Altadena ADU Contractor Interview Sheet: 10 Questions Before Signing

Why Altadena ADU Projects Demand a Smarter Vetting Process

Since the 2025 fires, Altadena has seen a rise in contractors offering quick builds and cut-rate ADUs that promise more than they deliver — and homeowners who sign with the wrong builder often discover the gap between promise and permit only after money has changed hands. If you are planning an ADU here, the interview stage is where that outcome gets decided.

The stakes are unusually high in Altadena for three reasons. First, jurisdiction: because Altadena is unincorporated, your ADU is permitted through LA County's two-agency approval process — Regional Planning verifies zoning, while Building & Safety verifies building code. A contractor who doesn't know which agency handles what, or who has never pulled ADU permits in unincorporated areas, will cost you time you didn't budget for.

Second, the land itself. Hillside and slope lots require additional structural and engineering work, older homes often need electrical panel or utility upgrades, and fire-zone parcels can carry their own requirements — including possible Oak Tree Permits or historic-property standards that must be resolved before ADU approval, as local ADU guides note. Generic contractors routinely miss these until they surface mid-project.

Third, the hidden costs. Local builders report the surprises that derail budgets most often:

• Utility upgrades — typically $5,000–$20,000 for panels, sewer, water, and trenching work
• Soil conditions — $3,000–$15,000, especially on hillside lots
• Code upgrades — $5,000–$12,000 when older structures trigger current standards

These figures, reported by Southern California ADU cost research, are planning ranges, not quotes — but a competent contractor should be able to talk through all three categories before you sign, not after you excavate. As one post-fire Altadena ADU guide puts it, a legitimate professional will never pressure you into signing on the spot, and will be transparent about costs, timelines, and the permit process.

The payoff for getting vetting right is real. Most Altadena ADUs take 6–12 months from start to finish when the builder knows the county process, according to local ADU cost breakdowns. When the builder doesn't, the same project stalls in plan-check backlogs, utility coordination delays, and change orders. Contractor competence is the variable that separates those two outcomes.

That's why we built this interview sheet. At Altadena Custom Home Builder, we've seen what separates a smooth county-permitted ADU from a stalled one, and the ten questions below are designed to surface that difference in a single conversation — before you sign anything.

The First Competence Test: County Permitting Fluency

Before you discuss budgets or design preferences, ask one question that instantly separates county-fluent contractors from the rest: "Which two LA County agencies will approve my ADU plans?" Altadena sits in unincorporated Los Angeles County, so no city planning department touches your project — and a contractor who doesn't know that hasn't built here.

The two-agency process is your first pop quiz. According to Altadena Heritage's ADU guide, two agencies must approve your plans: Regional Planning verifies zoning conformance (setbacks, height), while the Department of Building & Safety verifies building code compliance. A competent contractor should also name the county's ADU ordinance — Ordinance 2020-0059 — and know that applications go through the EPIC-LA online portal, per the same guide.

Question 1: "Walk me through the county approval process for an ADU in Altadena." Listen for both agencies, the ordinance number, and EPIC-LA submittal. Vague answers about "the city" end the interview.

Question 2: "What timeline should I expect for permits?" State law requires a 60-day decision on complete ADU applications, and the county makes a completeness determination within 15 business days, with preapproved-plan detached ADUs decided within 30 days, according to local permitting research. But a post-fire Altadena ADU guide warns that county backlogs and plan check comments can still cause delays — an honest contractor says so rather than promising the 60-day mandate as a guarantee.

Question 3: "What size and setbacks am I entitled to?" California guarantees the right to build at least one 800 sq ft ADU with 4-foot side and rear setbacks, no minimum lot size, and height limits of 16 feet for detached units. A contractor who doesn't know your entitlements may design smaller — or larger — than the law allows.

Question 4: "What could trigger discretionary review on my lot?" This is where local expertise shows. A strong candidate flags these unprompted:

• An Oak Tree Permit, which must be secured before ADU approval if protected oaks sit on the parcel
• County historic-property standards — Altadena contains county landmarks and a pending historic district
• Fire-zone requirements, including parking rules for Very High Fire Hazard Severity Zone parcels

At Altadena Custom Home Builder, we treat permitting fluency as non-negotiable when vetting builders for ADUs and Eaton Fire rebuilds alike — the same county processes govern both. A contractor who stumbles on the basics here will stumble on your build.

Site Reality Checks: Hillside Lots, Older Homes, and Fire Zones

A contractor who quotes your ADU over the phone has already told you something important: they haven't looked at your land. In Altadena, where hillside lots, mid-century homes, and fire-zone parcels are the norm rather than the exception, the site itself often determines whether your budget survives construction. As one local cost guide puts it, "many ADU projects uncover additional costs once construction begins, especially in older homes."

Question 5: Will you evaluate the site and study utility capacity before quoting?

Hidden costs are the number one ADU pitfall. According to Southern California cost research, utility upgrades alone run $5,000–$20,000, soil conditions add $3,000–$15,000, and code upgrades can tack on another $5,000–$12,000. A serious contractor investigates these before committing to a number. That same research recommends a 20% contingency fund, while Altadena-specific guidance suggests 10–15% — either way, a contractor who dismisses contingency planning is waving a red flag.

Question 6: What hillside and slope-lot ADUs have you engineered?

Hillside versus flat lots significantly affect cost and require additional structural and engineering work, per local ADU cost analysis. Altadena's terrain makes this non-negotiable. Ask for:

• Specific hillside ADU projects completed in unincorporated LA County
• How they handled drainage, retaining structures, and foundation inspections
• Whether their quote includes a geotechnical or soils review
• References from slope-lot clients you can actually call

Older homes add another layer. Many Altadena houses need electrical panel upgrades, sewer or water line improvements, and utility trenching before an ADU can connect — costs that only surface during a physical site evaluation.

Question 7: How familiar are you with fire-zone rules and Eaton Fire rebuild contexts?

Much of Altadena sits in a Very High Fire Hazard Severity Zone, where parcels may still trigger a one-off-street-parking-space requirement unless an exemption applies, according to LA County ADU guidance. A contractor should know this without checking. Post-fire rebuilding also emphasizes fire-resistant materials and smarter site planning that considers future risks — not just minimum code compliance.

At Altadena Custom Home Builder, we treat the site walk as the foundation of the entire conversation. A free build consultation before you sign anything is the cheapest insurance you'll ever get on a hillside, fire-zone, or rebuild project.

The Money Conversation: Contingencies, Scope, and Red Flags

The last three questions in your interview sheet are where the money conversation happens — and where a vague answer can cost you tens of thousands of dollars mid-build. Hidden costs are the number-one ADU pitfall in Southern California, according to builder guidance on 2025 ADU costs and pitfalls, so this is the part of the interview you cannot rush.

Question 8: "What hidden costs should I expect on my lot?" A competent Altadena contractor will name them unprompted: utility trenching, electrical panel upgrades, drainage improvements, and structural reinforcement are all common line items on Altadena ADU projects, especially on hillside lots and older homes. Regionally, utility upgrades alone run $5,000–$20,000, soil conditions add $3,000–$15,000, and code upgrades add $5,000–$12,000. A contractor who says "that never comes up" hasn't built here.

Question 9: "What contingency should I budget?" Local builders commonly recommend 10–15% of the project budget for surprises, while some Southern California guidance goes as high as 20% — treat these as planning ranges, not quotes, since every lot differs. As one Altadena cost guide puts it, "Many ADU projects uncover additional costs once construction begins, especially in older homes," which is why online pricing should be used for planning, not as a final quote.

Question 10: "What's included in your scope?" Full-service ADU firms typically handle feasibility analysis, design-build, permit management, and utility coordination through turnkey delivery. Ask specifically about inspections — Altadena ADUs pass through foundation, framing, utilities, and final approval stages, and your contractor should manage all of them. Utility coordination matters most: the Urban Institute notes that utility approvals are often a major source of delay.

Your scope checklist should confirm:

• Permit management through LA County's two-agency process (Regional Planning and Building & Safety)
• Utility coordination and capacity studies before quoting
• Inspection attendance at foundation, framing, utilities, and final stages
• A written change-order process for anything discovered mid-build

Watch for pressure to sign. Post-fire Altadena has seen "a rise in contractors offering quick builds and cut-rate ADUs that promise more than they deliver," per post-2025 fire ADU guidance. The rule is simple: a legitimate professional will never pressure you into signing a contract on the spot, and they will be transparent about costs, timelines, and permit processes. If a "today-only" discount appears, walk away.

At Altadena Custom Home Builder, we advise homeowners to sleep on every contract — a free build consultation gives you a second opinion before any ADU, rebuild, or ground-up project goes to paper.

Your Next Step: Putting the Interview Sheet to Work

A printed interview sheet only works if you know what "good" sounds like — and if you verify the answers independently. Here's the full recap, followed by the three verification steps that separate a legitimate Altadena ADU builder from a smooth talker.

1. Which agencies approve my ADU plans?
2. Will you complete a site and utility evaluation before quoting?
3. How many permitted ADUs have you built in unincorporated LA County?
4. How do you handle hillside lots and older homes?
5. What's your experience with fire-zone and Eaton Fire rebuild sites?
6. Which discretionary permits might my lot trigger?
7. What hidden costs should I expect, and what contingency do you recommend?
8. Can I verify your license and insurance?
9. May I contact references from permitted ADUs?
10. What's your full scope — permits, utilities, coordination?

What a strong answer sounds like: For question one, a competent contractor instantly names both agencies — Regional Planning and Building & Safety — and can explain the 60-day county decision mandate without looking it up. For question seven, expect honesty about utility upgrades ($5,000–$20,000), soil conditions ($3,000–$15,000), and code upgrades ($5,000–$12,000), plus a contingency recommendation in the 10–20% range. A contractor who quotes a single flat number with no site visit is telling you something.

• Check the CSLB license. Look up the contractor's license number at cslb.ca.gov and confirm the classification, status, and bond. JMB Builders LLC (CSLB #1103479), for example, is an Altadena-based licensed general contractor whose ADU and Eaton Fire rebuild work is documented on its own site.
• Call references from permitted ADUs in unincorporated areas. Ask each reference whether the project passed final inspection on schedule and whether the final cost matched the estimate. Post-fire, Altadena has seen a rise in contractors offering quick builds and cut-rate ADUs that overpromise — references from actual county-permitted projects are your best filter.
• Confirm insurance directly. Request a current certificate of liability insurance and workers' compensation coverage from the insurer, not a photocopy from the contractor.

Before you sign, review the county's official ADU guidance — Altadena Heritage maintains links to Ordinance 2020-0059, the county's step-by-step ADU guide, and the Standard ADU Plans Program. Also note the CalHFA ADU grant, which provides up to $40,000 toward pre-development costs and non-recurring closing costs for eligible homeowners.

One more caution from the research: a legitimate professional will never pressure you into signing on the spot. With LA County homeowners completing a record 10,230 ADUs in 2025, good contractors have plenty of work — the ones rushing your signature are the ones to walk away from.

Ready to talk through your project? Altadena Custom Home Builder offers a free build consultation for ground-up custom homes, tear-down rebuilds, and Eaton Fire rebuilding — an Altadena field guide to help you plan with confidence.