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
Benson ADU Builders plans and builds accessory dwelling units, home additions, and room additions across Altadena, with written pricing before any work begins. Altadena’s mix of 1920s bungalows, mid-century ranch homes, and hillside properties means nearly every project involves a different foundation, lot slope, or setback situation. That’s exactly why we prepare a line-item proposal for each Altadena homeowner before a shovel turns. Call (903) 568-7222 and we’ll talk through your lot and your goals.
Why Altadena Homes Are Different
Altadena sits against the San Gabriel Mountains, and that geography shapes how we build here. Many homes north of Altadena Drive sit on sloped or terraced lots, which changes foundation work and drainage planning. A flat-lot ADU design that works near Lincoln Avenue may need retaining or stepped footings up near the Cheney Trail area. We plan for that from the first site walk, not after excavation starts.
The housing stock matters too. Altadena has a high concentration of homes built before 1940, and many still have original foundations that need evaluation before an addition can tie in. Electrical panels on older properties often need an upgrade to handle a new dwelling unit, and we include that scope in the written price so it doesn’t surprise you mid-project. The climate is another factor: hot, dry summers and winter rain mean we detail exterior cladding, flashing, and grading for both sun exposure and hillside runoff.
Our Main Altadena Services
Most Altadena homeowners call us for one of three projects: a detached or attached ADU, a full home addition, or a room addition. Each has its own dedicated Altadena page with pricing and timelines.
ADU Builders in Altadena
ADUs in Altadena range from garage conversions to new detached units, and lot slope plus access often dictates which route costs less. We build with prefab ADU brands like Abodu and Cover, which can shorten on-site construction considerably, and we also do full site-built units for irregular lots. Your Altadena property’s setback requirements and utility connections get mapped before we quote. Learn more on our ADU Builders in Altadena page.
Home Addition Contractor in Altadena
Home additions in Altadena usually mean expanding a kitchen, adding a primary suite, or extending the rear of a home to capture mountain views. Older homes here sometimes have foundation settling, so we inspect and correct for that before framing. Because many lots rise toward the back, drainage and retaining details are part of the written scope up front. See Home Addition Contractor in Altadena for pricing and process.
Room Addition Contractor in Altadena
A room addition is the most straightforward way to add square footage without a full remodel. In Altadena, we commonly build home offices, extra bedrooms, and sunrooms that open to the backyard. We coordinate with the city on setback and height rules for your specific block, and the price you approve is the price on the final invoice. Full details on our Room Addition Contractor in Altadena page.
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’re authorized to build with Abodu, Dvele, and Mighty Buildings, and we stock James Hardie cladding and common components for faster turnaround on Altadena jobs. That means you can research the product quality yourself before deciding. See our brands for the full lineup.
Pricing for ADU Company in Altadena, CA
Here are the ranges Altadena homeowners can expect, based on recent local projects. Every figure is confirmed in writing before we start.
| Service | Typical range in Altadena |
|---|---|
| Detached ADU (site-built, 400 sq ft) | $180,000 – $260,000 |
| Detached ADU (prefab, 400 sq ft) | $150,000 – $220,000 |
| Garage conversion ADU (400 sq ft) | $120,000 – $180,000 |
| JADU (attached, 400 sq ft) | $110,000 – $160,000 |
| Home addition (300 sq ft) | $90,000 – $140,000 |
| Home addition (500 sq ft) | $140,000 – $220,000 |
| Room addition (200 sq ft) | $60,000 – $95,000 |
| Room addition (400 sq ft) | $95,000 – $150,000 |
| Site prep, grading, and drainage work | $8,000 – $25,000 |
| Electrical panel upgrade | $3,500 – $7,500 |
Hillside lots, older foundations, and utility trenching are the three things that push Altadena prices toward the upper end of these ranges. You’ll never see a revised number after work begins unless you change the scope yourself.
Neighborhoods We Serve in Altadena
Our crews work throughout Altadena, from the flat streets near Lake Avenue up to the hillside homes off Fair Oaks and beyond. We know how each area’s terrain affects access and grading. Neighborhoods we frequently serve include:
- Altadena Town Center area
- North Altadena, near Loma Alta Drive
- The Meadows and Chaney Trail corridor
- President Streets area
- La Vina and surrounding hillside streets
Most Altadena projects are visited within a few business days of your call, and we quote a firm price from that visit.
Service Area – Cities Near Altadena
While this page focuses on Altadena, we also serve homeowners in Pasadena, CA, La Canada Flintridge, CA, San Marino, CA, and Sierra Madre, CA. Each of those communities has its own lot patterns and permit processes, and we handle both.
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
We typically schedule Altadena site walks within a few business days of your call. Since scheduling is coordinated from our Los Angeles office and crews serve Altadena locally, we can often accommodate evening or weekend walkthroughs for working homeowners.
Yes. Nearly every ADU, home addition, and room addition in Altadena requires a building permit, and hillside or slope work may trigger additional plan review. We prepare and submit the permit package as part of your project, and we don’t start work until it’s approved.
Some Altadena neighborhoods have HOAs, and their rules can affect placement, exterior finishes, and even unit size. We review your HOA’s guidelines during the quoting phase so your written price reflects what’s actually allowed on your lot.
Ready for a firm number on your Altadena ADU or addition? Call Benson ADU Builders at (903) 568-7222 for a free estimate, a written line-item price, and a project schedule before you commit to anything.
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
"Booked a consult online and met the project manager two days later. Weekly progress updates arrived by text with photos. ADU finished on schedule."
- Hannah W."Clean, quiet crew. They respected the neighbors, kept noise to working hours, and swept the driveway every evening."
- Hope C."Communication was the best part. I always knew what was happening that week without having to ask."
- Dolly N.
