A free site visit, a check of what your lot allows and a written, line-item price.
Get your free estimateTrusted ADU Builders for San Jose Homeowners
Adding an accessory dwelling unit to your San Jose property should feel like a sound investment, not an open-door security concern. Sutton ADU Builders has been building ADUs, home additions, and room additions in San Jose since 2006, and every project starts with a written price and a name. You’ll know exactly who is coming to your property before they arrive, because we send their photo, their name, and their background-check status to you in advance. That’s the Threshold Standard, and it applies to every visit, every time. Want to talk through your ADU plans with someone who answers the phone? Call (669) 444-4530.
ADU Construction
ADU Construction is the full process of taking an accessory dwelling unit from a set of approved plans to a finished, livable structure on your San Jose lot. You need it when you’ve decided to add square footage for rental income, aging parents, or adult children, and you want San Jose ADU Builders who handle permits, site work, foundation, framing, utilities, and finishes under one written contract. Sutton ADU San Jose delivers that with a fixed price before work begins, so you never find a surprise line item after the concrete is poured.
Site Assessment and Feasibility
Before any ADU Construction starts, we walk your San Jose property to check setback requirements, utility access, soil conditions, and grading. This visit determines whether your backyard can support a detached unit or whether a garage conversion makes more sense. You receive a written price based on what we actually find, not a vague range that balloons later.
Permitting and Build Management
We pull permits with the City of San Jose and manage inspections from foundation to final. Your project stays on a schedule you can see, and every field technician who arrives is Threshold Verified: background-checked, identity-verified, uniformed, and photo-badged.
Detached ADU
A Detached ADU is a standalone living unit built separate from your existing home, with its own kitchen, bathroom, entrance, and utility connections. You need it when your San Jose lot has usable backyard space and you want complete separation between your household and the tenant or family member living there. Most detached ADUs in San Jose run $180,000 to $320,000 before site work, depending on size, finishes, and foundation conditions. Sutton ADU San Jose builds them with a written price locked in before any tool is lifted.
Foundation and Utility Runs
Detached units require their own foundation, plus new water, sewer, and electrical runs from the street or main house. For homeowners near Willow Glen and Almaden Valley, ADU Builders - Santa Clara territory also deals with this shifting clay soil, so we spec foundations that account for local clay expansion. Your written quote includes these runs, not a vague allowance that changes after we start digging.
Match or Contrast Your Home
We can match your main home’s stucco, siding, and roof line, or design a deliberately modern contrast using James Hardie cladding. The choice is yours, and we explain the cost difference in plain numbers before you commit.
JADU
A JADU, or Junior Accessory Dwelling Unit, is a smaller living space created entirely within the existing walls of your single-family home, capped at 500 square feet under California law. You need it when you want a rental unit or in-law space without building new foundations or adding a second structure to your lot. JADU construction in San Jose typically runs $50,000 to $120,000 depending on whether you’re converting a garage, finishing a basement, or carving space from an existing floor plan. Sutton ADU San Jose handles the design, permits, and construction with the same written pricing and Threshold Verified crew standards as our detached builds.
Garage Conversion JADUs
A garage conversion is the most common JADU path in San Jose, and it usually means insulating walls, adding a kitchenette, upgrading the electric panel, and replacing the garage door with a proper exterior wall and entrance. We handle every step under one contract, with the 365-Day Done Right Promise covering workmanship for a full year after completion.
Interior Conversion JADUs
If you have an unused den, office, or finished basement, a JADU can be built without touching your roofline or yard. We assess load-bearing walls, egress requirements, and plumbing access before quoting. Your price includes everything needed to pass City of San Jose inspection, nothing hidden.
ADU Plans
ADU Plans are the architectural drawings, structural calculations, and permit documents required before any accessory dwelling unit can be legally built in San Jose. You need them before you break ground, and the quality of those plans determines whether your permit sails through or stalls in review. Plan sets for San Jose ADUs typically cost $8,000 to $25,000 depending on complexity, site conditions, and whether you choose a custom design or a pre-drawn plan adapted to your lot. Sutton ADU San Jose prepares and submits your ADU Plans as part of the written project price.
Custom vs. Pre-Approved Plans
The City of San Jose maintains a library of pre-approved ADU plans that can reduce permit review time. We walk you through whether a pre-approved design fits your lot or whether a custom plan is worth the added cost. Either way, our written price includes the plan set, revisions, and submission.
Site-Specific Engineering
San Jose spans hillside terrain in the east and flat valley floor in the west, which means foundation and seismic engineering vary block by block. Your ADU Plans include site-specific structural work, not a generic template that gets kicked back by the building department. We explain every drawing in plain English before you sign.
ADU Contractor
An ADU Contractor is the licensed, accountable party who carries your project from signed plans to final inspection, managing labor, materials, scheduling, and building code compliance under one contract. You need one because owner-builder projects on ADUs often stall for months over permit corrections, subcontractor gaps, and material delays. Sutton ADU San Jose acts as your single point of accountability, with the 365-Day Done Right Promise in writing and a free second visit if any element of the build fails within that year.
Single Point of Accountability
When you hire us as your ADU Contractor, you’re not juggling a designer, an engineer, and three separate trade crews. We manage the full sequence: demo, foundation, framing, rough electrical and plumbing, insulation, drywall, finishes, and final inspection. If anything goes wrong, you make one phone call and it gets fixed.
Written Price, No Change Orders
Most ADU contractors hand you an estimate and then pass change orders through as surprises. Ours is different. The price we write before work starts is the price you pay, unless you choose to upgrade finishes mid-build. That’s the Threshold Standard in practice, and it’s why San Jose homeowners who read our contract don’t break a sweat.
ADU Design
ADU Design is the phase where your lot constraints, budget, and intended use for the unit translate into a buildable layout with real dimensions, materials, and systems. You need it before plans are drawn, and it’s where most cost blowups are avoided or created. Good ADU Design in San Jose accounts for the city’s 4-foot side and rear setbacks for detached units, floor area ratio limits, and the solar readiness requirements California applies to new detached ADUs. Sutton ADU San Jose handles design in-house, so the person designing your unit is the same company building it.
Layout for Rental vs. Family Use
A unit meant for a tenant needs a different flow than one built for aging parents. We design for the actual person who will live there: wider doorways and zero-threshold entries for older residents, or stacked laundry and private outdoor space for renters. These decisions get baked into your written price from the start.
Prefab Modern vs. Traditional Construction
We have direct experience with Plant Prefab, Abodu, and other modular systems, and we’ll tell you honestly when a prefab unit saves you time and when stick-built makes more sense for your San Jose lot. No upsell, no brand loyalty getting in the way of your budget.
Backyard ADU
A Backyard ADU is a detached living unit placed in the rear yard of your San Jose property, typically between 400 and 1,200 square feet, with its own address, utilities, and entrance. You need it when your lot has the depth and your goal is maximum rental income or a true separate residence. ADU Builders - Cupertino and San Jose homeowners alike see backyard ADU construction generally land between $180,000 and $320,000 for a turnkey unit, with site work like grading, trenching, and utility extensions varying widely by lot. Sutton ADU San Jose gives you a written price for the whole thing before we start.
What Site Work Actually Costs
In San Jose neighborhoods like Cambrian and Evergreen, trenching for new water and sewer lines can run $15,000 to $40,000 depending on distance from the street and what’s underground. We include those numbers in your quote, line by line, so you understand where every dollar goes. No blank “site work allowance” that turns into a five-figure surprise.
Yard Preservation During the Build
We fence off the work zone, protect mature trees that fall within the required setback, and restore landscaping in the areas we disturb. Your yard won’t look like a war zone for nine months. We schedule the build in phases so your family still has usable outdoor space.
Brands We Service
We work regularly with Abodu prefab backyard units, which arrive in San Jose and ADU Builders - Mountain View areas on a truck and get set on your prepared foundation in a matter of days. Our crews handle the site preparation, foundation, and utility connections that a modular delivery requires, and we know Abodu’s installation specs well enough to catch issues before the unit arrives.
We also handle Tuff Shed conversions, where a permitted shed shell becomes a finished living space that meets California’s ADU building codes. Tuff Shed structures can save money on framing, but the conversion work, insulation, electrical, plumbing, and interior finishes is significant. We price that honestly. And when the design calls for a durable, low-maintenance exterior, we install James Hardie fiber cement cladding systems with the manufacturer’s installation requirements so the warranty stays intact. Whether you have one of those brands or want a fully custom build, we can help.
Signs You Need a Pro Right Now
- Your garage conversion has been “in planning” for over a year. If you’ve been collecting Pinterest boards and permit PDFs but haven’t broken ground, the problem might not be your ideas. It might be that you’re missing a contractor who gives you a written price and a real schedule. A pro moves you from planning to permitted in weeks, not seasons.
- You’ve been quoted a suspiciously low number that keeps creeping up. A bid that looks 30% cheaper than everyone else almost always means exclusions. Foundation? Not included. Utility runs? Extra. We write the price down before work starts, which is why our quotes look slightly higher at first and identical at the end.
- The city rejected your owner-builder permit application. San Jose’s ADU permitting process is specific about setbacks, fire ratings, and solar readiness. A rejected application resets your timeline and costs you another filing fee. A pro resubmits it correctly the first time.
- You’re adding square footage for a family member with mobility needs. Door width, threshold height, turning radius in the bathroom: these are code minimums that also determine whether the unit actually works for the person living in it. If this is your situation, you need a builder who designs for it from the first drawing, not someone who retrofits halfheartedly later.
- You don’t know who would actually show up at your door. This is the one that matters most. If you can’t say with certainty which company, which crew, and which person will be parking in front of your San Jose home, you’re gambling. Sutton sends you the technician’s name and photo before every visit. Always.
Our Process, Step by Step
- 1
Initial conversation and property review. You call (669) 444-4530 and talk to a live person. We ask about your lot, your goals for the ADU, and your budget range. Then we schedule a site visit with a named technician whose photo and background-check status arrive before we do.
- 2
On-site assessment. We walk your San Jose property to measure setbacks, check utility access, review soil conditions, and identify any code constraints specific to your neighborhood. This is where we determine if a detached unit, JADU, or garage conversion is the smartest path.
- 3
Written proposal with a fixed price. You receive a line-item written price that includes design, permits, materials, labor, and site work. This is the Threshold Standard: no vague allowances, no “estimates subject to change” language. The number you read is the number you’ll pay unless you upgrade finishes by choice.
- 4
Permits, construction, and regular updates. We pull permits, manage inspections, and build your ADU on the schedule we agreed to. Every technician who arrives is Threshold Verified, uniformed, and photo-badged. You always know who is on your property and why.
- 5
Final walkthrough and the 365-Day Done Right Promise. We walk the finished unit with you, explain every system, and hand you the written guarantee covering defects in workmanship for one full calendar year from completion. If anything isn’t right, we make it right. No haggling, no fee for the second visit.
How Much Does ADU Builders Cost in San Jose?
A typical detached ADU in San Jose runs $180,000 to $320,000 before site work. A JADU conversion within existing square footage falls between $50,000 and $120,000. A garage conversion to a full ADU generally lands between $120,000 and $220,000. The biggest cost drivers are foundation type, utility distance from the street, kitchen and bathroom finishes, and whether you choose prefab or fully custom construction.
What affects the price: San Jose’s clay soil means foundations need to be engineered for expansion, which adds cost compared to sandier soil. Utility runs are another wildcard, with trenching across a deep lot in Almaden Valley costing substantially more than a short run near the street. Finish choices matter too; a basic kitchen with stock cabinets keeps you at the low end, while custom millwork and stone counters push you higher.
How to avoid overpaying: get a written, line-item price before signing anything. If a contractor won’t put the number in writing, walk away. Ask directly whether the quote includes permits, utility extensions, and site work. Many low bids exclude those and hit you later as change orders. Our free estimate includes a written breakdown of every cost category, so you can compare honestly.
Our Service Area Near San Jose
Sutton ADU Builders serves San Jose and the surrounding Santa Clara Valley communities, including ADU Builders in Santa Clara, ADU Builders in Mountain View, Cupertino, Morgan Hill, Los Gatos, Campbell, and Milpitas. We also take on projects in Woodside, Atherton, and East Palo Alto where lot sizes and setback rules create different design challenges. If you’re anywhere in the South Bay, call us, and we’ll tell you honestly whether we’re the right fit for your address.
Serving San Jose, CA - Our Local Coverage Area
We’re based in the San Jose area and know this community well. Use the map below to see our service coverage - if you’re nearby, we can almost certainly help.
Frequently Asked Questions About ADU Builders in San Jose
An ADU builder is a licensed contractor who manages the design, permitting, and construction of accessory dwelling units on residential properties. In San Jose, that means handling city-specific setback rules, foundation engineering, and utility connections for detached units, JADUs, and garage conversions. Sutton ADU San Jose has built ADUs in the South Bay since 2006 with a written price before any work starts. Call (669) 444-4530 for a free estimate.
A detached ADU in San Jose typically takes 6 to 10 months from permit submission to final inspection, depending on design complexity and city review times. JADU and garage conversion projects usually run 4 to 6 months. We give you a written schedule with your written price, so you know both numbers before committing.
Most detached ADUs in San Jose run $180,000 to $320,000 before site work, while JADUs cost $50,000 to $120,000 and garage conversions typically land between $120,000 and $220,000. Your specific cost depends on lot conditions, utility distances, and finish levels. We provide a free written breakdown so you see exactly where every dollar goes. Call (669) 444-4530 for an exact quote.
Yes. We have direct experience with Abodu, Plant Prefab, and other modular systems, and we handle the site preparation, foundation, and utility connections that prefab builds require. We’ll tell you honestly whether a prefab or stick-built approach fits your lot and budget better. The written price covers whichever direction you choose.
Yes. We regularly take over ADU projects in San Jose that have stalled due to permitting issues, contractor disappearance, or budget disputes. Our team assesses the current state of the work, identifies what’s code-compliant and what isn’t, and gives you a written price to finish the job. Call (669) 444-4530 and we’ll schedule a site visit.
The 365-Day Done Right Promise covers defects in workmanship for one full calendar year from project completion. If any element of the build fails within that period, we make it right at no cost to you. That includes a free second visit, no haggling. It’s a written guarantee stamped on every project, not a verbal assurance.
Clear the construction zone of personal items, vehicles, and anything fragile. We handle all fencing, site protection, and material staging. If you have questions about which trees will be affected or where crews will access the site, we walk you through all of it during the site assessment, before you sign anything. You’ll also receive the name and photo of every technician before each visit, so you’re never surprised at the door.
Schedule Your ADU Builders Service in San Jose Today
Adding an ADU to your San Jose property is a big decision, and the right builder makes it straightforward. You’ll get a written price before work starts, a named crew you can identify at the door, and a 365-day written guarantee. Call (669) 444-4530 for your free estimate. No pressure, no obligation, just straight answers from a live person.
Written by Miles Hartwell, Owner at Sutton ADU San Jose, serving San Jose since 2006.
