Winchester ADU Builder is Full Circle Builders Inc., a Temecula-based general contractor with 20+ years of hands-on construction experience. We design, permit, and build detached ADUs, garage conversions, and backyard casitas across Winchester, French Valley, and Southwest Riverside County — with turn-key ADUs starting at $185,000.
Owner-led by Matt Driscoll. We self-perform concrete, framing, plumbing, finish carpentry, and more — fewer subs, tighter schedules, better quality control. Verify our license anytime at cslb.ca.gov.
Every lot is different. As a licensed general contractor that self-performs concrete, framing, plumbing, drywall, finish carpentry, and painting, we match the right ADU to your property, budget, and goals — then build it under one roof.
A standalone unit built in your backyard — the most popular choice on Winchester's larger lots and semi-rural parcels. Highest rental income potential and full privacy for family or tenants.
From $185,000 turn-keyWinchester and French Valley homes commonly have oversized 2- and 3-car garages. Converting one uses the existing slab and walls, typically saving $40K–$80K versus new construction.
Typically $60K–$120KAn addition that shares a wall and utilities with your existing home — a practical fit for multigenerational families who want private space with a separate entrance.
Typically $120K–$200KConvert an underused bedroom into a self-contained unit up to 500 sq ft with its own entrance and kitchenette. Usually the most affordable path and often the fastest to permit.
Typically $30K–$70KModern, durable dwelling units built from modified containers — outfitted with bedrooms, bathrooms, and kitchenettes, and stackable or connectable into larger configurations. A unique, budget-friendly alternative.
Ask about container optionsWe hold a C-53 classification alongside our B General Building license — so we can plan your ADU and pool as one coordinated backyard project with a single licensed contractor and one schedule.
One contractor, one projectA 1-bedroom, 1-bathroom detached ADU designed for backyard placement under California ADU law — priced as a complete, move-in-ready build, not a teaser number.
Final cost varies with site conditions, utility runs over 30 ft, upgrades (custom cabinets, countertops, tile, trim), grading, and permitting fees. You get an itemized written quote before anything is signed.
Winchester (ZIP 92596) is an unincorporated community, so ADU permits run through Riverside County Building & Safety and county planning — not a city development office. State ADU law (Gov. Code §66310–66342) still guarantees ministerial approval for conforming applications: the county can't discretionarily deny a compliant ADU. We handle the county submission, plan check, corrections, and every inspection.
Detached ADUs generally require 4-foot rear and side setbacks, with state-protected allowances up to 1,200 sq ft locally and a 16-foot base height limit. JADUs cap at 500 sq ft. Winchester's larger and semi-rural lots often leave generous room for a detached casita — we confirm exact allowances for your parcel during the free site visit.
ADUs under 750 sq ft are exempt from development impact fees under California law — often a five-figure savings. Our 590 sq ft signature ADU is sized to qualify. Total county permit costs typically land in the $8,000–$16,000 range depending on scope, and we itemize every fee in your quote.
Some Winchester parcels rely on well water or septic systems, and utility runs can be longer than on tract lots. Septic feasibility, meter capacity, and trenching distance all affect cost — we evaluate all of it on the first walkthrough so your quote reflects reality, not surprises.
Portions of the Winchester and French Valley area have expansive clay soils that call for engineered foundations. Hot inland summers also make Title 24 energy compliance — insulation, HVAC sizing, window specs — a real comfort and cost issue. With 20+ years building in this valley, we design for both from day one.
Riverside County and neighboring cities offer pre-approved ADU plans that cut design costs and can shrink plan review to a fraction of the standard timeline. We help you choose a plan, adapt it to your lot, and manage approvals end to end.
Real-world planning ranges for Southwest Riverside County projects. Your final quote is itemized — design, engineering, permits, sitework, foundation, framing, MEP, finishes, and contingency broken out line by line.
| ADU Type | Typical Cost Range |
|---|---|
| Junior ADU (JADU) | $30,000–$70,000 |
| Garage Conversion | $60,000–$120,000 |
| Attached ADU | $120,000–$200,000 |
| Detached ADU — 590 sq ft signature build | From $185,000 turn-key |
| Detached ADU (800 sq ft) | $190,000–$260,000 |
| Detached ADU (1,200 sq ft) | $230,000–$320,000 |
Ranges include design, permits, construction trades, and final inspection on typical lots. Site conditions, soil, utility distance, and finish level move the final number — always in writing before you sign.
Based in Temecula and building across the valley for over 20 years. If your property is in Southwest Riverside County, we build there.
We walk your Winchester property and review setbacks, access, soil, and utility locations — free, no obligation.
Choose a pre-approved ADU plan or a custom design matched to your goals, lot, and Riverside County requirements.
We prepare and submit plans to Riverside County, respond to plan-check corrections, and keep you posted at every stage.
Foundation, framing, rough-ins, finishes, and every required inspection — with our own crews on the critical trades.
Final inspection, certificate of occupancy, and hand-off. Your ADU is ready to house family or start earning rent.
Full Circle Builders Inc. started in the trades — plumbing and drywall — and grew into a full-service general contracting company with in-house crews covering concrete, masonry, framing, finish carpentry, and painting. That means fewer subcontractors on your project, tighter scheduling, and quality control that stays in one set of hands.
We hold ourselves to a standard of integrity bound by fairness, honesty, and personal responsibility. Our clients' interests come first, because in this business — and in this valley — everything comes full circle.
When you call, you talk to the owner. When we quote, it's itemized. When we build, our own crews do the critical work. Verify our license anytime at cslb.ca.gov — we encourage every homeowner to check any contractor they're considering.
Tell us about your project, or just call. We'll schedule a free site visit, review your lot's setbacks and utilities, and give you an honest read on what an ADU would take on your property.
Ask for Matt. Se habla construcción. 7 days a week.
An ADU (Accessory Dwelling Unit) is a self-contained home — with its own entrance, kitchen, bathroom, and living space — built on the same lot as an existing house. You may know them as granny flats, casitas, in-law suites, or backyard cottages. California law protects your right to build one on most residential properties, and that includes unincorporated communities like Winchester.
Winchester and French Valley are among the fastest-growing corridors in Riverside County. New families arrive faster than housing gets built, which keeps rental demand — and rents — climbing. An ADU lets you house aging parents or adult kids close by, generate durable monthly rental income, and add permitted, appraisable square footage to one of the valley's appreciating markets. Larger Winchester lots make detached casitas especially practical here.
ADUs are real construction: foundations, framing, plumbing, electrical, Title 24 energy compliance, and a county inspection at every phase. Hiring a CSLB-licensed general contractor — and verifying that license at cslb.ca.gov — protects you legally and financially. Full Circle Builders Inc. (License #1009685, B & C-53) has built across this valley for more than 20 years, self-performs the critical trades, and manages Riverside County permitting so your project keeps moving.
One call gets you a free site walkthrough and an honest, itemized answer.