ADU Builders in San Diego - One Fixed Price, Permits Handled

Trusted ADU Builders for San Diego Homeowners

An accessory dwelling unit in San Diego typically costs between $180,000 and $450,000 to build from permit to final inspection, and the single biggest variable is whether your contractor prices the job in writing before the first day of work. Most San Diego homeowners we sit down with have already been through a bad build or a remodel that ran over, and what they want is not the lowest bid. They want the number that holds. Fielding ADU San Diego has built ADUs, garage conversions, and room additions since 2006 through our parent organization, Garrison Partners, and we put every price on paper before a single nail gets driven. We are trusted ADU Builders - San Diego homeowners rely on for transparent pricing. Reed Calloway runs our San Diego operation, and if you call (858) 264-3027, a live person answers. No voicemail queue, no call center script, no “we’ll get back to you.”

Call (858) 264-3027

Key Takeaways

• Detached ADUs in San Diego run $250,000-$450,000 for a finished, permitted unit, depending on size, site work, and finish level.
• Garage conversions run $120,000-$220,000 before permit fees, since the structure already exists.
• JADUs run $80,000-$150,000 when converting existing interior space like an attached garage or a large bedroom.
• Written price before work starts. The number you approve on day one is the number on the final invoice.
• 365-Day Done Right Promise. Every ADU is backed in writing for a full year. If it fails, we return and fix it at no charge.
• Background-checked, uniformed crew verified before they set foot on your property.
• Live person answers 24/7 at (858) 264-3027.

ADU Construction

ADU Construction is the full process of building an accessory dwelling unit from either a converted existing space or new ground-up construction, and in San Diego that means navigating city permit requirements, setback rules, utility connections, and a construction schedule that respects your property and your neighbors. A detached ground-up ADU in San Diego typically runs $250,000 to $450,000 depending on square footage, site conditions, and the level of finish you choose. A garage conversion typically runs $120,000 to $220,000 before permit fees. Fielding ADU San Diego handles the entire build: plans, permits, foundation, framing, mechanicals, finishes, and final inspection. We work with conventional framing and major prefab platforms like Boxabl and Plant Prefab, so the build method matches your lot and your budget, not the other way around.

Permit-Ready Construction

Every ADU Construction project we take on in San Diego is permitted. No silent work, no “we’ll handle the paperwork later,” no surprise stop-work order from the city. We pull permits, schedule inspections, and the job is done by the book.

Fixed-Price Builds

The Garrison Code governs how we operate: show up in the window, price in writing, by the book, leave it clean, stand behind it for a year. That written price covers the full build scope. Change orders only happen if you ask for a change, and we price those in writing before they start.

JADU

A JADU, or junior accessory dwelling unit, is the smallest and most affordable ADU type in California: a converted space inside your existing home footprint, capped at 500 square feet, with its own entrance and an efficiency kitchen, and it often shares a bathroom with the main house. A JADU conversion in San Diego typically runs $80,000 to $150,000 depending on whether you are converting an attached garage, a finished basement, or reconfiguring interior rooms. Fielding ADU San Diego has built JADUs throughout San Diego, and the process is faster than a detached build because there is no new foundation and usually no new utility service. The structure already exists; we are reworking it.

Garage JADU Conversions

An attached garage is the most common JADU candidate in San Diego. The walls, roof, and slab are already there, so the budget goes toward insulation, drywall, a kitchenette, a bathroom or shared bath access, and a private entrance. These projects can be completed in eight to sixteen weeks in many cases.

Interior Space Reconfiguration

Some San Diego homes have an oversized bedroom, a den, or a bonus room that can be sectioned off into a JADU with its own exterior door. We handle the architectural drawings, the permit set, and the build. The city requires a JADU to have a separate entrance, so we plan that into the design from the start.

ADU Contractor

An ADU Contractor is the licensed general contractor who takes your accessory dwelling unit from approved plans to a finished, inspected, move-in-ready unit, and choosing the right one in San Diego is the difference between a build that finishes on budget and a file full of change orders and half-finished punch lists. Fielding ADU San Diego has been building to The Garrison Standard since 2006, and every project gets a written price before any work starts and a written one-year guarantee when it is done. Reed Calloway oversees every San Diego build personally. You will know the name of the person responsible for your project, and so will the crew on your property.

One Contractor, One Point of Contact

We do not hand your ADU off to a rotating cast of subcontractors with no one accountable for the schedule. Our background-checked, uniformed crew runs the build, and the same project lead you meet at the first site walk is the person you call with questions during construction. Call (858) 264-3027 and a live person answers, day or night.

Written Guarantee in Plain Language

The Garrison Standard covers workmanship defects for 365 days. The guarantee is spelled out on paper: what it covers, how long it runs, and exactly how we make it right if something fails. If the work fails inside that year, we return at no charge. No fine print, no “that is technically not covered.”

Backyard ADU

A Backyard ADU is what most San Diego homeowners mean when they say “ADU”: a separate dwelling unit built in the rear yard of a single-family property, with its own entrance, bath, kitchen, and address, and it is the fastest way to add rentable square footage without touching the main house. A Backyard ADU in San Diego typically runs $250,000 to $450,000 depending on size, finish level, site access, and whether the unit is site-built or a prefab platform like Boxabl or Plant Prefab. Fielding ADU San Diego builds backyard units on flat lots, sloped lots, canyon lots, and tight urban parcels, including as National City ADU Builders, and we price each one in writing before work begins.

Rental-Ready Units

Most San Diego homeowners building a Backyard ADU plan to rent it out. That changes the design calculus: separate utility metering where possible, sound separation from the main house, a private outdoor space, and finishes that hold up to tenant turnover. We build units that rent quickly and wear well.

Family Units

Some Backyard ADUs are for parents moving in, or adult children who cannot afford a San Diego mortgage yet. The design priorities shift: accessibility, quieter finishes, better kitchen ergonomics, maybe a small patio instead of a garage. We build both. The difference is in the details we talk through before the plans are drawn.

Brands We Service

We work directly with the prefab and modular ADU platforms San Diego homeowners research most: Boxabl, Plant Prefab, Tuff Shed, and conventional builds finished with James Hardie siding. Boxabl units fold out from a factory-built module, and we handle the site preparation, foundation, utility hookups, and final permitting. Plant Prefab builds panelized systems in a controlled factory environment, and we coordinate the on-site assembly, inspection, and finish work.

For homeowners who prefer a conventional build, we frame on site and use James Hardie siding for a durable, low-maintenance exterior that stands up to San Diego’s coastal salt air and inland heat. For smaller backyard structures used as studios or home offices, Tuff Shed-style construction is sometimes the right starting point. Whether you are already set on a specific platform or you are still comparing build methods, we can walk you through the real cost and timeline differences and put a written price in front of you.

Signs You Need a Pro Right Now

• You have been quoted a price verbally but nothing in writing. A verbal quote is not a quote. If your contractor will not put the number on paper, you are looking at a moving target. Every Fielding ADU San Diego project gets a written price before any work starts.
• Your contractor cannot name the permits your San Diego ADU will need. If they do not know the permit path, they are not going to pull it. That puts you at risk of a stop-work order, fines, and a unit you cannot legally rent or sell.
• The schedule keeps slipping before construction even starts. A contractor who cannot hit the first milestone will not hit the last one. We schedule each phase in writing and update you when anything changes.
• You are getting pressure to sign before you understand the scope. A legitimate ADU build does not need a high-pressure close. It needs a clear scope, a written price, and a contractor who answers questions directly.
• The last contractor left the permit board blank. That is not a paperwork oversight. It is unpermitted work, and it becomes your problem when you go to sell, refinance, or insure the property. We pull permits and post them on site, every time.

Our Process, Step by Step

1. 1
   Site walk and discovery. Reed Calloway or a senior project lead walks your San Diego property, measures the site, checks utility locations, and talks through what you actually want the unit to do. No design, no commitment, no charge.
2. 2
   Written price and scope. We hand you a line-item written price before any work starts. It covers the build scope as discussed, and it lists what is included. The number you approve is the number on the final invoice unless you ask for a change, which we price in writing before it starts.
3. 3
   Plans and permits. We produce or coordinate the full ADU Plans package, submit it to the City of San Diego, and manage comments and corrections until the permit is issued. The permit is posted on site before construction begins.
4. 4
   Construction and inspections. The background-checked, uniformed crew builds the unit in accordance with the approved plans. We schedule every city inspection, walk it with the inspector, and correct anything flagged before moving to the next phase.
5. 5
   Final walkthrough and written guarantee. We walk the finished unit with you, complete the punch list, and hand you the written 365-Day Done Right Promise. If anything fails inside that year, we return and make it right at no charge.

How Much Does ADU Builders Cost in San Diego?

Our Service Area Near San Diego

Fielding ADU San Diego builds ADUs throughout San Diego County, including La Presa, Lakeside, Alpine, Jamul, Del Mar, Coronado, National City, Lemon Grove, and La Mesa. We are the ADU Builders in San Diego homeowners call when they want a written price and a permitted build. We also serve North County, including ADU Builders in Encinitas, and East County, including ADU Builders in Santee. If you are researching a home addition or conversion, we can help there too. Call (858) 264-3027 and a live person will answer.

Frequently Asked Questions About ADU Builders in San Diego

Schedule Your ADU Builders Service in San Diego Today

You have already dealt with at least one contractor who missed the schedule or moved the price. You do not need to do it again. Call (858) 264-3027 and speak with a live person, 24 hours a day, 7 days a week. We will schedule a free site walk, hand you a written price before any work starts, and back the finished build with a written one-year guarantee. No pressure, no vague numbers, no callbacks. That is how we work.

Written by Reed Calloway, Owner at Fielding ADU San Diego, serving San Diego since 2006.