Attached ADUs in San Jose

An attached ADU shares at least one wall with your existing house. It can be a bump-out off the back or side of the home, a conversion of attached space like a tuck-under garage or an oversized rear room, or a combination of both. The unit still needs its own entrance, kitchen, bathroom, and living area, which is what separates an attached dwelling unit from a bedroom addition.

We build all four ADU types in San Jose, and the attached version is the one we recommend most often on standard city lots. If you are still deciding which direction fits your property, our overview of what an ADU adds to a property is a good place to start.

The shared wall is where an attached ADU gets technical. Building code treats the connection between the primary residence and the accessory unit as a separation that has to perform, not just a partition.

• Fire separation. The common wall assembly, and often the floor or ceiling if the unit is stacked, needs a rated construction with the right drywall layers, framing details, and penetration sealing. Every plumbing and electrical hole through that wall has to be firestopped correctly.
• Sound insulation. Code minimums are one thing, livability is another. We routinely go past the minimum with staggered or resilient framing, insulation in the cavity, and careful detailing at outlets, because a rental that transmits every footstep is a rental with turnover.
• Utilities. Attached units can usually share the existing water and sewer laterals, but the panel is the common bottleneck. Older San Jose homes on 100-amp service often need a service upgrade before we add a second kitchen, laundry, and heat pump. We check that during the first site visit, not after framing.
• Independent access. The unit needs its own exterior door that does not route through the main house.

We are a licensed general contracting company based here in San Jose, owner-operated, and we take on fewer projects than a volume builder does so the work gets real attention. Becir is on the job, not just on the contract. Our portfolio runs from whole-house remodels in San Jose to projects in Los Altos and Portola Valley, and the attached ADU sits right in the middle of what we do best: cutting into an existing structure without damaging what is already there.

That last part matters more than most homeowners expect. Tying new framing into an existing roof, matching stucco or siding so the addition does not read as a bolt-on, and keeping the main house livable during construction are all execution problems. If your project is closer to a full expansion than a separate unit, our home addition services cover that path instead.

Every attached ADU starts with the lot, the existing structure, and what you want the unit to do. Send us the address and a rough idea of the plan and we will tell you honestly whether attached is the right format or whether you would be better served detached. Get in touch with our San Jose office and we will set up a site visit.