How Do I Know If My House Has Knob and Tube Wiring? San Jose Home Guide

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Quick Answer: To check if your San Jose home has knob and tube wiring: look in your attic and crawl space for single insulated wires (black cloth-covered) strung between ceramic or porcelain knobs (cylindrical insulators nailed to joists) and passing through ceramic tubes where they go through framing. Knob and tube wiring has no ground wire (two-conductor only) and was used from roughly 1880 through the 1940s. If your home was built before 1950, particularly in older San Jose neighborhoods like Naglee Park, Rose Garden, Willow Glen, and Shasta-Hanchett Park, it may have at least some original knob and tube wiring.

How to Identify Knob and Tube Wiring in a San Jose Home

Helpful Resources:

Visual Identifiers

Porcelain knobs: Small white or cream-colored cylindrical ceramic insulators nailed to the sides of floor joists and studs. Single wires are stapled or wrapped around them, keeping the wire away from flammable framing
Porcelain tubes: Short ceramic tubes inserted through holes drilled in framing members, allowing the wire to pass through wood without contact
Cloth-covered wire insulation: Original knob and tube wire insulation is rubber covered with black or gray braided cloth. It becomes brittle and cracked with age
No ground wire: The original knob and tube circuit has only two conductors — hot (black) and neutral (white). There is no bare copper ground wire
Two-slot outlets: If your home still has original two-slot outlets (not three-prong), this is evidence of ungrounded wiring from the knob and tube era

Where to Look

Attic (most common): The attic is where knob and tube wiring is most visible. Bring a flashlight and look along the tops of ceiling joists for ceramic knobs with single wires wrapped around or stapled to them
Crawl space: If your San Jose home has a raised foundation (common in pre-1960 homes), look along the undersides of floor joists in the crawl space
Electrical panel: If the panel has been updated, you may see both modern Romex cable (plastic-sheathed, 3 conductors) entering the panel AND some older cloth-covered wire — the combination indicates partial rewiring
Inside walls at outlets and switches: An electrician can pull the cover plate from an outlet or switch and look at the wiring — if it’s two-conductor cloth-covered wire with no ground, it’s knob and tube

Is Knob and Tube Wiring Dangerous?

Original knob and tube wiring is not inherently dangerous when undisturbed. The danger comes from: (1) Age — insulation becomes brittle and cracks, exposing bare wire; (2) Overloading — original circuits were designed for much lower electrical loads than modern households demand; (3) Improper modifications — previous owners or DIY work that spliced modern wiring into old knob and tube improperly; (4) Insulation contact — loose-fill attic insulation packed around knob and tube wiring traps heat and accelerates insulation deterioration.

Most home insurance companies in California will not insure a home with active knob and tube wiring, or charge a significant premium. Many lenders also require rewiring before loan approval. A complete rewire of a San Jose home costs $8,000–$25,000 depending on size and access.

Quartz Construction handles full home rewires as part of renovation projects throughout San Jose. Learn about full home renovation. CSLB #1003436 | Call (650) 749-7436.

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   Quartz Construction
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       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!
  
 
  
  
 
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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

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How Do I Know If My House Has Knob and Tube Wiring? San Jose Home Guide

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