A free site visit, a check of what your lot allows and a written, line-item price.
Get your free estimateTrusted Home Addition Contractor for San Jose Homeowners
A home addition in San Jose typically runs $180k to $450k for a ground-up project, depending on square footage, foundation work, and finish level. Most full additions take 4 to 8 months from permit to final inspection, and the permitting piece alone can stretch 6 to 12 weeks here in Santa Clara County. Getting a real number before you commit is the whole point of calling us at (669) 266-4319. We’re Lodgewick ADU San Jose, our Home Addition Contractor in San Jose, part of the Kingswell family of home-service companies since 2010, led by Russ Delmar, and we put every price, every arrival window, and every warranty term in writing before the first nail goes in.
Key Takeaways
- Written price first: You get a line-item quote before any work starts. No price changes at the door.
- 365-Day Done Right Promise: If something isn’t right within a year, we come back and make it right. That’s in writing.
- Real expertise: We work with prefab brands like Abodu, Plant Prefab, and Tuff Shed, plus James Hardie siding and trim.
- Local knowledge: We know San Jose’s permit process, soil conditions, and setback rules in neighborhoods like Willow Glen, Cambrian, and Almaden Valley.
- One phone number, always answered: Call (669) 266-4319 and a live person picks up, 24/7.
Sunroom Addition
A Sunroom Addition gives you a bright, glass-heavy living space attached to your home, usually without the full foundation and insulation requirements of a traditional addition. In San Jose, sunroom additions typically run $45k to $120k depending on glazing type, heating and cooling integration, and whether you’re building on an existing patio slab or pouring new footings. We handle permitting, framing, glazing, and finishing, and we’ll tell you upfront whether your sunroom needs to be counted as conditioned square footage by the City of San Jose. Our written quote covers everything, from the slab to the ceiling fan.
Three-Season vs. Four-Season Rooms
A three-season sunroom works great in San Jose’s mild climate but can get cold during December mornings. A four-season room is insulated and tied into your home’s HVAC, which adds cost but makes the space usable year-round. We’ll walk you through the real energy math before you choose.
Foundation and Glazing Choices
If you already have a patio slab, we can sometimes build on it and save thousands. If not, we’ll pour new footings to code. Glazing choices run from single-pane aluminum frames to double-pane low-E glass, and the difference shows up in your utility bill and comfort level.
Room Addition Contractor
A Room Addition Contractor builds new livable square footage onto your existing home, whether it’s a family room, home office, or expanded kitchen. In San Jose, a standard room addition runs $150k to $350k depending on size, structural work, and finishes. Lodgewick ADU San Jose handles the full scope: architectural drawings, structural engineering, permits, framing, rough-in, drywall, and finish work. You get one point of contact, one written price, and one guarantee. No subcontracted chaos and no surprise change orders.
Permit and Setback Navigation
San Jose’s setback rules vary by zoning district, and some older neighborhoods have non-conforming lots that complicate things. We’ve worked through these cases in areas like Rose Garden and Naglee Park. Your written quote includes the permit package and any variance work required.
Foundation Matching
Your new room’s foundation has to tie into the existing structure correctly, or you’ll get cracks and settling within a few years. We match footing depth and reinforcement to your existing slab or raised foundation. The Kingswell Way means we say the price before the work and leave the job site cleaner than we found it.
Second Story Addition Contractor
A Second Story Addition Contractor adds a full or partial upper level to your single-story home. This is typically the most expensive option because it means temporarily removing your roof, reinforcing the lower framing, and sometimes upgrading the foundation. In San Jose, second story additions run $250k to $500k or more depending on structural upgrades, stair placement, and whether you’re adding a full floor or a partial bump-out. Lodgewick ADU San Jose has the engineering partners and crews to handle this without cutting corners on the load path.
Structural Assessment First
Before you spend money on plans, we’ll check whether your existing walls and foundation can carry a second floor. Some 1950s and 1960s San Jose homes were built lighter than today’s code requires. If reinforcement is needed, we tell you the cost before any design work begins.
Living Through the Build
A second story addition means your roof comes off, which is disruptive. We sequence the work to minimize the time your home is exposed to weather, and we tarp and protect everything daily. The written guarantee covers the workmanship, and our crews are background-checked and uniformed, so you always know who’s on your property.
Garage Addition Contractors
Garage Addition Contractors build new garage space or convert and expand an existing garage into livable square footage. In San Jose, a new attached garage addition runs $80k to $180k, while a garage conversion to living space can run $120k to $250k depending on foundation insulation, window and door replacement, and utility rough-in. Lodgewick ADU San Jose, like a Home Addition Contractor in Milpitas, handles garage additions, garage conversions, and the hybrid cases where a homeowner wants parking plus a workshop or storage. We’ll match the roofline and exterior finish to your home so it looks like it was always there.
Attached vs. Detached Garages
An attached garage addition is simpler for utilities and access but must match your home’s exterior. A detached garage gives you more flexibility on size and placement. We’ll run the numbers on both options so you can decide based on real costs, not guesses.
Converting Existing Space
If you already have a garage but want livable square footage, a conversion is often faster and cheaper than building new. We handle insulation, drywall, flooring, electrical, and any required foundation work. Tuff Shed units can also be finished out as detached offices or workshops on lots with the right zoning.
Bathroom Addition Contractor
A Bathroom Addition Contractor adds a full or half bath to your home, either as part of a larger addition or as a standalone project within existing walls. In San Jose, a new bathroom addition runs $50k to $120k depending on plumbing distance, fixture quality, and whether you’re adding square footage or converting existing space. Lodgewick ADU San Jose pulls all plumbing and electrical permits, and we use licensed trades for every rough-in. Your written quote includes the shower valve, the vanity, the toilet, the tile, and the labor, so there’s no ambiguity about what’s covered.
Plumbing Distance Costs
The biggest cost driver in any bathroom addition is how far the new drain lines have to travel to reach your main sewer. Adding a bath on the opposite side of the house from the main stack costs more than one next to an existing bathroom. We’ll tell you the real number based on your home’s actual layout.
Ventilation and Waterproofing
A bathroom that isn’t vented properly will grow mold inside walls within a few years. We install exhaust fans that actually move air, and we waterproof shower surrounds before tile goes up. If the work fails within the 365-day guarantee period, we return free and make it right.
Bedroom Addition Contractor
A Bedroom Addition Contractor adds sleeping quarters to your home, either as a new ground-up room or by converting existing space like an office or den. In San Jose, a bedroom addition runs $60k to $150k for a standard 120 to 200 square foot room, depending on whether you’re building new or converting space and whether a closet and egress window are required. Egress windows are a code requirement for any room that will be used as a bedroom, and we handle that in the permit package. Lodgewick ADU San Jose builds bedrooms that meet California’s Building Code for light, ventilation, and emergency escape.
Egress Requirements
Any legal bedroom needs at least one egress window large enough for a firefighter in full gear to enter. If your conversion space doesn’t have one, we’ll cut and install it to code. This is the kind of detail that matters during a home sale or refinance appraisal.
Closet and Storage Design
A real bedroom needs storage. We build closets that match your home’s trim style and use the space efficiently, even in awkward rooflines or dormer additions. James Hardie siding and trim keep the exterior looking sharp while the interior stays functional.
Brands We Service
We work with Abodu prefab ADU units, which arrive as factory-built modules and get craned onto your San Jose lot in a single day. That speed changes the permitting and foundation math, and we handle both. If your lot suits a Tuff Shed structure finished out as an office or studio, we’ll run the conversion from bare shell to insulated, wired, and finished space with a written price before any work begins.
For traditional stick-built additions, we specify James Hardie siding and trim because it holds up to San Jose’s wet winters and dry summers without warping. And when a homeowner wants a high-performance prefab build, we can coordinate with Plant Prefab for wall panels that arrive cut, insulated, and ready to stand. Whether you have a specific brand in mind or want us to recommend the right approach for your lot and budget, we can help.
Signs You Need a Pro Right Now
- Permit rejection letter from the City of San Jose. If your addition plans were kicked back for code issues, you need someone who understands local zoning and building code. Resubmissions take time and money, and a contractor who knows the system can fix the problems the first time.
- Visible cracks in the existing foundation or walls. Before any addition goes up, the existing structure has to be sound. Cracks wider than a quarter-inch or doors that suddenly stick can mean foundation movement that has to be addressed before construction starts.
- Roof leaks or sagging in the area where you want to add on. Water damage or structural sag means the framing isn’t sound enough to support new loads. Adding square footage onto a compromised structure compounds the problem and can fail inspection.
- Mold or standing water in the proposed addition area. If you’re converting a garage or basement space and it has moisture problems, those have to be fixed before drywall goes up. Otherwise you’re sealing mold inside the walls.
- Electric panel is already maxed out. A new room or bathroom adds load to your electrical system. If your panel is full or old, you’ll need an upgrade before the addition passes inspection. We catch this early and include it in the written quote.
Our Process, Step by Step
- 1
Call and talk to a real person. Call (669) 266-4319 and you’ll get a live human being, not a bot. We’ll ask about your lot, your goal for the space, and your rough budget range. If it sounds like a fit, we schedule an on-site visit.
- 2
On-site walkthrough and measurements. We come to your San Jose home, measure, check the foundation and framing, and look at your electrical panel and sewer access. We’ll talk through what’s realistic for your lot and zoning. This visit is free.
- 3
Written line-item quote. Within a few days, you get a written price with every line item spelled out: permits, drawings, foundation, framing, rough-ins, finishes. No allowances or vague categories. The price we write is the price you pay.
- 4
Permits and construction. We pull all permits from the City of San Jose and manage inspections. During the build, you get defined arrival windows, a clean job site at the end of every day, and a single point of contact for questions. Our crews are background-checked and uniformed.
- 5
Final walkthrough and written guarantee. Before we call the job done, we walk the entire project with you and address any punch-list items immediately. Then we hand you the written 365-Day Done Right Promise. If something fails within a year, we come back free.
How Much Does Home Addition Contractor Cost in San Jose?
A typical home addition in San Jose runs $180k to $450k, with smaller projects like a sunroom or single bathroom landing between $45k and $150k and larger projects like a second story going $250k to $500k. The biggest cost drivers are square footage, site access, foundation type, and finish level. Homes on hillsides in areas like East Foothills or the east side of Almaden Valley often require more foundation work than flat lots in Willow Glen. Access matters too: if your backyard can’t accommodate equipment, crews may have to hand-carry materials, which adds labor cost.
The best way to avoid overpaying is to get a line-item written quote and compare it against other quotes line by line, not just the bottom number. A low bid often means allowances for fixtures or finishes that get upgraded later at your expense. Our free estimate includes all labor, materials, permits, and project management. Nothing is left as an estimate. Call (669) 266-4319 and we’ll give you a real number before you commit to anything.
Our Service Area Near San Jose
We serve homeowners throughout San Jose and the surrounding South Bay, including Willow Glen, Cambrian, Almaden Valley, Rose Garden, Naglee Park, Evergreen, and Alum Rock. We also take on projects in nearby cities like Fremont, Palo Alto, Milpitas, Los Gatos, Los Altos, and Union City. Our familiarity with each city’s permit office and local code quirks keeps projects moving. If you’re planning a home addition anywhere in the San Jose metro, we can help.
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.
Frequently Asked Questions About Home Addition Contractor in San Jose
A Home Addition Contractor Maintenance Checklist for San Jose Homeowners starts with a contractor who handles the design, permitting, construction, and finishing of new livable square footage attached to your existing home. That includes architectural drawings, structural engineering, foundation work, framing, electrical, plumbing, drywall, and finishes. Lodgewick ADU San Jose manages the entire process from the first measurement to the final inspection, with a written price and a written guarantee. Call (669) 266-4319 for a free estimate.
Most home additions take 4 to 8 months from permit submission to final inspection. The permitting phase alone takes 6 to 12 weeks in San Jose, depending on the complexity of your project and whether any zoning variances are required. Prefab options like Abodu units can cut construction time significantly. We’ll give you a realistic timeline in writing before work starts.
Home additions in San Jose typically run $180k to $450k for a full build, with smaller projects like sunrooms or single bathrooms in the $45k to $150k range. Your actual cost depends on square footage, foundation conditions, finish choices, and site access. Our written quotes are line-item, so you’ll see exactly where every dollar goes. Call (669) 266-4319 for an exact quote, estimates are free.
Yes, we work with Abodu prefab ADU units and Tuff Shed structures, from foundation and utility hookup to interior finishing. We also specify James Hardie siding and Plant Prefab panels for traditional build projects. If you have a specific brand in mind or want recommendations based on your lot and budget, call (669) 266-4319 and ask for Russ Delmar.
If you have a structural emergency, like a sagging roof or a foundation crack that’s actively worsening, call (669) 266-4319. A live person answers 24/7, and we can assess whether you need immediate shoring or if the issue can wait for a scheduled visit. Safety issues come first, and we’ll tell you honestly what you’re dealing with.
Every project comes with the 365-Day Done Right Promise in writing. If anything we built fails due to workmanship within one year, we return and fix it free of charge. The guarantee is handed to you before work begins, not after, and it’s in plain English with no fine-print exclusions for the things that matter. Call (669) 266-4319 to learn more.
Start by thinking about how you’ll use the space: a bedroom, a second bathroom, a home office, or a rental unit. Then gather any existing property records, like your parcel map, previous permit history, and any HOA rules if you have one. From there, call (669) 266-4319 and we’ll walk you through everything else, including budgeting, design, and what to expect during construction.
Schedule Your Home Addition Contractor Service in San Jose Today
If you’re ready to get a real number for your San Jose home addition, call (669) 266-4319 today. We’ll schedule a free on-site consultation, write you a line-item quote, and put the 365-Day Done Right Promise in your hands before any work starts. No pressure, no surprises. Just a straight answer from a live person, available 24/7.
Written by Russ Delmar, Owner at Lodgewick ADU San Jose, serving San Jose since 2010.
