The many forms and functions

At the luxury level, secondary structures take many shapes: a proper guest house (a full residence for visiting family and friends, offering privacy for both host and guest); staff quarters (accommodation for household staff, designed for discretion and separation); a home office or studio (separated from the main house for focus and work-life boundary); a wellness pavilion (gym, spa, yoga, or treatment space designed as a retreat); a pool house (from simple changing-and-lounge to a fully equipped secondary entertaining space); and multigenerational living (an independent suite for aging parents or adult children, balancing togetherness with autonomy).

Each function drives different design — a guest house prioritizes comfort and privacy, a wellness pavilion prioritizes light and calm, staff quarters prioritize discretion and separate access.

The regulatory reality

ADUs and secondary structures are heavily governed by local zoning, building codes, and — in many luxury enclaves — HOA and design-review rules, and the regulations vary enormously by jurisdiction. Some areas actively encourage ADUs (with streamlined approvals), while others restrict size, height, placement, separate utilities, rental use, or whether a kitchen is permitted (the presence of a kitchen often legally distinguishes a 'dwelling unit' from an accessory structure, with significant permitting implications).

Before designing, the feasibility question — what's allowed on your specific property — must be answered, and it's exactly the kind of thing an architect assesses early. The expensive mistake is designing a vision that local rules won't permit.

Design considerations for luxury secondary structures

The best secondary structures are designed in relationship to the main house and the site — coordinated in architecture and materials so they read as part of one estate rather than a bolted-on afterthought, positioned to balance connection and privacy, and often integrated with the landscape (a guest house across a courtyard, a pool house framing the pool, a wellness pavilion nestled in the garden).

Considerations include separate access and utilities (for privacy and independence), the relationship to the main house (visible and connected, or private and secluded), and future flexibility (a structure that can serve different purposes over time as needs change). Done well, a secondary structure adds enormous functionality, value, and livability to a luxury property; done as an afterthought, it detracts from the estate's coherence — which is why designing it as part of the whole, with the architect and landscape architect coordinating, produces the best result.