ADU Cost in Chula Vista (2026)

All-in cost by type and size

Every figure below is the calculator at its starting settings: custom design, a 1,600 sq ft house, flat ground, utilities within 50 ft, one shared meter. Design, reports, fees and contingency are inside. Below 750 sq ft west and east match, because only the impact fee differs by side.

Garage rows carry an $8,000 slab allowance because most garages have not been tested. If the slab proves sound, the two-car midpoint drops to about $145k; a slab that must be torn out and repoured pushes it to about $167k. Conversions and JADUs get wider ranges because old walls hide more surprises than a new foundation.

Detached units by finish level

The pieces inside $347k (750 sq ft, west side)

Choose a City Standard ADU Plan instead and the design line shrinks to a $4,000 allowance for fitting the plan to your lot, while the permit fee drops by $1,012. The 748 sq ft standard plan comes out near $320k, against $330k for a custom 749 sq ft unit.

The 750 sq ft impact-fee cliff

Chula Vista's Development and In-Lieu Fee bulletin (October 2025) exempts ADUs under 750 sq ft and every JADU from all development impact and in-lieu fees. From 750 sq ft, the unit is charged a slice of the single-family rate sized to the ADU's floor area against the main house's. Here are the rates that get sliced:

So adding one square foot, from 749 to 750, adds about $17,200 west of I-805 and about $27,000 east of it next to a 1,600 sq ft house. The midpoint jumps from $330k to $347k west and to $357k east. A bigger house softens the hit: next to a 2,400 sq ft home, a 760 sq ft east-side unit pays about a third of the east total instead of nearly half. Sewer basin fees (Poggi Canyon $265, Salt Creek and Wolf Canyon $1,955 per EDU) and Otay Ranch pedestrian bridge fees can also apply in parts of the east side.

Two cautions. The bulletin gives no ADU dollar amounts, so using the single-family rate as the base is our reading, and the City may apply it differently. And SnapADU reports that from January 1, 2027, SB 1117 counts only the square footage above 750; we have not confirmed that against the bill text. Note that two of the City Standard plans, at 748 and 749 sq ft, sit just under the line.

City permit fees

Chula Vista charges flat ADU permit fees, not a percentage of construction value. From Fee Bulletin 10-400 (September 2024):

Our sources disagree on the garage add-on ($158 per extra 400 sq ft in one summary, $211 per extra 300 sq ft under the remodel line in another), so confirm which line Development Services applies. Fees reset each year and a newer bulletin may exist. Builders quote "permits" much higher, $9,000 to $20,000 in one Chula Vista page, likely because they fold in impact, school and utility charges.

School fees: two districts, one check each

Most of Chula Vista sits in two school districts at once, so an ADU over 500 sq ft pays both.

Chula Vista Elementary takes payment through Facilitron; Sweetwater Union takes check, cashier's check or money order only. Inside San Ysidro High boundaries the Sweetwater rate is $2.10. The calculator charges the whole unit once it passes 500 sq ft.

Water: Otay or Sweetwater, plus the County Water Authority

Who supplies your water depends on where you live. Otay Water District serves eastern Chula Vista; Sweetwater Authority serves the west. There is no official boundary map in our research, so read your water bill rather than guessing by ZIP.

• SDCWA capacity charge: $6,683 in 2026 on any meter smaller than 1 inch, dropping to $5,617 on January 1, 2027. A 1 inch meter is $10,693 in 2026. It is charged only when you buy a new meter or upsize one.
• Local agency fees: neither Otay nor Sweetwater publishes its capacity and meter installation fees in a form we could retrieve, so the calculator leaves them out. Ask for a written quote before you choose a second meter.

An ADU that stays on the existing meter avoids the SDCWA charge. Sweetwater requires an application whenever an ADU is added, separate meter or not.

Sewer capacity

The City charges $4,793 per EDU (Fee Bulletin 12-100). A house counts as 1.00 EDU and an apartment as 0.79, but the bulletin does not say what an ADU counts as. The calculator uses the apartment factor, about $3,786, on new detached and attached units, and nothing for conversions inside existing space. If the City needs to build a new 4 inch lateral, its base charge is $9,160; when your own contractor builds it, the City tap-in is $600.

Utilities and site extras

Pile on a steep lot, a 100+ ft run, separate SDG&E and water meters and a new lateral, and a 750 sq ft unit climbs to about $453k west and $463k east. The San Diego Housing Commission's 2021 pilot saw one street trench quoted at over $100,000, so that owner kept shared utilities.

What drives the spread

• Size against fixed costs. A kitchen, a bathroom, utility tie-ins and permits cost nearly the same at 400 sq ft as at 1,200, so the all-in rate falls from about $580 to about $403 per sq ft.
• The 750 line. About $27,000 of impact fees for a 750 sq ft east-side unit, and more as the unit grows toward 1,200.
• Ground. Western lots are mostly flat. Canyon edges in Rancho del Rey and hillside streets in Eastlake and Rolling Hills Ranch can need deeper footings or retaining walls, which the calculator prices at 10% or 22% of construction.
• Distance. A unit at the back of a deep west-side lot needs longer trenches to the panel and sewer than one beside the garage.
• HOA review. East-side associations can add drawings, time and design conditions; see the Eastlake and Otay Ranch guide.

How builder prices compare

Add trenching, utilities and fees to a prefab price before comparing it with an all-in number. Three Escondido garage conversion bids gathered by Maxable ran $128,300 to $149,600.

Rent and return

Citywide averages hide a real east-west gap. HUD's Small Area FMRs for FY2027, as reported by a third-party mirror, put a two-bedroom at $2,590 in 91910 but $3,740 in 91913, $4,120 in 91914 and $3,810 in 91915. Those are voucher ceilings, not market rents, but RentCafe's neighborhood averages agree: Otay Ranch $3,199, Rancho del Rey $2,922, North Chula Vista $1,975. On the east side, the calculator's band is probably conservative.

Net is a year of rent less 5% vacancy, added property tax at $150 per sq ft assessed and about 1.1%, and 6% for upkeep and sewer. Loan payments, income tax and Mello-Roos are not in it. Rentals must run 30 days or more.

The City's ADU Loan Program

The City's deferred ADU loan, run by Housing and Homeless Services, tops out at $100,000 for a new ADU and $50,000 for a new JADU, with a separate $50,000 option for bringing an existing unit up to code. Per the program sheet, interest is 3% simple, and the balance is forgiven once you have rented the unit for 15 years under a regulatory agreement. Who qualifies: owner-occupants of at least a year who hold no other property and earn moderate income or less. The 2023 progress report showed $200,000 set aside for these loans, and we could not confirm the program is open in 2026, so ask before you count on it.

Property tax and Mello-Roos

Prop 13. Your house keeps its existing assessed value. Only the ADU is added, at its own new-construction value, which can bring a supplemental bill after completion. SnapADU sees San Diego assessors valuing finished ADUs at roughly $130–$165 a square foot, under their build cost. At the calculator's $150 and 1.1%, a 750 sq ft unit adds roughly $1,240 a year.

Mello-Roos. This is where Chula Vista differs from most of the county. Much of the east side pays special taxes to Community Facilities Districts, and an ADU can raise them:

• The newest districts tax ADUs directly. CFD 16M (El Dorado Ridge, 2024) charges $50 per ADU per year on top of $787 per home, at FY 23/24 rates.
• Older maintenance districts tax building square footage taken from permits. CFD 13M (Otay Ranch Village 2) charges $0.440 per sq ft of living space; if a 750 sq ft ADU were added at that rate, that is about $330 a year. Their documents are silent on ADUs, so whether yours gets added is a question for the City's CFD administrator.
• The Otay Water District improvement-district levy is $0.10 per $100 of assessed value, so it rises a little with the ADU's added value.

West of I-805, older neighborhoods generally have no Mello-Roos. The east-side guide lists the districts.

Ways to spend less

• Stay at 749 sq ft or under to skip impact fees, and at 500 or under to skip school fees too
• Build from a City Standard ADU Plan: lower design cost and a $1,012 smaller permit fee
• Turn an existing space into the unit: a garage conversion or a JADU pays no impact fees and no new sewer capacity charge
• Keep a detached unit close to the sewer line and panel, and share the water meter