What should we review before designing an ADU or addition?
Start with the intended use, existing property and unanswered site questions. This checklist helps organize a feasibility conversation before investing in a detailed design.
Define the purpose of the extra space
Explain whether the new space is intended for family, guests, a home office or a separate residence. These goals can lead to different planning conversations, so do not treat an addition, conversion and detached dwelling as interchangeable. Write down the rooms, privacy, accessibility and storage you need, along with a rough project budget. Separate essential functions from preferences about size or appearance. A clear brief lets your design and construction team compare approaches before drawings become too detailed to change easily.
Gather records and identify unknown conditions
Collect existing plans, surveys and available records for the property. Label their dates and tell the team whether they reflect the home as it exists today. Note existing structures, trees, slopes, drainage concerns, site access and known utility information without guessing at hidden conditions. A detached structure, a garage conversion and an attached expansion raise different technical questions. Ask which site visits or specialist investigations would help clarify the unknowns, who will arrange them and how those findings could change the planning approach.
Have the appropriate team confirm the approval path
The property's jurisdiction and conditions matter. Ask your architect or other responsible design professional to confirm the current planning and building requirements that apply to the proposed work. Do not use a general online checklist as a determination that a specific property qualifies. Clarify who is responsible for submitting plans, responding to comments and coordinating any required specialist input. Keep assumptions separate from confirmed information in the project notes, and revisit the budget and schedule when an important assumption changes.
Consider the whole site budget
The usable room area is only part of the work. Depending on the actual design and conditions, the plan may also involve access, connections to existing systems, exterior restoration, drainage or other site work. Ask the contractor to distinguish identified work from items still awaiting design or investigation. Discuss how construction access will affect the existing household and where materials might be delivered and stored. End the feasibility conversation with a short list of next steps, a responsible person for each and the information needed before a detailed construction proposal can be prepared.
Your planning checklist
- Define the intended use and must-have spaces.
- Gather available plans and records without assuming they are current.
- Ask the responsible design team to confirm property-specific requirements.
- Include connections, site access and restoration in the scope discussion.