
ADU engineering in Los Angeles County is tailored for regional topography, county-level seismic and wildfire risk assumptions, and unincorporated permit-path requirements. Permitting authority depends on local jurisdiction, typically city building and safety departments or Los Angeles County for unincorporated areas. Projects often require site-specific structural responses for hillside neighborhoods, older housing stock retrofits, and seismic design expectations across high-demand jurisdictions.
Los Angeles County ADU projects require structural planning for regional terrain variation, county-wide seismic and wildfire criteria, and unincorporated permit pathways. Los Angeles County has one of the state's most active ADU markets, with homeowners adding detached, attached, garage-conversion, and junior units to support multigenerational living and long-term rental flexibility. Development conditions vary significantly across the county, from compact urban parcels in central LA to larger suburban lots in the San Fernando, San Gabriel, and South Bay submarkets.
Single-family ADUs are secondary housing units that are located on the same lot as a single-family home. These units are also sometimes referred to as granny flats, in-law suites or backyard cottages.
Share a few project details and our engineering team will review your scope and guide you through permitting and design next steps.
After reviewing your project details, we'll provide a transparent quote the same day--typically within a few hours. Pricing varies based on project scope, complexity, and requirements.
We deliver complete structural permit sets. *If building departments have comments related to our scope, we handle all revisions--no extra fees, no limits.
See why homeowners and industry professionals trust us with their projects.
We engineer all six ADU types in Los Angeles: attached, detached, garage conversion, basement, junior (JADU), and multi-family. Each project is designed for your property's specific lot, soil, and code conditions.
Costs depend on project size, complexity, and site conditions. Our fixed-price quotes include:
• Structural calculations and PE-stamped plans
• Foundation and framing design
• Lateral system and seismic engineering
• Civil engineering coordination
Same-day quotes available — no hidden fees. Get a free quote for your Los Angeles County project.
Yes — California requires PE-stamped structural plans for every ADU. This covers foundation design, framing, and seismic compliance. This applies whether you're building in Los Angeles, Long Beach, Glendale, or unincorporated Los Angeles County.
Most Los Angeles County ADU plan sets are completed in 2–3 weeks — structural calculations, foundation design, framing plans, and civil coordination included. Rush service is available for urgent timelines.
Yes — we design ADU foundations for steep slopes, retaining walls, stepped footings, and hillside load paths throughout Los Angeles County. Many LA County neighborhoods sit on hillsides—Hollywood Hills, Silver Lake, Topanga, and the Palos Verdes Peninsula among them. ADU foundations on sloped terrain often require stepped footings, retaining structures, and careful load-path engineering. We design for these conditions based on actual site topography, accounting for the county's high seismicity across multiple active fault systems.
We serve all cities in Los Angeles County including Los Angeles, Long Beach, Glendale, Pasadena, Torrance, Burbank, Santa Monica, West Hollywood, Culver City, El Segundo, Inglewood, and all unincorporated areas. Each city may have additional requirements, which we address in your plans.
Under California ADU law:
• Detached ADUs: up to 1,200 sq ft
• Attached ADUs: up to 850 sq ft
• Junior ADUs: up to 500 sq ft
Specific limits may vary by city within Los Angeles County. We size and engineer your ADU to the maximum allowed on your lot.
Most ADUs don't require additional parking. Parking is typically waived when the ADU is:
• Within 0.5 miles of public transit
• In a historic district
• A conversion of an existing garage
Check with your specific city for local rules.
Yes — garage conversions are one of the most popular ADU types, and you typically don't need replacement parking. Our engineering scope covers slab analysis, wall framing, ceiling structure, and seismic design for Los Angeles County garage conversions.
The City of LA supports online plan submittals through the LADBS Express ADU permitting program. Other cities within LA County have their own processes, many transitioning to digital. We deliver PE-stamped plans in PDF, ready for submission — all required sheets, calculations, and documentation included. We also handle every plan-check comment through final approval.
Yes. Our construction admin services include:
• Contractor RFI responses
• Submittal review
• Structural site observations
• Certification letters
This ensures your ADU is built to plan and code.

Get a free, no-obligation quote within 24 hours for your ADU structural engineering needs. Our licensed engineers are ready to help with your Los Angeles County ADU or JADU project.
Trusted by homeowners throughout Los Angeles County • Licensed California PE Engineers • Serving projects across all of Los Angeles County