Multi-generational | Attached ADU
Common in many US communities, the Raised Ranch presents a unique opportunity for integrating an attached ADU (Accessory Dwelling Unit) with minimal site disruption and interior layout disruption. Intelligent space planning can create flexible housing solutions for ranch homes with walk-out basements and suitable site conditions.
We developed two living units within one existing footprint in this case study. The homeowners are seeking to optimize their property’s use while considering future needs—specifically, the potential to provide housing for aging family members. Privacy and independence are critical, as is the option to rent the unit in the future.
The upper level remains unchanged, with three bedrooms and two full bathrooms. The lower level is reimagined as a separate one-bedroom, one-bathroom unit. Each unit also has a dedicated garage parking space.
Project Brief
Lot: As with any development, zoning clearance (by-right zoning and deal-breakers checklist) is critical to ensuring feasibility and a smooth timeline.
HOA: The Homeowners Association’s regulations must permit ADUs by right or have exclusions that make this possible.
Units: One additional unit is created, featuring a separate entry and kitchen, all within the same address. Utilities—such as electrical, water, sewer, and garbage—remain shared and are split between tenants.
Budget: What’s a reasonable budget? It should be comparable to the cost of retrofitting a lower-level unit while considering the additional value of dual living spaces.
Other: Flexibility and ease of integration are crucial, as the family wants the process to be as smooth as possible.
Range of Options
Detached ADU: A standalone structure separate from the main house, ideal for properties with more available space.
Attached ADU: As demonstrated in this case study, the ADU is integrated within the existing structure, offering efficient use of space and systems.
Flag-Lot + Home: Depending on the lot size and local zoning laws, creating a new lot behind the existing home may be an option.
The Fit: Attached Accessory Dwelling Unit
Systems Efficiency: Shared utilities (HVAC, water, and sewer) between the main home and the ADU provide cost-effective maintenance.
Footprint Efficiency: Utilizing the existing basement minimizes the need for additional land or new construction. Taking advantage of underutilized square footage, space previously allocated for "storage" or "flex" is transformed into an independent living space.
Site Optimization: The sloping lot and walk-out basement configuration allow each unit access to exterior spaces, ensuring privacy and outdoor areas for the main house and the ADU.
Outcomes
By rethinking their downsizing and retirement strategy, this family has created a flexible space that serves both current and future needs. The upper level continues to be their primary residence, while the accessory dwelling unit offers independent living quarters for a parent or the option to rent the space for additional income.
