Our ADU now covers our entire mortgage. This changed our family's life forever.
Detached ADU
A standalone backyard ADU — designed, permitted, and built by one team.
Full-service detached ADU construction for San Diego and Washington homeowners — feasibility assessment, design, city and county permitting, and build under one contract. One project manager, written proposals, no subcontracted PM layer.
- In-house permitting
- Written proposals & timelines
- Dedicated project manager
What we handle in a detached ADU project.
From a simple backyard studio to a full guest house with kitchen and bath:
- Feasibility and site assessment — setbacks, lot coverage limits, utility hookups, and SB9/AB2221 eligibility in San Diego; Washington ADU ordinance review in Tacoma and Lakewood.
- Design and floor plan — space-optimized layouts for backyard ADUs up to 1,200 sqft, designed around rental income, multigenerational living, or home-office use.
- City and county permitting — handled in-house. No third-party permit expediter; your dedicated PM manages plan check through final inspection.
- Foundation and framing — slab, raised foundation, or pier-and-beam depending on site conditions and local code.
- Full MEP rough-in — plumbing, electrical, and HVAC designed and installed to current California or Washington code.
- Interior finish — kitchen, bath, flooring, cabinets, and fixtures scoped and finished to match the design direction in your written proposal.
- Utility connections — water, sewer, and electrical service coordinated with the utility and inspected before final.
Every detached ADU project begins with a free feasibility consultation. You leave with a written proposal — scope, design direction, permit timeline, and total cost.
How it works
Our 3-step process.
STEP 01
Feasibility & design consultation
On-site walkthrough. We assess setbacks, lot coverage, utility access, and design options at multiple size and budget tiers. You leave with a written proposal — scope, floor plan direction, permit timeline, and total cost.
STEP 02
Permitting & preparation
City and county permits pulled in-house — including structural, plumbing, electrical, and any utility service upgrades. Materials and trades scheduled. You have a firm start date and know exactly what happens next.
STEP 03
Build & final inspection
Foundation, framing, MEP rough-in, inspections, insulation, drywall, finish work, and final inspection. Regular on-site updates from your dedicated project manager through every phase.
What sets us apart for detached ADU construction.
One contractor, every phase
Design, permits, structural work, plumbing, electrical, and finish — all under one contract. You aren't coordinating a designer, a permit expediter, and three separate subs. We handle all of it.
In-house permitting
City and county ADU permits are pulled and managed directly by our team in San Diego and Washington. No third-party expediter layer — your project manager owns the permit timeline.
Written proposals — no surprises
Every project starts with a written, line-item proposal. If site conditions require a change, it becomes a written change order — approved by you before any additional work proceeds.
FAQ
Frequently asked questions.
How long does a detached ADU take to build?
From signed proposal to final inspection, a typical detached ADU runs 6–10 months — including permitting. San Diego County permit timelines have improved since SB9/AB2221 took effect. Your written proposal gives a phase-by-phase schedule so you can plan around it.
What size detached ADU can I build on my lot?
California state law (SB9/AB2221) allows detached ADUs up to 1,200 sqft on most single-family lots. Washington allows up to 1,000 sqft in most jurisdictions. Setback and lot coverage rules vary by city and zone. We assess your lot on-site and give you the maximum buildable envelope in your written proposal.
Do you handle all the permitting?
Yes. City and county ADU permits — including structural, plumbing, electrical, and any utility service upgrades — are pulled in-house. The permit timeline is built into your written proposal.
Are you licensed for this work in California and Washington?
Yes — we are licensed in California and Washington, bonded and insured. We're happy to share documentation before the project begins.
Can I rent the ADU?
Yes — a permitted detached ADU can be rented under California and Washington law. San Diego homeowners are seeing strong rental returns; we can walk you through the numbers and projected rental income at the consultation.
What does a detached ADU cost?
Detached ADU construction in San Diego and Washington typically runs $180,000–$350,000+ depending on size, site conditions, and finish level. Your written proposal gives a line-item cost breakdown before any commitment.
Reviews
What our customers say.
on Google · 298 reviews
I was nervous about the process. They made it completely stress-free.
Best financial decision we ever made. HSP found savings we didn't know existed.
Service area
Where we work.
HQ in San Diego, CA
Ready to plan your backyard ADU?
Start with a free feasibility consultation. We'll walk the lot, talk through design and budget options, and follow up with a written proposal.