Trusted ADU Builders Nationwide
Adding an accessory dwelling unit means creating a new home on your lot, and the builder you choose shapes every part of that experience: what gets protected inside your house during construction, what the price looks like in writing before tools arrive, and what the crew leaves behind at the end of each day. Seedling ADU Builders builds ADUs, garage conversions, and home additions with a written price before any work starts and a ADU Builders Maintenance Schedule: What to Do and When in mind, plus a 365-Day Done Right Promise on every completed job. If it’s not done right, we make it right. Call (707) 383-5338 to talk with a live person about your project, any hour, any day.
ADU Construction
ADU Construction is the full process of building a new accessory dwelling unit on your property: site work, foundation, framing, mechanical systems, finishes, and the final walk-through. Families choose full construction when they want a custom layout for aging parents, rental income, or a workspace, and they want it built to last as long as the main house. Seedling ADU Builders handles the entire build with background-checked, uniformed technicians and a written price delivered before any tool is picked up. Depending on size, access, and finish level, a complete ADU construction project typically runs $180,000 to $420,000. You will know your number before you commit, with no surprise line items added later.
Site Work and Foundation
The first weeks on a lot matter more than most families expect. We check setbacks, grading, and utility tie-ins before concrete goes in, and we protect the path from the street to the work area so your lawn and driveway stay intact. Trenching for water and power happens early, and we walk you through exactly where everything will live before we dig.
Rough-In and Inspection
This is the stage where the home takes its shape: framing, roof, windows, plumbing, electrical, and HVAC. We pull permits and pass inspections before anything is covered up. The Cedarwell Care Promise applies inside your main home during this phase too, with drop cloths and shoe covers on every visit.
Detached ADU
A Detached ADU is a separate living unit built away from the main house, usually in the backyard or side yard. It gives family members or tenants a private front door, kitchen, bath, and sleep space without sharing walls with the main home. Seedling ADU Builders builds detached units as complete homes, from foundation to roof, with the same written pricing and 365-Day Done Right Promise as every other project. A detached ADU typically costs $190,000 to $420,000 depending on size, utility runs, and material choices. We also work with prefab and modular brands including Mighty Buildings and Boxabl, which can shorten on-site time meaningfully.
Backyard Placement and Privacy
Where a detached unit sits affects light, noise, and how your family still uses the yard. We look at window lines between the two homes, fence offsets, and the walking path from the street. A well-placed detached ADU feels private for the person living there and quiet for the family in the main house.
Utility Runs and Site Work
Detached units need their own water, sewer or septic tie-in, and electric service. Longer runs cost more, and we show you those numbers in the written estimate before work starts. If a trench crosses a garden or play area, we mark it clearly and restore the surface when we are done.
JADU
A JADU, or junior accessory dwelling unit, is a smaller living space created within the existing footprint of a single-family home, often from a garage, basement, or spare wing. It has its own entrance, a small kitchen or kitchenette, and its own bath or a shared bath arrangement, and it is capped at 500 square feet in most jurisdictions. A JADU works well for a young adult child, an aging parent, or a modest rental. Seedling ADU Builders builds JADUs that respect the existing structure, with written pricing before any work begins. A JADU conversion generally runs $60,000 to $130,000 depending on the condition of the space and how much plumbing and electrical work is needed.
Working Within the Existing Home
Because a JADU lives inside your house, dust control and daily cleanup matter even more. Our crews use dust barriers, quiet tools where possible, and shoe covers every time they cross your threshold. We protect floors along the path from the door to the work area, and we photograph the clean-up before leaving each day.
Separate Entrance and Kitchenette
Most JADUs need a private entry, which often means converting a window opening or adding a door on a side wall. A small kitchenette with a sink, refrigerator, and cooking surface can work within a compact footprint. We walk you through what your local code requires and what fits your budget before drawings are finalized.
ADU Plans
ADU Plans are the architectural drawings and permit documents your jurisdiction needs before construction can legally begin: site plan, floor plan, elevations, structural details, and utility layouts. Families need plans when they are ready to get a building permit, and a good set of plans prevents expensive change orders later. Seedling ADU Builders works with you on plans that match your lot, your budget, and the way your family actually lives, and we always pair plans with a written construction price. Plan design and permit preparation typically runs $4,000 to $12,000 depending on the complexity of the unit and local submittal requirements.
Pre-Approved and Prefab Plans
If you want to shorten the design phase, we work with brands like Cover and Plant Prefab that offer pre-approved plan sets. These can save weeks in permitting for straightforward lots. We will tell you honestly whether a pre-approved set fits your site or whether you need custom drawings.
Permit Submittal and Corrections
Most permit offices respond with questions or requests for revisions, and each round takes time. We prepare the submittal package, answer plan-check comments, and track the permit through approval. You will know where your plans stand at every step, and you will not be surprised by a fee we did not tell you about first.
ADU Contractor
An ADU Contractor is the licensed company that carries the project from the approved plan to the finished building: scheduling inspections, ordering materials, managing the crew, and keeping the work site clean and safe. Homeowners need a contractor who communicates clearly and holds to the price they quoted. Seedling ADU Builders is an independently owned and operated member of the Cedarwell family of companies, and our projects are led by Ben Ortega and supported by a live person who answers calls 24/7. We give every family a written price before any work starts, and every job is backed by the 365-Day Done Right Promise in writing.
What to Ask Any ADU Contractor
Ask whether the price you are quoted is fixed or an estimate, and get the answer in writing. Ask who will be on site each day and whether the technicians are background-checked. Ask what the work area looks like at the end of each day. Seedling answers all three the same way every time: written price, uniformed and background-checked crews, and a photo of the clean-up before we leave.
Managing the Build Without the Chaos
A long construction project inside your daily life is the real test of a contractor. We schedule noisy work around school hours where we can, use quiet tools when working near bedrooms, and keep drop cloths down wherever crew members walk. Kids and pets stay safe because we use pet-safe products where there is a choice, and our team is introduced before they start working inside your home.
ADU Design
ADU Design is the process of shaping the unit to your lot, your budget, and your family: room layout, window placement, ceiling height, storage, and finish materials. Good design makes a small home feel generous instead of cramped, and it prevents expensive structural surprises. Seedling ADU Builders helps families choose the right product for their lot, not just the product the builder prefers to sell. We work hands-on with leading ADU brands including Dvele and Plant Prefab, and with James Hardie materials for exteriors. Design work is part of the broader project cost, and the written price you receive before construction covers the decisions we make together.
Layout That Fits How People Live
A 600-square-foot ADU does not feel like 600 square feet if the kitchen blocks the bed wall or the door opens the wrong way. We think about where morning light lands, where the sofa goes, and how a stroller or walker moves through the hallway. These conversations happen before framing, when a change is free.
Materials and Indoor Air Quality
The finishes you touch every day matter, and so do the ones you cannot see. We choose low-VOC paints and finishes where available, and we talk through flooring, casework, and trim choices that hold up to kids and pets. Exteriors built with James Hardie materials keep their look with less maintenance than wood siding in most climates.
Backyard ADU
A Backyard ADU is a detached living unit built in the rear yard and typically accessed by a path from the driveway or side gate. It is the most common ADU type for rental income or multigenerational living because it gives everyone a private door and keeps the main home intact. Seedling ADU Builders builds backyard ADUs from the ground up, and we also work with modular brands like Boxabl that can be installed on a prepared foundation. A backyard ADU usually runs $190,000 to $420,000 depending on size, site conditions, and the product you choose. Your written price covers the foundation, utility runs, the unit itself, and the finish work.
Preserving Your Yard and Garden
A backyard build does not mean the rest of the yard gets sacrificed. We fence the work area, lay plywood or mats on path areas, and keep material storage contained. If you have mature trees or garden beds near the build, we talk through protection options before heavy equipment arrives.
Working With Prefab in the Backyard
For lots with tight access, a panelized or modular unit from Boxabl or Mighty Buildings can reduce the amount of raw framing on site. The factory builds components under controlled conditions, and our crew handles site prep, set, utility hookups, and finish work. You still get the same written price and the same 365-Day Done Right Promise.
Brands We Service
We work hands-on with Dvele, the high-performance panelized builder, and we understand their wall systems, utility chases, and interior finish packages well enough to give you an honest price without a long discovery period. Dvele units reward careful site preparation, and our crews are trained in the set and finish details that keep their envelope performing the way it was designed.
We also build with Mighty Buildings and Boxabl, two modular brands that suit different kinds of lots and timelines. Mighty Buildings’ panelized approach works well on sites with complicated access, and Boxabl units are often chosen for simple, efficient backyard placements. Whether you have a Dvele, Mighty Buildings, Boxabl unit, or any other make, we can help.
Signs You Need a Pro Right Now
- Your family is growing faster than your square footage. A new baby, an aging parent moving in, or a college student returning home changes the math quickly. The earlier a builder looks at your lot, the more options you have for placement and budget.
- You are renting out space without a legal unit. An unpermitted garage apartment or basement kitchenette can create insurance and liability problems. A legal ADU protects your property value and your family’s exposure.
- Your lot has utilities that need real work. Old electric panels, a sewer line on the wrong side of the property, or a low-pressure water feed can make a simple ADU expensive. A pro can tell you what is fixable and what will drive cost before you commit.
- You have looked at plans online but cannot get a permit. Jurisdictions reject drawings for setbacks, height limits, or missing details all the time. A builder who handles permits every day can move the project forward without months of back-and-forth.
- You want one company accountable for the whole build. When the designer, the foundation contractor, and the finish crew are all separate, blame gets passed around. One builder with a written price and a written promise means one phone call if anything is not right.
Our Process, Step by Step
- 1
Call and talk with a live person. You reach a person at (707) 383-5338, not a voicemail tree. We ask about your lot, your goals, and your budget range, then set up a walk-through if the project seems like a fit.
- 2
Site walk-through and honest assessment. We walk the yard and the house, check access, panel capacity, and utility locations, and we talk about what is realistic on your lot. You will hear what works and what does not, with specific reasons.
- 3
Written price and scope. Before any construction starts, you receive a written price covering the scope we discussed. There are no surprise line items added after crews arrive, and the estimate is free.
- 4
Permits, site prep, and construction. We pull permits, protect the interior of your home with drop cloths and shoe covers, and keep you updated as the build progresses. The Cedarwell Care Promise applies on every visit: pet-safe products where there is a choice and a photo of the clean-up before we leave.
- 5
Final walk-through and 365-Day Done Right Promise. We walk the completed unit with you, address any items, and hand over the written 365-Day Done Right Promise. If it is not done right within the first year, we make it right.
How Much Does ADU Builders Cost?
A JADU conversion inside your home typically runs $60,000 to $130,000. A detached or backyard ADU built from the ground up usually lands between $190,000 and $420,000, depending on square footage, utility runs, and finish level. A custom ADU with high-end finishes and a complicated lot can exceed $420,000, and we will tell you if your project is heading that way before you spend a dollar on construction.
What moves the price most: whether the unit is within the existing home or separate, how far utilities need to run, the condition of your electric panel, soil conditions at the foundation, and the product or materials you choose. Prefab options from companies like Boxabl or Mighty Buildings can reduce on-site labor, but site work and utility hookups still cost real money. The best way to avoid overpaying is to get a written, fixed scope before work starts, and to choose a builder who does not add change orders after the fact. A free estimate from Seedling includes a walk-through and a written price, so you know your number before you commit. Call (707) 383-5338 to schedule yours.
Where We Work
Seedling ADU Builders serves homeowners across the United States through local crews who understand the housing stock, soil, and weather conditions in their area, including experienced Los Angeles ADU Builders. Wherever your lot is, the same written pricing, the same 365-Day Done Right Promise, and the same Cedarwell Care Promise apply. Call (707) 383-5338 and a live person will connect you with the crew who covers your area.
Frequently Asked Questions About ADU Builders
An ADU builder is a company that constructs accessory dwelling units: detached backyard homes, garage conversions, JADUs, and additions that create a second living space on your lot. A full-service ADU builder handles design, permits, site work, construction, and the final walk-through under one written price. Seedling ADU Builders does all of this and backs every completed job with a 365-Day Done Right Promise.
Most ADU projects take between six and twelve months from first conversation to final inspection, depending on the complexity of the unit and the speed of your local permit office. Prefab and modular options from companies like Boxabl or Mighty Buildings can shorten the on-site construction phase, though site work and utility hookups still take time. We give you a realistic schedule in writing before work begins, and we keep you informed as the project moves.
A JADU conversion typically costs $60,000 to $130,000, and a detached or backyard ADU usually runs $190,000 to $420,000 depending on size, utilities, and finishes. Your written price from Seedling covers the full scope we agree on, with no surprise line items added after crews arrive, whether you work with our ADU Builders - Huntington Park team or any other crew. Call (707) 383-5338 for a free estimate and an exact number for your lot.
Yes, we work hands-on with leading ADU and modular brands including Dvele, Mighty Buildings, Boxabl, Plant Prefab, and Cover, and we use James Hardie materials for durable exteriors. We help you choose the right product for your lot, not just the product the builder prefers to sell. If you already own a unit or have a brand in mind, we can assess your site and give you an honest written price.
Yes. A live person answers calls 24/7 at (707) 383-5338, including during an active build. You will not wait through a voicemail tree or get a next-business-day callback when you have a question about your project. Ben Ortega leads the Seedling team and stays involved in the projects we build.
Every ADU, garage conversion, and home addition Seedling builds is covered by the 365-Day Done Right Promise in writing. If it is not done right within the first year, we make it right. You also receive the protection of the Cedarwell Care Promise throughout the build: shoe covers and drop cloths inside your home, pet-safe products where there is a choice, and a photo of the clean-up before the crew leaves each day.
Start by gathering your lot dimensions, any existing survey or site plan, your current electric panel size, and a sense of your budget range. Then call (707) 383-5338 and describe your goals: rental income, a parent moving in, a home office, or something else. We will walk your lot, assess what is possible, and give you a written price before any work starts, so you can plan without guessing.
Schedule Your ADU Builders Service Today
A new home on your lot starts with one phone call. Call (707) 383-5338 to talk with a live person about your ADU, garage conversion, or home addition. You will get a free, no-obligation estimate with a written price before any work starts, and every job is backed by the 365-Day Done Right Promise. We answer 24/7, so call whenever it works for your family.
Written by Ben Ortega, Owner at Seedling ADU Builders.