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June 1, 2026
What Is the Design Development Phase? A Homeowner’s Guide
Design development (DD) is the second phase of architectural design, between schematic design and construction documents. It is where your project transforms from a concept into a fully resolved design. Here is what to expect.
What Happens in Design Development
In schematic design, you settled the basic layout and approach. In design development, every element gets refined and detailed:
- Floor plans are finalized with exact dimensions
- Exterior elevations are fully developed
- Windows and doors are selected and sized
- Exterior and interior materials are chosen
- Structural, mechanical, and electrical systems are coordinated
- Built-in elements like cabinetry are designed
What You Decide in This Phase
Design development is where you make the decisions that define how your home will look and feel: the kitchen layout, the bathroom fixtures, the exterior siding, the window style, the flooring. By the end of DD, the design is essentially complete.
Why This Phase Matters Most
Changes are inexpensive during design development and expensive after. Once construction documents begin and especially once construction starts, design changes cascade through structural, mechanical, and cost implications. Investing time and attention during DD pays off enormously.
How Long It Takes
For a custom home, design development typically takes 2 to 3 months. For a renovation or addition, 4 to 8 weeks. See our full overview of the 5 phases of architectural design.
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