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 San Jose
Adding a bathroom, bedroom, or full second story to a San Jose home usually starts with one question: what will this actually cost when the walls are open? The honest answer in this city is that homes built between 1950 and 1980 carry specific code triggers that newer construction doesn’t, and those triggers are where quotes move. We’re ADU Builders - San Jose, led by Russ Delmar, and we write those potential upgrade costs into your contract as allowances before we ever swing a hammer. If you’re planning an addition anywhere from Willow Glen to Evergreen, call (669) 266-4319 for a free estimate with real numbers.
Why Lodgewick ADU San Jose Is San Jose’s Preferred Home Addition Contractor Company
Russ Delmar and the Lodgewick team have walked through hundreds of San Jose ranch homes, and it’s the 1950s-to-1970s housing stock that separates this market from anywhere else in the Bay Area. These were solid houses for their time, but they were framed and wired before modern seismic and energy standards existed. That means a Home Addition Contractor who doesn’t plan for shear wall upgrades or panel replacements is going to hand you a change order mid-job, not a finished room. We price San Jose additions with written allowances up front, so when the inspector requires something, you already know the cost range.
Every Lodgewick project in San Jose operates under The Kingswell Guarantee. That’s a written price before work starts, a defined arrival window, a clean job site, and a written guarantee on every job. If something isn’t right within 365 days, we come back and fix it. No charge.
Homeowners in Almaden Valley, Willow Glen, and Evergreen tell us the same thing: the hardest part isn’t the construction, it’s finding a contractor who answers the phone and keeps the commitment. Our dispatch and scheduling are coordinated from our San Francisco Bay Area office, but crews live and work in San Jose. A live person answers every call, 24/7, at (669) 266-4319.
Bathroom Addition Contractor in San Jose
A bathroom addition in San Jose typically runs $45,000 to $85,000 when you’re adding a full bath with a shower or tub to an existing home. That range reflects what we regularly see in older ranch neighborhoods, where the original sewer lateral is often the wild card. A bathroom addition means new drain lines, and in Willow Glen specifically, we’ve found original 1950s clay sewer laterals that are too shallow to pass current code. Trenching and upsizing that line can add $4,000 to $9,000, and we write that allowance into your contract before work begins.
Sewer Lateral Reality Check
Before we quote a San Jose bathroom addition, we check the lateral depth and material wherever access allows. Clay pipe from the 1950s or 1960s frequently collapses or sits below modern slope requirements, and the city’s permit process requires that new plumbing tie into a code-compliant line. That’s not a surprise we want you to discover after demolition.
What the Permit Triggers
Adding a bathroom in a pre-1980 San Jose home will likely trigger updated GFCI protection, a dedicated circuit for the ventilation fan, and possibly a water heater upgrade if the existing unit can’t supply the new fixture load. We carry these as named line items with a dollar range, not a vague “TBD” that shows up later.
Bedroom Addition Contractor in San Jose
A bedroom addition in San Jose typically runs $35,000 to $65,000 for a single ground-floor room with a closet and egress window. That assumes the existing foundation is sound and the electrical panel has capacity. In Evergreen and the eastern foothills, many homes built in the 1960s still have 100-amp Zinsco or Federal Pacific panels, and a bedroom addition almost always triggers a panel replacement before final inspection. The panel swap itself runs $3,500 to $6,000, and we state that as an allowance from day one.
Foundation and Shear Wall Upgrades
San Jose sits in a high seismic zone, and any addition that ties into an existing home must meet current California Building Code for shear wall design. On a 1960s ranch with original 2×4 framing, that usually means adding hold-downs and OSB shear panels at the connection points. We price this work by the linear foot of connection, so you see exactly what the code is costing you.
Egress and Light Requirements
A legal bedroom in San Jose needs a window sized for egress, plus natural light and ventilation ratios that many original rooms don’t meet. If you’re converting an office or den into a bedroom, we verify the opening size and header condition first. Enlarging a window opening on a load-bearing wall adds $1,200 to $3,000 depending on the header span.
Trusted Brands We Service in San Jose
For additions that involve a prefab component or a specific material budget, we work hands-on with brands like Abodu, Plant Prefab, and Tuff Shed, and we use James Hardie siding on a majority of our Cover repair in San Jose exterior work. Hardie’s fiber cement stands up to the long dry summers and wet winters here without the expansion cracks you get with cheaper wood-composite products. Because we stock common trim, lap siding, and corner details locally for San Jose projects, material delays rarely hold up an exterior finish.
Common Home Addition Contractor Problems We See in San Jose Homes
- Undersized ceiling joists in 1950s-70s ranchers. Original 2×4 or 2×6 joists were never engineered for the spans created when a room opens up. We often specify engineered LVL replacement before any new roof or floor is tied in.
- Zinsco and Federal Pacific electrical panels. These panels are common in San Jose homes built before 1980, and inspectors will not sign off on an addition tied into one. The panel replacement is mandatory, and we price it in writing up front.
- Shallow or collapsed clay sewer laterals. Adding a bathroom without checking the lateral is a mistake. In Willow Glen and the Rose Garden area, we’ve seen original clay lines at 18 inches deep that must be re-trenched and upsized to meet code.
- Summer heat on exterior finishes. Evergreen and Almaden Valley additions that hit roofing or stucco work in July and August can lose productive hours to direct afternoon heat. We sequence exterior work for morning hours when temperatures allow, and we build that into the schedule honestly.
Pricing for Home Addition Contractor in San Jose, CA
Here’s what you can expect to pay in San Jose for common addition scopes: a simple bump-out of 100 to 150 square feet runs $28,000 to $45,000. A full bathroom addition runs $45,000 to $85,000. A ground-floor bedroom runs $35,000 to $65,000. A second-story addition over an existing footprint starts at $150,000 and can reach $300,000 depending on structural load paths and finish level. A sunroom or prefab-style addition using Tuff Shed or Plant Prefab components lands between $30,000 and $70,000. Every estimate is free, and every price we quote is written before work starts. Call (669) 266-4319 to schedule yours.
The reason quotes move in San Jose is almost always a code-triggered upgrade: shear walls, panel replacement, sewer upsizing, or engineered lumber. We price those as written allowances with specific dollar ranges, so you never get a “surprise” change order. You get a documented upgrade with a price you already approved.
We Also Serve Cities Near San Jose
Beyond San Jose proper, we handle additions in Milpitas, Santa Clara, Los Gatos, and Los Altos. The permitting processes differ slightly, especially between Santa Clara County and the incorporated cities, and our team knows which jurisdiction triggers which inspections. If you’re unsure whether your project falls under San Jose building code or a neighboring city’s rules, call (669) 266-4319 and we’ll tell you straight.
Serving San Jose, CA - Our Local Coverage Area
We’re based in the San Jose 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 San Jose
The increase happened because the inspector found something that was never on the original quote, usually undersized framing, an outdated panel, or a deteriorated shear wall. In San Jose’s 1950s-to-1970s housing stock, these discoveries are common, not rare. Lodgewick prevents this by building written allowances into every contract before work begins. The surprise is priced and approved before we touch it. Call (669) 266-4319 for a quote that accounts for what’s actually inside your walls.
No. Pre-approved ADU plans in San Jose simplify the permitting path, but they don’t change the structural requirements of your specific lot and existing foundation. A home addition that ties into an existing structure still needs a foundation evaluated for seismic loads, soil bearing, and connection to the original slab or perimeter footing. In Willow Glen, many homes sit on clay-heavy soil that requires deeper footings than the original 1950s construction provided. Call (669) 266-4319 and we’ll assess your specific foundation before quoting.
If your Evergreen home still has a 100-amp Zinsco, Federal Pacific, or original 1960s panel, then yes, the permit will almost certainly require a replacement. New additions in San Jose must tie into a panel that meets current code for capacity and breaker type, and inspectors will flag those older panels immediately. Budget $3,500 to $6,000 for the panel swap if yours is one of these. We state this as a line item with a fixed range before any work begins.
You can add the bedroom without trenching the sewer if the new second-story space does not introduce new plumbing fixtures and the existing lateral is in serviceable condition. But if you’re adding a bathroom up there, which most second-story additions include, you’ll need new drain lines that tie into the main lateral. In Almaden Valley, many laterals from the 1970s are clay and at the edge of their life. Have it camera-inspected before you commit to the floor plan. Call (669) 266-4319 to schedule that inspection as part of your free estimate.
San Jose’s Mediterranean climate allows year-round construction, and winter rain rarely stops foundation or framing work for more than a day or two at a time. The bigger schedule factor is summer heat. Roofing crews in Evergreen and Almaden Valley lose productive afternoon hours when temperatures push past 95 degrees, and stucco and exterior paint need cooler windows to cure properly. We plan exterior work for morning hours in July and August and write realistic timelines, not optimistic ones. Call (669) 266-4319 for a schedule that reflects actual San Jose conditions.
What Happens When We Open Your San Jose Wall
In Willow Glen, our crew opened the wall between a 1963 rancher’s kitchen and rear yard to add a 400 square foot family room. Immediately, the original 2×4 ceiling joists were visibly undersized for the new span. We paused, documented the damage with photos and measurements, and gave the homeowner a written change order for engineered LVL replacement and new hold-downs before touching anything else. That’s the difference between a code-triggered surprise and a planned upgrade. The homeowner knew the cost, approved it in writing, and the project moved forward without a single unexpected invoice.
Opening up an older San Jose home always turns up something. That’s not a problem if your Home Addition Contractor in San Jose treats the discovery as part of the job. We inspect first, write allowances into the contract, and price every surprise in writing before we touch it. Your quote should move for a reason you understand, not by surprise.
Get Your Written San Jose Addition Quote
Every Lodgewick ADU San Jose project starts with a free estimate that includes real dollar ranges for the work you want, plus written allowances for the upgrades your specific house will likely trigger. Russ Delmar and the team serve all of San Jose, from Willow Glen and the Rose Garden to Evergreen, Almaden Valley, and the East Side. The Kingswell Guarantee is simple: written price first, real arrival window, clean job site, written guarantee on every project. If it’s not done right within 365 days, we come back and make it right. Call (669) 266-4319 now to schedule your free estimate.
Written by Russ Delmar, Owner at Lodgewick ADU San Jose, serving San Jose homeowners with written-price additions and The Kingswell Guarantee.
