An attached ADU is built as an addition to the primary residence. It shares at least one wall and is structurally integrated into the existing home. It is neither an independent structure nor a simple conversion — it becomes part of the existing building envelope.
Attached ADU construction requires coordinated framing, fire-rated separation, and careful structural tie-ins. Because the new unit connects to the original structure, integration must be engineered and sequenced correctly.
Full permit management including structural tie-in documentation and fire-rated assembly details.
Efficient use of side or rear yard. Attached ADUs extend the existing structure rather than building a separate one. This preserves more open yard area compared to detached options. On narrower parcels common in Peninsula cities, this configuration maximizes buildable space while remaining compliant with setbacks.
Easier utility tie-ins. Because the addition connects directly to the main residence, plumbing, electrical, and gas lines may be shorter and more direct. Integration can simplify infrastructure routing, though capacity must still be evaluated before design is finalized.
Maintaining backyard space. For homeowners who want to preserve usable outdoor area, attaching the ADU to the existing home reduces site impact. This is especially relevant in tighter South Bay and Peninsula neighborhoods.
Extends the home rather than placing a second structure deeper into the yard.
Direct plumbing, electrical, and gas connections reduce infrastructure complexity.
Rooflines, siding, and proportions integrate into the existing façade.
Proximity with independence — shared structure, separate living spaces.
Attached ADUs must meet full residential code requirements. Integration with the primary structure increases complexity compared to standalone builds.
The shared wall must be designed as a compliant fire-rated assembly — specified drywall layers, sealed penetrations, and proper detailing at framing intersections. Structural reinforcement is often required where the new addition connects to the existing home.
Foundation systems must align, and load paths must be engineered so that roof and wall loads transfer correctly. Seismic compliance is critical across Northern California — shear walls, anchoring, and lateral bracing must be coordinated between old and new construction.
An attached ADU is not a room addition. It is a second dwelling integrated into an existing structure.
Structural tie-ins and fire-rated assemblies are engineered before permit submission.
Utility integration is often more direct than with detached units, but it still requires full evaluation. Electrical service must be reviewed to determine whether the existing panel can support additional load. In many cases, a dedicated subpanel is installed for the ADU.
Plumbing tie-ins require proper venting and slope. Sewer capacity must be confirmed. Gas line extensions must be sized appropriately and inspected.
Shared systems can reduce trenching and excavation. However, integration must be planned early to avoid rerouting during construction.
Attached ADUs require coordination between new construction and the existing home. We structure projects to address structural tie-ins, fire separation, and permitting before construction begins.
We verify setbacks, lot coverage, and structural attachment feasibility before drafting begins.Existing framing conditions are evaluated on-site.
Architectural design is coordinated with structural engineering to ensure proper tie-ins, load paths, and fire-rated assemblies.
Complete submissions include structural details, energy documentation, and clear delineation between primary residence and ADU.We manage all city communication and plan check responses.
Work proceeds in sequenced phases — foundation extension, framing integration, rough utilities, inspections, insulation, and finishes.
Attached ADUs tend to look straightforward on paper. The complexity shows up where new framing meets old framing. If tie-ins aren’t engineered properly, plan check comments follow. If fire-rated assemblies aren’t detailed clearly, inspections stall.
We sequence structural coordination first. Then utilities. Then permit submission. When integration is planned correctly, construction moves without surprises.
“Attached ADUs tend to look straightforward on paper. The complexity shows up where new framing meets old framing.”
— Dan Mendez, Owner
Setback rules, building footprint limits, and fire separation standards vary by city. We build attached ADUs across Peninsula, South Bay, and East Bay jurisdictions with familiarity in each.
Every property is different. We build every ADU type — evaluate which option fits your lot, zoning, and long-term goals.
A fully independent structure with its own foundation and utility connections. Best for properties with adequate yard space.
Detached ADU DetailsConvert an existing garage into permitted living space. Uses the existing footprint to reduce new construction scope.
Garage Conversion DetailsPermit coordination, plan check responses, and city communication managed from submission through final inspection.
Permitting ProcessBefore drawings are finalized, structural tie-ins and setback compliance must be verified. We review zoning, structural attachment points, and infrastructure capacity prior to permit submission.
Clear feasibility · Coordinated planning · Controlled execution
Serving Palo Alto · Mountain View · San Mateo
Walnut Creek · Redwood City · the Bay