We do not publish ADU prices on this site, and there is a reason for that. A published range is either so wide that it tells a homeowner nothing, or narrow enough to be wrong for most parcels. What is genuinely useful is understanding how the number is assembled — because once you can see the buckets, you can read your own bids, ask better questions and recognize which line items are real and which are placeholders.
This guide explains how we build an ADU estimate at American Reliable Construction & Remodeling, what changes the number in the San Fernando Valley specifically, and how to compare two ADU bids line by line.
The four cost buckets in every ADU estimate
Our written ADU estimates are itemized into four buckets. Every bid you receive, from any contractor, is some version of these — the difference is whether they are shown to you or hidden inside a lump sum.
- Site work. Everything that happens before and around the structure: demolition, clearing, grading, drainage, excavation, the foundation system, trenching for sewer, water, gas and electrical, hardscape restoration and equipment access. This bucket varies more between properties than any other, and it is where a low bid usually turns out to be incomplete.
- Structure. The shell: foundation and slab, framing, sheathing, roofing assembly, exterior cladding, windows and exterior doors, waterproofing and insulation. On a garage conversion, part of this bucket already exists — but only the part that is sound enough to keep.
- Systems. Electrical service and subpanel, circuits and lighting, plumbing supply and drain lines, gas where used, HVAC (ductless mini-splits are typical in ADUs), ventilation, Title 24 energy compliance items and fire sprinklers where required.
- Finishes. Drywall, interior doors and trim, flooring, tile, cabinetry, countertops, plumbing fixtures, appliances, paint and hardware. This is the bucket a homeowner controls most directly, and the one most responsible for two identical floor plans landing at different totals.
Design, engineering, permits and fees sit alongside those four as soft costs. They are real money and belong on the estimate as their own lines rather than being absorbed silently into a square-foot figure.
Detached vs. attached vs. garage conversion vs. JADU — what changes the cost
A detached ADU is a complete new building: new foundation, new shell, new roof, new utility runs across the yard. It carries the largest site-work and structure buckets, and it also gives the most freedom in layout, separation and privacy.
An attached ADU extends the existing house. It shares a wall and often taps existing services at a shorter distance, which can reduce trenching — but it introduces work on the existing structure: cutting into framing, matching the roofline, verifying the foundation at the connection and sometimes upgrading the electrical service for the combined load.
A garage conversion reuses an existing footprint. Less structure normally means a smaller number, but garages in Los Angeles were built as unconditioned storage. Slabs are thin and sloped toward the door, perimeter footings are often shallow, ceiling heights get tight once an insulated floor assembly goes in, and detached garages sit at the back of the lot where sewer, water and power have the farthest to travel. A conversion is frequently the most economical path; it is not automatically the cheapest one.
A JADU is carved out of the existing house, generally with an efficiency kitchen and sometimes a shared bath. It touches the least new construction, but it consumes space you already live in and comes with its own occupancy and recordation requirements. State law lets many single-family parcels add both an ADU and a JADU; whether yours qualifies is a feasibility question, not a pricing one.
Site conditions that move the number in the Valley
On Valley parcels, these are the conditions that most often separate a straightforward ADU from an expensive one. We check every one of them during the feasibility visit, before an estimate is written.
- Hillside and fire-zone status. Sloped lots south of Ventura Boulevard bring grading, retaining, engineered foundations and hillside review. Parcels in a Very High Fire Hazard Severity Zone add wildland-urban interface construction standards affecting roofing, vents, glazing, siding and decks.
- Sewer route and distance. Depth and location of the sewer lateral decide whether the unit drains by gravity or needs an ejector pump, and how much trenching crosses driveway, patio or mature roots.
- Panel capacity. Many mid-century Valley homes still have their original service. A second dwelling with its own subpanel, mini-split and kitchen may require a service upgrade — a known line item when it is checked early, a mid-project surprise when it is not.
- Access for equipment. A narrow side yard, a gate that cannot pass a mini-excavator or a neighbor's wall inches from the property line changes how material and spoil move, and hand work costs more than machine work.
- Soil and foundation. Expansive soils, fill, high water conditions or a slope typically trigger a soils report and an engineered foundation rather than a conventional slab.
Permits, plan check and fees in Los Angeles
Who reviews the project depends on where the property sits. Sherman Oaks, Encino, Studio City, Van Nuys, North Hollywood, Woodland Hills and Tarzana are within the City of Los Angeles and go through LADBS. Burbank, Glendale and Calabasas each run their own building departments with their own submittal requirements, fee schedules and review queues — and Calabasas adds wildfire-zone standards and, in many neighborhoods, HOA architectural review.
Under current state law, ADUs under 750 square feet are generally exempt from local impact fees, with larger units charged proportionally to the primary dwelling. Plan check fees, permit fees, school fees where applicable and utility connection charges are separate items. Because these provisions are amended regularly, treat this as current law that you should confirm with the department reviewing your parcel; we verify it for every project before an estimate is finalized.
The City of Los Angeles standard plan program offers pre-reviewed ADU designs that can shorten review when one fits the lot. The site-specific portion of the submittal still goes through plan check, so the benefit is time rather than the removal of the permit process.
Design and engineering
Before anything is built, an ADU needs a measured site plan, floor plans and elevations, structural calculations, a Title 24 energy report and, on many Valley parcels, a soils report. On hillside sites, the engineering scope grows: foundation design for slope, retaining, drainage and sometimes shoring.
These are the least visible dollars in the project and among the most valuable. A complete, coordinated set reduces plan-check corrections, and corrections are the most common reason an ADU timeline stretches. Design and engineering should appear as identified line items on your estimate — if they are missing from a bid, either they are excluded or the total is not final.
Finishes and appliances: how allowances work
Cabinetry, countertops, tile, flooring, plumbing fixtures, lighting and appliances span an enormous range. Where selections are not made yet, a professional estimate uses allowances: a stated budget per category, with the quantity and quality assumption written down.
An honest allowance says what it covers — for example, the square footage of tile, the linear footage of cabinetry and the grade assumed. A vague allowance is where bids drift apart, because the homeowner selects upward later and the difference arrives as a change order. When comparing bids, check whether the allowances are equivalent before you compare the totals.
A note on financing
Homeowners generally fund ADUs with savings, a home equity line of credit, a cash-out refinance, or a renovation loan that lends against the improved value. California has also operated a CalHFA ADU grant program for pre-development costs, and its availability and funding status have changed over time. We are contractors, not lenders or financial advisors — confirm current program status and terms with the agency or lender directly, and take financial advice from a qualified professional.
How to compare two ADU bids line by line
- Same scope? Confirm both bids assume the same unit type, square footage and number of bathrooms before comparing anything else.
- Is site work itemized? Trenching distance, foundation type, grading and any panel upgrade should be visible, not implied.
- Are soft costs included? Design, engineering, Title 24, soils report, plan check and permit fees either appear or are excluded.
- Are allowances comparable? Match category by category, with quantities and grades stated.
- Who pulls the permit? It should be the contractor, under the contractor's license, not the homeowner as owner-builder.
- How are unknowns handled? The proposal should describe how a discovered condition becomes a written, signed change order.
- What is excluded? A short exclusions list is a sign of a careful estimator; no exclusions list usually means the questions have not been asked.
The lowest total is often the smallest scope. Our guide to choosing a Valley general contractor covers license verification and the questions worth asking before you sign.
What American Reliable includes in a written ADU estimate
We start with a free feasibility visit: zoning and setbacks, hillside and fire-zone status, sewer location and depth, panel capacity, access, soil indicators and whether the existing garage is worth converting. Then you receive a written estimate itemized into site work, structure, systems and finishes, with design, engineering, plan check and permit responsibility identified, allowances stated with their assumptions, exclusions listed, and a phase-by-phase schedule from submittal to certificate of occupancy. Permits and inspections are handled under CSLB #1155602. Warranty available. Call for details.
Local starting points: ADU construction in Sherman Oaks, Woodland Hills and Calabasas. If the goal is more space in the main house rather than a separate unit, compare it with room additions. To schedule a feasibility visit, call (877) 702-6180 or request a free in-home estimate.