A free site visit, a check of what your lot allows and a written, line-item price.
Get your free estimateFast, Reliable Home Addition Contractor Across Altadena
Most homeowners in Altadena who call us aren’t sure whether they need a detached ADU, a garage conversion, or a second-story addition. The first thing we do is walk the property, measure the lot, and check what unincorporated Los Angeles County will actually allow. A full second-story addition in Altadena typically runs $220,000 to $410,000 once structural retrofit, permits, and finishes are included. A garage conversion usually lands between $95,000 and $185,000 depending on electrical service, shear walls, and whether the slab can be reused. Call Miles Hartwell and the Sutton ADU Builders team at (472) 248-8213 to schedule a free estimate. We’ll give you a written price before any tool is lifted.
Why Sutton ADU Builders Is Altadena’s Preferred Home Addition Contractor Company
Altadena homeowners ask us different questions than people in newer housing tracts. They ask about balloon framing, ungrouted brick foundations, setback rules for hillside lots, and whether a crane can get down a narrow foothill lane. Those questions come from living in homes built between 1920 and 1970. Our crew knows these houses because we’ve worked on enough of them to recognize the patterns. When we open a ceiling off Lake Avenue and see true 2×4 balloon studs running from sill to eave, we already know what the foundation looks like before we look at it.
Every homeowner gets the same standard. We send you the name and photo of each technician before they arrive. They come in a clean, marked uniform and show a photo ID badge at the door. The written price you approve is the price you pay. If something fails within a year, the 365-Day Done Right Promise covers the fix at no cost, including a free second visit. That’s the Threshold Standard, and it applies to every project in Altadena, whether it’s a bump-out on a 1920s Craftsman or a full detached ADU behind a mid-century ranch.
Miles Hartwell runs this crew with one rule: no one shows up at your door whose name you didn’t already know. That matters when you’re home alone with young kids, or when you’re older and want to see a badge before you open the door. It’s why homeowners in Altadena’s quieter pockets north of Woodbury choose us over builders who send an unfamiliar sub on day one. Scheduling and dispatch are coordinated from our Los Angeles office, and crews serve Altadena locally.
Second Story Addition Contractor in Altadena
A Second Story Addition Contractor in Altadena has to solve a structural problem before any framing begins. Most of the single-story homes in this unincorporated foothill community sit on ungrouted brick or stone perimeter foundations with no continuous footing. Adding a second story means transferring hundreds of thousands of pounds through walls that were built as balloon frames, not platform frames. Our crew was called to a 1920s Craftsman bungalow just off Lake Avenue where the owner wanted a second-story addition over the existing back bedroom. The moment we opened the ceiling, the original balloon-frame studs were visible and the foundation was an ungrouted brick perimeter with no continuous footing. Before we could add any square footage upstairs, our tech had to design and install a steel moment frame and new grade beams to transfer the load. That structural retrofit alone shifted the budget by roughly 18%, but it allowed the final second-story addition to pass county inspection without a single change order on the framing package.
The structural retrofit comes first
Homeowners sometimes assume you can stack a new floor on top of an old bungalow the way you’d stack a deck. You cannot. In Altadena, the cost driver on second-story work is often not the lumber package or the roofing. It’s the steel moment frames, grade beams, and shear wall upgrades needed to tie the new load path to the ground. A typical second-story addition here runs $220,000 to $410,000. The structural portion alone often lands between $40,000 and $80,000. That’s not a line item you want discovered halfway through demolition.
Plan review is slower in unincorporated county land
Altadena falls under Los Angeles County building jurisdiction, not City of Pasadena. That changes the plan review process. County reviewers apply the same California Residential Code, but the queue and the fire-zone overlays for properties near Eaton Canyon add review steps. If your home is in a fire hazard severity zone, the county will want modified fire-resistant materials, which affects siding and roof choices on a second story. We account for this before you sign anything.
Garage Addition Contractors in Altadena
Garage Addition Contractors in Altadena see the same mistake repeated on nearly every older property: the homeowner prices the job as a finish-out, but the county requires a structural upgrade the original detached garage was never built to carry. A detached garage from the 1940s or 1950s typically has a four-inch slab without rebar, no shear walls, and an electrical service that cannot support a living space. In unincorporated Los Angeles County, converting that garage into an ADU or attached addition usually requires a separate electrical service upgrade, new shear walls, and a foundation-to-framing connection. A realistic Altadena garage conversion runs $95,000 to $185,000.
When the slab is reusable and when it is not
A garage slab can sometimes be reused if it’s thick enough and if the county accepts it as a foundation. Many older Altadena garage slabs were poured unreinforced, which means they crack under lateral loads. The county will want an engineered connection between the framing and the slab, often a new perimeter footing poured inside the existing shell. That work alone can add $12,000 to $25,000. If the slab has settled or shows deep cracking, the more honest path is a full rebuild, which moves the project into the $150,000 to $185,000 range.
Electrical service is the quiet budget killer
A detached garage on a 60-amp subpanel won’t support a kitchenette, a mini-split, and lighting. The county typically requires a 200-amp main panel if you’re adding a living unit. In an older Altadena home, that means a service upgrade at the main house plus a trenched feeder to the garage. Expect $4,000 to $8,000 for the panel and another $3,000 to $6,000 for trenching, depending on distance and whether the path crosses driveway concrete or tree roots. We put this in the written price before the job starts, not as a change order later.
Trusted Brands We Service in Altadena
We work directly with Abodu, Cover, and Dvele on prefab and panelized ADU packages, and we stock the common connection hardware and structural brackets those systems require on local Altadena jobs. That matters on a hillside lane where a prefab module has a narrow delivery window. If a bracket is missing, we don’t wait a week for parts. For customers weighing a prefab unit against a site-built garage conversion, Home Addition Contractor guidance includes an honest read on which product line fits the lot. Miles Hartwell knows these product lines well enough to tell you when a prefab approach saves money and when it fights the site. Steep driveways and protected oak canopies near the foothills make that conversation specific, not generic.
Common Home Addition Contractor Problems We See in Altadena Homes
- Balloon framing meets ungrouted masonry. Nearly every 1920s bungalow we inspect has stud bays that run from foundation to roofline with no fire blocking. Adding a second story to this type of frame requires a load transfer system before any new lumber goes up, and skipping it is the most expensive mistake we see corrected after demolition begins.
- Prefab units that cannot reach the pad. A crane or flatbed on a narrow, unimproved foothill lane in the unincorporated county sometimes triggers a private road improvement permit. We’ve seen homeowners buy an Abodu or Cover unit before checking whether the delivery truck can physically turn onto the property. Check the path first, then buy the unit.
- Fire-zone review caught late. Homes near the Eaton Canyon and Kinneloa fire zones fall under defensible space and fire-resistant material requirements. The county applies these during plan review, and they change siding, roofing, and venting specs. Discover that late and you’ll pay for new materials twice.
- Garage slab reuse assumed without testing. A garage conversion priced at finish-out cost, then the county rejects the slab for living space. That forces a new footing and sometimes a full rebuild of the garage shell. The difference is $40,000 to $90,000, and it shows up after you’ve already spent money on drawings.
Pricing for Home Addition Contractor in Altadena, CA
A room addition or bump-out in Altadena runs $80,000 to $160,000 for a single-story build on a home with a modern continuous footing. A second-story addition runs $220,000 to $410,000, with the structural retrofit typically accounting for $40,000 to $80,000 before framing, roofing, and finishes. Garage conversions run $95,000 to $185,000. Sunroom additions sit between $55,000 and $110,000. Bathroom additions start around $45,000 for a compact, code-compliant build and run upward from there. The two things that move the price most in this area: foundation condition and electrical service capacity on the existing home. The Threshold Standard means the written price we hand you before work starts is the price. Call (472) 248-8213 for a free estimate.
We Also Serve Cities Near Altadena
Our crews regularly work in Pasadena, La Canada Flintridge, San Marino, and Sierra Madre. The permitting authority changes at each city border, and so do the structural patterns. If you’re in one of those communities, the same written-price and photo-badge standards apply. For Altadena specifically, you’re reading the right page. Home Addition Contractor in Altadena work is what we do most weeks, and we know the county’s review quirks without having to look them up.
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 Home Addition Contractor in Altadena
Yes, it usually adds two to six weeks compared to an incorporated city like Pasadena. Plan review goes through Los Angeles County, and properties in fire hazard zones near Eaton Canyon or Kinneloa trigger additional review for fire-resistant materials. A typical addition takes 10 to 16 weeks from submittal to issued permit, plus build time. Call (472) 248-8213 and we’ll walk you through the exact sequence for your property.
A second-story addition on a 1920s or mid-century Altadena home usually requires a new continuous footing, grade beams, and a steel moment frame or engineered shear wall system to carry the added load off the original ungrouted brick or stone foundation. The old balloon framing typically cannot carry the new floor without reinforcement. Expect the structural package to cost $40,000 to $80,000. We include it in the written price before work starts.
Some detached garages in Altadena can convert, but the original slab, wall framing, and electrical service often fail county requirements for living space. If the slab is unreinforced or settled, rebuild. If it’s sound, you still need new shear walls, a foundation-to-framing connection, and usually a 200-amp service upgrade. A conversion runs $95,000 to $185,000. We’ll tell you after one site visit whether reuse is realistic.
A garage conversion typically takes 4 to 6 months from first drawings to final inspection. A second-story addition generally runs 7 to 12 months because of the structural retrofit and county fire-zone review. Materials availability and weather in the foothills can push framing weeks later in winter. We give you a written schedule with milestone dates, not a vague “about six months.”
On planned construction, the price should only change if you change the scope, or if demolition reveals a structural condition that was hidden behind walls or below grade. We minimize that by doing a structural pre-check before writing your price. If county reviewers demand a different fire-resistant material than originally specified, that’s a scope change from the county, and we document it in writing before proceeding. The written price is not an estimate; it’s a commitment.
Written by Miles Hartwell, Owner at Sutton ADU Builders, serving Altadena since founding the company in 2006.
