“Lior is very personable and has many decades of construction experience. We appreciated his sincere evaluation of our project.”
Ann AnterasianHouzz · April 2019
ADU construction · Altadena, CA
Altadena ADUs Under
the County's Rules
Deep foothill lots, craftsman-era houses, and an LA County permit desk that works nothing like LADBS. We design, permit, and build Altadena ADUs on the county's path. CSLB #972213.
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CSLB LicensedLicense #972213
5.0 on Houzz17 verified reviews
Family-OwnedLicensed since 2010
24-Hour ResponseFree in-home estimate
LA County DPWUnincorporated · in-house
Why Hillstar
What an Altadena ADU Project Gets From Hillstar
Between the county code path and the age of the housing stock, Altadena rewards builders who plan the whole picture before drawing it.
County Code Path, Not LADBS
Unincorporated Altadena permits through LA County Building & Safety with Regional Planning review — a different submittal, which we prepare natively.
Deep-Lot Advantage
Altadena parcels run deeper than most City of LA neighborhoods, which keeps detached new-builds on the table where tighter areas force conversions.
Century-Home Utilities Planned
Galvanized service, cast-iron waste, and small panels are common on the older stock; the ADU's utility plan prices their upgrades up front.
Oak & Foothill Review Ready
The county's oak-tree protections and hillside standards shape foothill envelopes. Arborist and grading review happen at design.
Fire-Rebuild Experience
Where Eaton Fire parcels are rebuilding, ADU work follows the county's rebuild guidance and WUI construction standards.
One Contract, One Crew
Feasibility, drawings, county corrections, construction, and inspections — a single accountable team.
Our process
An Altadena ADU, Step by Step
The county path, run in the right order.
1
Feasibility on the Lot
Zoning, setbacks, oak locations, hillside status, and utility capacity checked on-site before any promise is made.
2
Drawings for the County
Plans drawn to the LA County code path and filed with Building & Safety; corrections answered by us.
3
Construction
Foundation through finishes with our own crew, every county inspection scheduled and met.
4
Certificate & Warranty
Final sign-off, keys, and a written workmanship warranty on the finished unit.
Local conditions
Permits, Lots & What's Specific to Altadena
Altadena is the unincorporated kind of "in LA" — it's not the City of Los Angeles, it's not Pasadena, and it's not its own city. State ADU law applies, but the permit office, the design overlays, and the lot patterns here are all LA County, not LADBS, and look different from anything else in this region.
Permit jurisdiction
LA County issues every Altadena ADU permit — typically through the Department of Public Works (Building & Safety) and the Department of Regional Planning, with utility coordination through the local providers. LADBS does not. Pasadena does not. The LA City Standard ADU Plan Program is not accepted in unincorporated LA County; designs are drawn for the County code path. Plan check and inspections schedule directly with the County.
Lot & property patterns
Altadena's housing skews older — early-1900s craftsman, 1920s-'40s Spanish and English revivals, mid-century pockets — with deeper lots than most City of LA neighborhoods and a strong foothill character climbing toward the San Gabriels. Many properties carry plaster lath walls, original cast-iron drains, galvanized water service, and pre-1986 copper plumbing that may carry lead solder at the joints. Foothill parcels add hillside considerations.
Design overlays you'll see here
LA County's hillside development standards apply on classified hillside parcels — grading, height, and slope-stability provisions. Mature oaks are common across the foothill blocks; LA County's oak-tree ordinance applies where the build envelope sits inside a protected zone. Altadena foothill parcels classified inside California Fire Hazard Severity Zones trigger Chapter 7A WUI compliance where they apply (Class A roof, ignition-resistant siding, ember-resistant vents, defensible-space planning). The 2025 Eaton Fire reshaped portions of the area; fire-rebuild ADU work in Altadena follows the County's rebuild guidance and Chapter 7A WUI requirements where they apply.
Design examples
ADU Design Examples
Examples of ADU styles and layouts.
Reviews
Homeowners on Working With Hillstar
Verified Houzz reviews from Hillstar Construction clients.
“Lior is a fantastic general contractor. He has tremendous work ethic and strong attention to detail.”
J. GlaserHouzz · June 2017
“Hillstar's crew was courteous, prompt, and worked hard to make every detail exactly what we wanted.”
Hillstar ClientHouzz · Verified
5.0 · 17 verified reviews on Houzz
FAQ
Altadena ADU — FAQ
County permits, old-house utilities, foothill overlays, fire-rebuild context, and honest budgets.
Who permits an ADU in Altadena?
LA County — Altadena is unincorporated, so Building & Safety at the county's Public Works department issues the permit, with Regional Planning handling land-use review. LADBS has no role, and the City of LA's pre-approved Standard Plan Program doesn't apply here; plans are drawn for the county path from the start.
Can our older house support an ADU?
Nearly always, once the utility plan is honest. Altadena's craftsman and revival-era homes often run galvanized supply, cast-iron waste, and panels sized for another century. The ADU design scopes the panel upgrade and any service work first, so those costs appear in the written quote instead of mid-project.
What do the foothills add to an ADU project?
Three possible layers: the county's hillside development standards on classified parcels, oak-tree protections where a protected canopy overlaps the build envelope, and WUI construction requirements inside mapped fire-severity zones. The first site visit establishes which of the three actually touch your lot.
Does an ADU make sense on a fire-rebuild property?
Often, yes — some owners rebuild the main house and add a unit in the same effort. That work follows the county's rebuild guidance, and ignition-resistant construction applies where the parcel's zone requires it. We fold the ADU into the rebuild sequence rather than treating it as a separate project.
Detached, garage conversion, or JADU — how do we choose here?
Lot depth usually decides. Altadena's deeper parcels take detached units comfortably at the state's four-foot side and rear setbacks; a sound existing garage converts within its own footprint; and a JADU up to 500 square feet carves out of the main house when neither fits. Feasibility day answers it definitively.
What will an Altadena ADU cost?
Type, finish level, and utility scope drive it, so the honest number comes after the site visit — as an itemized written quote with the old-house contingencies visible. Rental rules are friendly: state law lets detached and attached ADUs rent without owner-occupancy; JADUs still require the owner on-site.
Also serving Altadena
Nearby ADU neighborhoods
Walk Your Altadena Lot With Us
Free feasibility visit — zoning, oaks, utilities, and a written plan for what your property supports.