City of Industry ADU Construction — 91744 / 91746
City of Industry ADUs are almost always built for multi-generational housing — adult children moving back home, aging parents moving in from the corridor or from out-of-state, married kids in the unit while they save for a down payment. The residential pocket inside 91744 and 91746 carries plenty of 5,500 to 8,500 square foot lots zoned for ADU under the LA County ordinance, which lets you build up to 1,200 square feet detached or up to 50 percent of the primary home for attached. NP Line Design has been doing architectural work in LA since 2016 and holding a CSLB General B since 2023, with 200+ LA-region builds. City of Industry ADU scope runs $168,000 to $300,000. Tier one — 480 to 600 square foot one-bedroom detached with a slab-on-grade foundation, stucco exterior, basic finish, and code-minimum efficiency — lands at $168,000 to $215,000. Tier two — 750 to 900 square foot two-bedroom with full kitchen, separated bath, and mid-grade finish — lands at $225,000 to $268,000. Tier three — 1,000 to 1,200 square foot two-bedroom with high finish, separated laundry, and a small patio — lands at $278,000 to $300,000. Bilingual project management. 24/7 at 818-605-1388.
City of Industry ADU Pricing 2026 — Three Tiers
Tier one is the 480 to 600 square foot one-bedroom detached ADU on a slab-on-grade — open kitchen and living, single bedroom, full bath, in-unit stacked laundry, stucco exterior, composition shingle roof, and code-minimum efficiency. Lands at $168,000 to $215,000. Tier two is the 750 to 900 square foot two-bedroom with a separated full kitchen, separated full bath, mid-grade finish package including quartz counters and engineered hardwood, and an upgrade to fiber-cement siding on at least one elevation. Lands at $225,000 to $268,000. Tier three is the 1,000 to 1,200 square foot two-bedroom with high-finish package — custom inset cabinetry, separated laundry room with storage, separated dining area, upgraded electrical for ADU multi-gen high-use, and a small concrete patio with covered overhang. Lands at $278,000 to $300,000. Each tier is line-item bid in English or Spanish with cut sheets, code references, and a clear utility-tie-in budget.The 91744 Multi-Generational ADU Use Case
Every City of Industry ADU we have built since 2024 has been programmed for multi-generational housing, not for short-term rental and not for rental-income investment. The use case shapes every design decision. The ADU is connected to the primary home by a covered walkway or a short concrete path that the grandmother can walk in slippers. The kitchen in the ADU is sized for daily cooking, not for occasional guest use — full 30-inch range, full-size refrigerator, real pantry. The bath is sized for aging-in-place — 36-inch entry door, curbless walk-in shower with bench, grab-bar blocking in the walls. The bedroom has a closet sized for a full wardrobe, not a guest-room closet. The HVAC is on its own zone so the grandmother can run her side warmer than the parents prefer. The design hours we spend up front are about translating the family conversation into a built environment, and the bilingual project management makes that conversation work. The cash-bid corridor competition does not do this design work.LA County ADU Code + The Utility Tie-In Reality
City of Industry ADUs route through LA County Building and Safety on EPIC-LA. The 2025 state ADU rules let you build up to 1,200 square feet detached or 50 percent of primary attached, with reduced setbacks and no owner-occupancy requirement. Plan check runs 14 to 28 days on a typical detached ADU. The real budget question on a 91744 corridor ADU is the utility tie-in — water tap, sewer connection, electrical sub-panel from the primary, gas line if applicable. Most 91744 tract homes have a 100-amp main service that cannot support an ADU on the same meter without an upgrade to 200 amps. The water service from the street to the primary is typically a three-quarter-inch line that needs to be upsized to one-inch if the ADU adds more than two fixtures. We carry the utility upgrades as clearly identified line items — typical 91744 ADU budget includes $14,000 to $22,000 in utility tie-ins depending on the parcel. The sewer connection cost varies most because the lateral location is unpredictable. We dig a test pit on every parcel before bidding.Why City of Industry Picks an Architect-GC for the ADU
The 91744 corridor ADU competition is a mix of cash-bid framing crews and modular vendors selling a prefab unit dropped on a slab. Both options have a place but neither fits a multi-generational program. The framing crew does not design the unit for aging-in-place or for the daily-cooking kitchen — they build what the homeowner draws on a napkin. The modular vendor sells a standard floor plan that does not match the family's actual use pattern. NP Line Design started as an architectural practice in 2016 — we draw the unit specifically for the family that will live in it. The CSLB General B since 2023 lets us also build it. The vertical integration matters because the same team that runs the family conversation about aging-in-place is the team that frames the curbless shower correctly and runs the bath branch circuits for the grab-bar blocking. 18 City of Industry corridor ADUs built since 2024. Bilingual on every job. Call 818-605-1388 — phone, text, web — 24/7.ADU Construction Questions Homeowners Ask About ADU Construction in Industry
What does a City of Industry ADU cost in 2026?
One-bedroom 480 to 600 square foot detached, $168,000 to $215,000. Two-bedroom 750 to 900 square foot with mid-grade finish, $225,000 to $268,000. Two-bedroom 1,000 to 1,200 with high finish and patio, $278,000 to $300,000.
How long does an ADU take to build?
Eight to ten months for a one-bedroom detached scope including permits, plan check, construction, and final inspection. Ten to twelve months for the two-bedroom mid-grade. Twelve to fourteen for the high-finish tier-three.
Do you build for short-term rental income?
Almost all our City of Industry ADU work has been multi-generational family housing, not rental income. We can design for rental use, but the design priorities — sound separation, durability, lower-maintenance finishes — are different from the multi-gen program.
What is the maximum ADU size allowed?
1,200 square feet for a detached ADU under current state law. Up to 50 percent of the primary home for an attached ADU. Most 91744 lots accommodate the full 1,200 square feet without a setback variance.
Do I need to upgrade my main electrical service?
Yes for most 91744 tract homes. Original 100-amp service will not support an ADU. We upgrade to 200 amps as a standard line item, around $4,800 to $6,400 with the meter coordination.
Will the ADU reassess my property tax?
Yes. New square footage from an ADU triggers a partial reassessment on the new value added, not on the existing home. Your existing Prop 13 base is preserved on the original home. Documentation provided for your accountant.
Can the ADU be designed for an aging parent?
Yes. Standard design priority on most of our City of Industry corridor builds. 36-inch doors, curbless walk-in shower with bench, grab-bar blocking in the walls, single-floor plan, and HVAC on its own zone.
What is the CSLB license?
CSLB General Building B-1, active since 2023. NP Line Design did architectural work in LA from 2016 forward. License covers all trades on an ADU build including structural, foundation, plumbing, electrical, mechanical, and finish.
Free On-Site ADU Construction Walkthrough in Industry
Book your City of Industry ADU walk-through. Call or text 818-605-1388. Chat at nplinedesign.com. Bilingual. 24/7.
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