Room Addition in San Jose
Need a room addition in San Jose? Custom Home builds additions at $350-$550 per square foot. Whether you need a second-story addition, ground-floor expansion, or bump-out, our two-phase process delivers 3D visualization and itemized pricing before construction starts.
How much does a home addition cost in San Jose?
Home additions in San Jose typically cost $350-$550 per square foot in 2026. A 500 sqft addition ranges from $175K to $275K. Custom Home's design phase locks in your exact cost before construction starts.
Why Expand Your San Jose Home
In San Jose’s competitive housing market, expanding your current home often makes more financial sense than buying larger. A well-planned addition adds both space and property value. Silicon Valley’s tech-driven economy supports strong demand for modern, energy-efficient residences.
Custom Home designs and builds home additions with the same two-phase process we use for custom homes. You see the complete addition in 3D and receive itemized pricing before construction begins.
Types of Home Additions We Build in San Jose
Second-Story Additions
Double your living space by building up rather than out. Second-story additions are ideal when lot coverage limits prevent ground-floor expansion. Custom Home’s structural engineers evaluate your existing foundation to determine what reinforcement is needed.
Ground-Floor Room Additions
Extend your home’s footprint with new bedrooms, family rooms, or home offices. Ground-floor additions integrate with your existing layout and maintain single-level living, which is especially valued in San Jose.
Bump-Outs and Extensions
Smaller expansions that make a significant difference: extend your kitchen, enlarge a bathroom, or add a sunroom. Bump-outs typically cost less and complete faster than full additions.
Structural Considerations for San Jose Additions
San Jose is located in a seismically active region, which means home additions must meet current seismic codes. Custom Home’s engineering team handles foundation evaluation, load-bearing wall modifications, and seismic design for every addition project. Whether you are adding a second story or expanding your footprint, structural engineering is included in our Phase 1 design process.
San Jose Home Addition Permits
San Jose’s Planning, Building and Code Enforcement department handles residential construction permits. The city offers online permit applications and plan check through the ePlan system. Standard custom home permits typically take 4-8 weeks for plan review. Pre-approved ADU plans can reduce permitting time to 2-3 weeks.
Custom Home manages the entire addition permitting process, including structural engineering review, plan submittal, and inspection coordination. Our experience with San Jose’s requirements helps keep the approval process on track.
Pricing for Home Addition in San Jose
Home addition costs in San Jose typically run $350-$550 per square foot, similar to new construction pricing. Second-story additions may cost more due to structural reinforcement requirements. Custom Home's Phase 1 design process locks in exact pricing before construction begins.
San Jose Permit Requirements
San Jose's Planning, Building and Code Enforcement department handles residential construction permits. The city offers online permit applications and plan check through the ePlan system. Standard custom home permits typically take 4-8 weeks for plan review. Pre-approved ADU plans can reduce permitting time to 2-3 weeks. Custom Home manages the full addition permitting process, including structural engineering review.
Home Addition in San Jose: FAQ
How much does a home addition cost in San Jose?
Home additions in San Jose typically cost $350-$550 per square foot. A 400 sqft room addition generally ranges from $140K to $220K. Second-story additions may cost more due to structural reinforcement. Custom Home locks in exact pricing during Phase 1.
How long does a home addition take in San Jose?
Home additions in San Jose typically take 6-12 months from design to completion. Second-story additions require 8-14 months due to additional structural work. Custom Home's design phase ensures construction runs efficiently and on schedule.
Can my San Jose home support a second-story addition?
Most homes can be structurally reinforced for a second story. Custom Home's engineering team evaluates your foundation and framing during Phase 1 to determine what modifications are needed and includes those costs in the itemized scope.