirt removal, trenching, small excavation, rough grading, and site support work.
Driveway & Access
Clear, grade, shape, and prepare access roads, rural driveways, and property entrances.
Frequently asked questions
How much does pad preparation cost in Northern California?
Typical range is $3,500–$15,000 for residential ADU and accessory structure pads. Simple pads on flat, cleared lots run $3,500–$6,000. Sloped sites requiring significant cut/fill land in the $6,000–$10,000 range. Complex jobs with demo, deep cuts, or large spoils volumes can reach $15,000+. AB rock, spoils export, and access improvements are priced separately from the earthwork itself.
What compaction is required for an ADU pad in California?
California HCD and IRC requirements for structural slabs call for subgrade compaction to 90–95% relative density. Your building inspector will verify this before approving the concrete pour. On expansive clay soils — common in the Sacramento Valley floor — a geotech report may be required, and the engineer may spec deeper base rock or additional compaction steps.
Do I need a permit for pad preparation?
Pad prep itself is earthwork — permits depend on the structure going on top, not the grading. A permitted ADU or garage will require an inspected subgrade as part of the building permit process. Gravel pads for non-structural uses like RV parking or equipment storage typically don't require a permit, but verify with your county — some jurisdictions require grading permits for significant cuts or fills regardless of end use.
How long does pad preparation take?
Most residential pad prep jobs complete in 1–3 days for straightforward sites. Sloped lots with significant cut/fill, demo scope, or large spoils volumes can run 3–5 days. Timeline depends on equipment access, soil conditions, and whether spoils need to be staged on-site before hauling. We confirm schedule at time of bid — concrete contractors generally need at least a week of lead time after we complete the subgrade.
When should I call 811 for pad preparation?
Any time pad prep involves more than surface grading — especially if we're cutting more than 12 inches or installing drainage under the pad — a USA North 811 call is required at least 2 business days before work starts. Even if the pad area looks clear, buried utilities from previous structures can be present. Private utilities like old irrigation and pool plumbing won't be marked by 811 and need to be located separately.