A free site visit, a check of what your lot allows and a written, line-item price.
Get your free estimateADU Company in Altadena, CA
Adding an ADU in Altadena usually costs between $150,000 and $350,000 for a site-built unit, while prefab options from brands like Abodu and Dvele typically land between $120,000 and $300,000. What makes Altadena different from the flatlands below is the foothill terrain and the wildfire safety requirements that come with it. This page covers how those local conditions shape every project, what pricing actually looks like, and which neighborhoods we serve. Call (626) 658-3527 to talk through your property.
Why Altadena Homes Are Different
Altadena developed as a foothill community between the 1920s and 1960s, and that history shows up in the housing stock. Craftsman bungalows, Spanish Colonial Revivals, and mid-century ranches sit on generous lots, often with detached garages that seem ready for conversion. The catch is what’s underneath: many pre-1970 homes have aging foundations and original electrical panels that need evaluation before an ADU can be permitted. Altadena also sits in a Very High Fire Hazard Severity Zone, which means wildfire defensible-space rules and fire-resistant construction requirements apply here in ways they don’t across the border in Pasadena. And because so many lots are sloped, county hillside grading rules frequently enter the picture. A detached ADU is usually the most workable option given the backyard space, but the path to a permit is rarely as simple as the lot size suggests.
Wind-driven embers from Santa Ana conditions make material selection a real safety decision, not a style preference. Fire-resistant cladding, enclosed eaves, and tempered-glass windows are common requirements in the foothill neighborhoods. Homes with undocumented septic systems, which pop up regularly in the older pockets of Altadena, need evaluation before any permit application moves forward. Troy Eastman, our lead at Benson ADU Builders, starts every Altadena project by checking these site conditions first, because they dictate the budget more than any floor plan does.
Our Main Altadena Services
Altadena homeowners call us most often about two things: building a new detached ADU and adding square footage to an existing house. Here’s what each involves locally.
ADU Builders in Altadena
A detached ADU in Altadena almost always triggers hillside grading review, and in the foothill neighborhoods the fire-safety requirements shape everything from siding to window placement. We handle the full process: site evaluation, permit-ready plans, foundation work, and construction, including prefab options from Abodu, Cover, Dvele, and Mighty Buildings that can shorten on-site time significantly. ADU Builders in Altadena covers pricing, timelines, and what to expect from your specific lot.
Home Addition Contractor in Altadena
Home additions in Altadena often mean expanding a mid-century ranch or adding a primary suite to a Craftsman, and the existing foundation usually needs reinforcement before walls go up. We coordinate the structural engineering, permit package, and construction, keeping the original roofline intact where possible so the addition doesn’t look bolted on. Home Addition Contractor in Altadena walks through the process and the local cost drivers.
Room Addition Contractor in Altadena
Room additions here range from a single home office bump-out to a full primary suite over a garage. Older electrical panels and aging foundations on Altadena’s pre-1970 homes often need upgrades as part of the work, which we include in the written price before any construction starts. Room Addition Contractor in Altadena has the detailed numbers and a step-by-step walkthrough.
What happens when you call
- 1
A real person answersNo phone trees - you reach a local pro.
- 2
You get an upfront price rangeHonest numbers before anyone is dispatched.
- 3
A background-checked tech heads outLicensed & insured, dispatched right away.
- 4
You approve before work beginsNothing starts until you say go.
Brands We Service in Altadena
We build with prefab and materials brands homeowners can research independently, including Abodu, Cover, Dvele, and Mighty Buildings, plus James Hardie cladding. Learn more about our brands, what each offers, and which fits an Altadena lot best.
Pricing for ADU Company in Altadena, CA
| Service | Typical range in Altadena |
|---|---|
| Detached ADU (site-built) | $150,000 – $350,000 |
| Detached ADU (prefab) | $120,000 – $300,000 |
| Garage conversion ADU | $80,000 – $150,000 |
| JADU (attached junior ADU) | $60,000 – $120,000 |
| Home addition (site-built) | $200 – $400 per sq ft |
| Room addition (basic) | $50,000 – $120,000 |
| Primary suite addition | $100,000 – $200,000 |
| Foundation upgrade (typical Altadena lot) | $8,000 – $25,000 |
| Electrical panel replacement | $2,500 – $6,000 |
| Hillside grading review and shoring | $10,000 – $40,000 |
| Fire-resistant cladding upgrade | $15,000 – $35,000 |
| Septic system evaluation | $600 – $2,000 |
What pushes a price toward the top of these ranges in Altadena is almost always the lot: slope, fire-zone materials, foundation condition, and whether the home has a documented septic system. Every project we price includes a written quote before any work begins, and that number doesn’t move unless you change the scope.
Neighborhoods We Serve in Altadena
We work across Altadena, from the flats near Lake Avenue up into the foothill streets where fire-zone rules and hillside grading are everyday realities. Typical response for an estimate is within one to two business days, depending on site access.
- The Meadows
- Altadena Country Club area
- President Streets
- Channing Trail foothills
- La Vina
Service Area – Cities Near Altadena
Benson ADU Builders serves Altadena and the surrounding foothill and valley communities. Our crews work throughout Pasadena, CA, San Marino, CA, South Pasadena, CA, and San Gabriel, CA. Dispatch and scheduling are coordinated from our Los Angeles office, and we coordinate permits with the local jurisdictions on your behalf.
Serving Altadena, CA - Our Local Coverage Area
We’re based in the Altadena area and know this community well. Use the map below to see our service coverage - if you’re nearby, we can almost certainly help.
FAQs About ADU Company in Altadena
Most estimates are scheduled within one to two business days. Call (626) 658-3527 and a live person picks up, 24/7. We’ll ask a few questions about your lot and then lock a time.
Much of Altadena sits in a Very High Fire Hazard Severity Zone, which means fire-resistant siding, enclosed eaves, and defensible-space landscaping are often mandatory. We confirm your property’s exact status during the site evaluation, not after plans are drawn.
No. Your written price covers the scope we agree on, and it’s issued before any work begins. If you add something mid-project, we quote the change separately and you approve it before we proceed. The 365-Day Done Right Promise applies to every project in Altadena.
What happens when you call
- 1A real person answersNo phone trees - talk to a local adu pro.
- 2You get an upfront price rangeHonest numbers before anyone is dispatched. No surprises.
- 3We come out and measureLicensed & insured, at a time that suits you - the visit and the quote are both free.
- 4You get the price in writingLine-itemed, yours to keep, and nothing starts until you say go.
What Altadena Customers Say
"Garage conversion into a guest suite. I could see the permit status in the app, which made it painless."
- Rick F."Room addition off the kitchen. Framing, drywall, and paint all done well."
- Wade L."Fixed quote and clear change orders approved by text."
- Trina M.
