When your home no longer fits your family's needs, an addition is often the smartest path forward. Instead of selling and moving, you can expand your existing space — adding square footage, bedrooms, or living areas that transform how your home works.
Based in San Mateo, we've helped homeowners throughout Hillsborough, Foster City, Belmont, Burlingame, and San Carlos expand their homes with second stories, room additions, master suite expansions, and bump-outs. We understand local zoning regulations, setback requirements, lot coverage limits, and the permitting process that governs residential additions.
What Makes a Great Addition
The best additions don't look like additions — they feel like they've always been part of the house. Our design team starts by understanding your home's existing architecture, rooflines, and character. Then we design an addition that integrates seamlessly with your current structure.
We also focus on how the new space will function. Whether you're adding a master suite, expanding your kitchen, or building a second story, we design for flow, natural light, and how you'll actually use the space every day.
Our Addition Services
- Second Story Additions: Adding a full second floor to expand bedrooms, bathrooms, or create dedicated spaces without consuming yard space.
- Room Additions: Single-room additions for master suites, home offices, playrooms, or in-law quarters.
- Bump-Outs: Smaller additions that expand kitchens, bathrooms, or living rooms by 3-8 feet.
- Master Suite Additions: Complete bedroom, bathroom, and walk-in closet suites added to your home.
- Kitchen Expansions: Extending kitchen footprints to accommodate islands, dining areas, or improved layouts.
- Sunrooms & Covered Patios: Enclosed or semi-enclosed spaces that extend your living area to the outdoors.
What to Expect
Additions require detailed planning, architectural drawings, structural engineering, and permits. We handle the entire process — from initial site assessment and design through permitting, construction, and final inspections.
Zoning regulations vary by neighborhood and lot size. We'll assess your property's setbacks, lot coverage, height limits, and FAR (floor area ratio) to determine what's feasible before we begin design work. This ensures we're designing something that can actually be built and permitted.
Timeline varies based on scope, but most projects take 4–8 months from design kickoff to completion. Second stories and larger additions may take longer due to structural complexity and permitting timelines.
Addition Costs on the Peninsula
Home addition costs in our area typically range from $300–$500+ per square foot depending on complexity, finishes, and site conditions. A 300-square-foot master suite addition generally falls in the $90,000–$150,000 range, while a full second story can exceed $300,000.
Bump-outs and smaller additions start around $50,000-$80,000 for basic expansions. These estimates include design, permitting, engineering, structural work, all finishes, and integration with existing systems.
We provide detailed cost breakdowns during the design phase so you can make informed decisions about scope and finishes that fit your budget.
Design Considerations
Our neighborhoods have distinct architectural character — from mid-century ranch homes in Foster City to Craftsman bungalows downtown and hillside estates in Hillsborough. We design additions that respect and enhance your home's existing style.
We also consider structural requirements. Adding a second story requires evaluating your home's existing foundation and framing. In some cases, foundation reinforcement or seismic upgrades may be necessary to support additional weight. We identify these requirements early in the design process so there are no surprises during construction.
Permitting & Zoning
The county and city have specific regulations governing residential additions:
- Setbacks: Minimum distances from property lines vary by zoning district.
- Lot Coverage: Maximum percentage of lot that can be covered by structures.
- Height Limits: Maximum building height varies by neighborhood.
- FAR (Floor Area Ratio): Limits total building square footage relative to lot size.
- Design Review: Some neighborhoods require design review board approval.
We handle all permitting and zoning research, applications, and approvals. You won't need to navigate the building department or attend planning meetings — we manage that process on your behalf.
Why Local Homeowners Choose Lussoro
We're a family-owned design-build firm, which means you work with the same team from concept through completion. No handoffs to project coordinators or subcontractors — we're accountable for every phase of your project.
We've built our reputation on transparency, craftsmanship, and follow-through. We understand that adding onto your home is disruptive, and we work to minimize that disruption while delivering a finished product that exceeds expectations.
Recent Projects
We recently completed a second-story addition for a homeowner in San Mateo. The project added three bedrooms, two bathrooms, and a laundry room — doubling the home's livable space without consuming any yard area. The new roofline matched the existing structure, and the siding, trim, and windows were selected to create a seamless integration.
Another project in Foster City involved a master suite addition with vaulted ceilings, a spa-inspired bathroom, and walk-in closet. The addition extended the rear of the home and opened onto a new covered patio, creating an indoor-outdoor living experience.
Areas We Serve
We're based in San Mateo and work with homeowners across the Peninsula and Bay Area, including:
- Hillsborough
- Foster City
- Belmont
- San Carlos
- Burlingame
- Redwood City
- Menlo Park
- Palo Alto
Ready to Expand Your Home?
The best way to understand what's possible for your property is to walk the site together. We offer free consultations where we visit your home, assess your lot, discuss your vision, and provide honest feedback about feasibility and budget. No obligation, no sales pitch — just a conversation about what could work.
Schedule your free consultation or call us at (925) 399-1238.