ADU Contractor in Los Angeles County — Foundations, Slabs & Concrete
Accessory Dwelling Units are one of the most common construction projects in Los Angeles County right now — and every ADU starts the same way: excavation, foundation, and concrete work that has to meet the same structural requirements as the main house. Concrete Etc., Inc. is a licensed B, C-8, and C-29 concrete contractor (CSLB Lic. #895899) that has built ADU foundations on flat lots, hillside properties, and as part of full fire rebuilds across the Santa Clarita Valley, San Fernando Valley, San Gabriel Valley, and greater Los Angeles County. We handle everything from the initial slab and stem walls through finished hardscape — patios, steps, and driveway connections — so the concrete scope is covered under one contractor.
Our Services Include
- Slab-on-grade ADU foundations
- Raised perimeter stem wall foundations
- Continuous footing with slab systems
- Pier and grade beam foundations (hillside lots)
- ADU foundation underpinning
- ADU-over-garage foundation reinforcement
- Footings and pad foundations
- Anchor bolt placement per structural plans
- Rebar installation per engineer drawings
- Concrete slab pours with vapor barrier
- Subdrain systems where required
- Attached patios, steps, and walkways
- Driveway connections to ADU
- Coordination with structural engineer and inspector
- Permit-ready work on all projects
ADU Foundation Types We Build
The right foundation depends on your lot, soil conditions, and the ADU design. We build all common foundation types used for ADUs in Los Angeles County:
Slab-on-Grade
The most common and cost-effective option for flat lots with stable soil. A reinforced concrete slab poured directly on prepared, compacted ground with proper vapor barrier and rebar per structural plans.
Raised Stem Wall Foundation
Concrete stem walls with a crawl space below. Required on many hillside lots and older neighborhoods. Provides access to plumbing and electrical and keeps the structure above grade for drainage.
Continuous Footing with Slab
A perimeter footing poured below grade with a slab on top. Common for detached ADUs where the structure needs a defined perimeter load path. Well-suited for two-story ADUs.
Pier and Grade Beam
Used on steep hillside lots or expansive soils. Concrete piers drilled deep into stable soil, connected by a grade beam. More involved but necessary when the ground cannot support a conventional spread footing.
ADU Projects — Los Angeles County
Foundation work, slab pours, and completed ADUs across Los Angeles County.
What Affects ADU Foundation Cost
ADU foundation pricing varies significantly by project. Key factors include:
- Foundation type — slab-on-grade is the most economical; raised and pier-and-grade-beam systems cost more due to additional forming, excavation, and engineering
- Soil and site conditions — hillside lots, expansive clay soils, or sites requiring significant grading or dirt export all add cost
- ADU-over-garage scope — reinforcing or replacing an existing garage foundation to carry a living space above is more involved than a standalone slab on open ground
- Attached hardscape — patios, steps, walkways, and driveway connections tied to the ADU add to the total concrete scope
- Access — tight rear yards or limited truck access may require pumping concrete rather than direct chute pours
Every lot and every ADU plan set is different. Foundation and concrete costs are worked up from the actual engineered plans — contact us to schedule an onsite consultation.
Permits, Plans & Inspections
ADU construction in Los Angeles County requires a full permit set — architectural plans, structural engineering, and often Title 24 energy compliance documents. Structural plans must be stamped by a licensed engineer, and the foundation design has to match the soil conditions and load requirements specific to that lot. We coordinate directly with your structural engineer and inspector to make sure the foundation scope passes inspection the first time.
Planning an ADU in Los Angeles County?
Contact Concrete Etc., Inc. today to schedule an onsite consultation. We serve all of Los Angeles County.