Second Story Addition Cost San Jose 2025 — Everything You Need to Know

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Categories: Architecture

Quick Answer: A second story addition in San Jose costs $350–$550 per square foot of new living space, making a full-floor 1,000 sq ft addition $350,000–$550,000. The wide cost range reflects foundation upgrades (if existing foundation can’t support the added weight), structural beam sizing, staircase placement, temporary relocation during construction, and finish level. A partial second story (master suite addition over an existing garage) costs $180,000–$320,000 for 400–600 sq ft.

Second Story Addition Cost Breakdown — San Jose 2025

Helpful Resources:

Cost Component	Percentage of Total	Notes
Structural engineering & foundation work	10–20%	Often the biggest surprise cost — older foundations frequently need reinforcement
Framing (walls, floor system, new roof)	15–25%	Floor joists, LVL beams, new roof structure are major components
Roofing (new roof over entire addition)	5–10%	Full tear-off and replacement of existing roof is usually needed
Windows & exterior	8–15%	New windows, stucco or siding to match existing
Mechanical (HVAC, plumbing, electrical)	15–25%	Extending existing systems or adding new mini-splits
Interior finishes	20–30%	Drywall, flooring, cabinetry, fixtures, trim
Permits & design	5–10%	Structural engineering, architecture, City of San Jose fees

Second Story Addition vs. Room Addition vs. ADU in San Jose

Second story addition: Best when the lot has no room for a horizontal addition; adds square footage above the existing footprint; disrupts the entire home during construction (most families temporarily relocate for 4–6 months)
First-floor room addition (bump-out): Less expensive per sq ft ($250–$400/sq ft); adds space horizontally; less disruptive but requires lot space and setback compliance
ADU (backyard): Separate structure; can generate rental income; less disruptive to main home; limited to 1,200 sq ft maximum

Structural Considerations for San Jose Second Story Additions

Many San Jose homes built in the 1950s–1970s were designed for single-story loads. Adding a second story requires a licensed structural engineer to evaluate the existing foundation, shear walls, and bearing walls. In the Bay Area’s seismic zone, second story additions must also meet current California Building Code lateral bracing requirements — meaning shear walls and hold-downs must be added or upgraded throughout the home, even in areas not being remodeled.

Frequently Asked Questions

Do I need to move out during a second story addition in San Jose? Most homeowners temporarily relocate during a second story addition, particularly during the roof removal and framing phase (typically 4–8 weeks). The home is open to the elements during this phase, with temporary weather protection (tarpaulins and temporary roofing) installed by the contractor. Some families stay in the home throughout, using sealed lower floors while the upper level is under construction — coordinate this expectation with your contractor before signing a contract.

How long does a second story addition take in San Jose? A typical second story addition in San Jose takes 10–18 months from project kickoff to move-in. The breakdown: 2–3 months for design and structural engineering, 4–7 months for permit review (San Jose’s full-plan-check review for structural projects typically takes 3–5 months), and 4–6 months for construction. Rush timelines are rarely possible due to San Jose’s permit processing queue.

Quartz Construction & Remodeling (CSLB #1003436) has completed second story additions throughout San Jose and the South Bay. Call (650) 749-7436 for a free feasibility assessment and preliminary cost estimate.

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What our clients say on Google

Verified reviews from our Google Business Profile. See all reviews on Google.

      
   Quartz Construction
   65 Google reviews 
  Write a review 
  
 
 
   
 
 
       Posted on Google  
   
   Perry Finch 
 
 
 
 Trustindex verifies that the original source of the review is Google. We’re so happy with the work Hila and her team did on our home addition. The new space flows beautifully with the existing structure, and the quality is clear in every finish. Finished on schedule and stress-free.
  
 
      Posted on Google  
   
   Joy Ruther 
 
 
 
 Trustindex verifies that the original source of the review is Google. Working with Ohad on our full home remodel was an incredible experience. He helped us through every decision and made sure everything turned out exactly how we envisioned. The team was easy to communicate with and super detail-focused. We still can’t believe how beautiful our home looks!
  
 
      Posted on Google  
   
   Ajay Mukhopadhyay 
 
 
 
 Trustindex verifies that the original source of the review is Google. We recently worked with Quartz Construction (Owner: Ohad) for a construction project to remodel our Bathroom
and we couldn’t be more pleased with the results. From start to finish, their team demonstrated professionalism, and exceptional craftsmanship.

They maintained clear communication throughout the project, kept us informed of progress and any potential changes, and delivered everything on time and within budget. Their quality of work is outstanding — every detail was handled with care and precision.

What stood out most was their commitment to customer satisfaction. They were responsive to our questions, respectful of our space, and ensured that the final outcome matched our vision perfectly.

If you're looking for a reliable, skilled, and trustworthy construction contractor, I wholeheartedly recommend Quartz Construction ( Ohad and his team) .They exceeded our expectations in every way.

Ajay
  
 
      Posted on Google  
   
   debbie curley 
 
 
 
 Trustindex verifies that the original source of the review is Google. I had a fantastic experience working with Quartz Construction And Remodeling. Ohad Maloul the owner was professional communicative and a pleasure to work with from start to finish. His team repaired and painted my backyard pergola and the quality of their work was truly excellent. They were always on time, friendly and responsive to any questions I had throughout the process. I appreciated the clear communication and attention to detail. I’m excited to work with Ohad and his team on future projects and highly recommend them to anyone looking for reliable, high-quality construction or remodeling services.
  
 
      Posted on Google  
   
   Harry Lewis 
 
 
 
 Trustindex verifies that the original source of the review is Google. Hila managed our balcony addition project with care and precision. The design complements our home perfectly, and the build quality is outstanding. She communicated every step and made the whole process easy. We’re thrilled with the result!
  
 
      Posted on Google  
   
   Qi Lei 
 
 
 
 Trustindex verifies that the original source of the review is Google. I had the chance to work with Ohad and his construction team on a recent home project, and I was really impressed. Ohad is professional, easy to communicate with, and genuinely cares about the quality of the work. The crew showed up on time, kept the work area clean, and finished the job on schedule. It’s hard to find contractors who are reliable and transparent these days, but Ohad delivered on everything he promised. Would definitely recommend if you’re looking for someone who takes pride in their work and keeps things straightforward.
  
 
      Posted on Google  
   
   Boris Tyron 
 
 
 
 Trustindex verifies that the original source of the review is Google. We’re so happy with the work Quartz Construction did on our backyard. Ohad’s team designed and built a gorgeous deck and patio that turned the area into a dream space. The quality and detail are fantastic. Highly recommend!
  
 
      Posted on Google  
   
   Gloria Collin 
 
 
 
 Trustindex verifies that the original source of the review is Google. Quartz Construction built the most beautiful pergola in our backyard, thanks to Ohad. He was easy to work with, listened to our needs, and delivered a structure that’s both stylish and durable. We now have a shaded space where we can relax and entertain guests.
  
 
      Posted on Google  
   
   Dustin Walsh 
 
 
 
 Trustindex verifies that the original source of the review is Google. They built a beautiful, durable pergola that fits our outdoor space perfectly. Hila paid close attention to both style and quality. We now have the perfect spot for lounging, gatherings, and enjoying every season.
  
 
      Posted on Google  
   
   Paul Wilins 
 
 
 
 Trustindex verifies that the original source of the review is Google. We feel incredibly lucky to have worked with Hila. She made the ADU process simple and stress-free, handling everything with care and professionalism. The final space is perfect—efficient, elegant, and exactly what we hoped for. Big thanks to her and the whole crew!
  
 
  
  
 
     Verified by Trustindex  Trustindex verified badge is the Universal Symbol of Trust. Only the greatest companies can get the verified badge who has a review score above 4.5, based on customer reviews over the past 12 months. Read more

Get a Free Estimate from Quartz Construction

Licensed General Contractor • CSLB Lic#1003436 • Serving San Jose, Santa Clara & Bay Area

Google Reviews — What Our Clients Say

      
   Quartz Construction
   65 Google reviews 
  Write a review 
  
 
 
   
 
 
       Posted on Google  
   
   Perry Finch 
 
 
 
 Trustindex verifies that the original source of the review is Google. We’re so happy with the work Hila and her team did on our home addition. The new space flows beautifully with the existing structure, and the quality is clear in every finish. Finished on schedule and stress-free.
  
 
      Posted on Google  
   
   Joy Ruther 
 
 
 
 Trustindex verifies that the original source of the review is Google. Working with Ohad on our full home remodel was an incredible experience. He helped us through every decision and made sure everything turned out exactly how we envisioned. The team was easy to communicate with and super detail-focused. We still can’t believe how beautiful our home looks!
  
 
      Posted on Google  
   
   Ajay Mukhopadhyay 
 
 
 
 Trustindex verifies that the original source of the review is Google. We recently worked with Quartz Construction (Owner: Ohad) for a construction project to remodel our Bathroom
and we couldn’t be more pleased with the results. From start to finish, their team demonstrated professionalism, and exceptional craftsmanship.

They maintained clear communication throughout the project, kept us informed of progress and any potential changes, and delivered everything on time and within budget. Their quality of work is outstanding — every detail was handled with care and precision.

What stood out most was their commitment to customer satisfaction. They were responsive to our questions, respectful of our space, and ensured that the final outcome matched our vision perfectly.

If you're looking for a reliable, skilled, and trustworthy construction contractor, I wholeheartedly recommend Quartz Construction ( Ohad and his team) .They exceeded our expectations in every way.

Ajay
  
 
      Posted on Google  
   
   debbie curley 
 
 
 
 Trustindex verifies that the original source of the review is Google. I had a fantastic experience working with Quartz Construction And Remodeling. Ohad Maloul the owner was professional communicative and a pleasure to work with from start to finish. His team repaired and painted my backyard pergola and the quality of their work was truly excellent. They were always on time, friendly and responsive to any questions I had throughout the process. I appreciated the clear communication and attention to detail. I’m excited to work with Ohad and his team on future projects and highly recommend them to anyone looking for reliable, high-quality construction or remodeling services.
  
 
      Posted on Google  
   
   Harry Lewis 
 
 
 
 Trustindex verifies that the original source of the review is Google. Hila managed our balcony addition project with care and precision. The design complements our home perfectly, and the build quality is outstanding. She communicated every step and made the whole process easy. We’re thrilled with the result!
  
 
      Posted on Google  
   
   Qi Lei 
 
 
 
 Trustindex verifies that the original source of the review is Google. I had the chance to work with Ohad and his construction team on a recent home project, and I was really impressed. Ohad is professional, easy to communicate with, and genuinely cares about the quality of the work. The crew showed up on time, kept the work area clean, and finished the job on schedule. It’s hard to find contractors who are reliable and transparent these days, but Ohad delivered on everything he promised. Would definitely recommend if you’re looking for someone who takes pride in their work and keeps things straightforward.
  
 
      Posted on Google  
   
   Boris Tyron 
 
 
 
 Trustindex verifies that the original source of the review is Google. We’re so happy with the work Quartz Construction did on our backyard. Ohad’s team designed and built a gorgeous deck and patio that turned the area into a dream space. The quality and detail are fantastic. Highly recommend!
  
 
      Posted on Google  
   
   Gloria Collin 
 
 
 
 Trustindex verifies that the original source of the review is Google. Quartz Construction built the most beautiful pergola in our backyard, thanks to Ohad. He was easy to work with, listened to our needs, and delivered a structure that’s both stylish and durable. We now have a shaded space where we can relax and entertain guests.
  
 
      Posted on Google  
   
   Dustin Walsh 
 
 
 
 Trustindex verifies that the original source of the review is Google. They built a beautiful, durable pergola that fits our outdoor space perfectly. Hila paid close attention to both style and quality. We now have the perfect spot for lounging, gatherings, and enjoying every season.
  
 
      Posted on Google  
   
   Paul Wilins 
 
 
 
 Trustindex verifies that the original source of the review is Google. We feel incredibly lucky to have worked with Hila. She made the ADU process simple and stress-free, handling everything with care and professionalism. The final space is perfect—efficient, elegant, and exactly what we hoped for. Big thanks to her and the whole crew!
  
 
  
  
 
     Verified by Trustindex  Trustindex verified badge is the Universal Symbol of Trust. Only the greatest companies can get the verified badge who has a review score above 4.5, based on customer reviews over the past 12 months. Read more

Get Your Free Estimate

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Phone: (650) 749-7436

Address: 1777 Hamilton Ave #1080, San Jose, CA 95125

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