Frequently Asked Questions About ADUs
Get answers to the most common questions about Accessory Dwelling Units on Cape Cod, from regulations and permits to costs and construction timelines.
Your ADU Questions Answered
Planning and building an Accessory Dwelling Unit involves many considerations, from local regulations to design choices, construction requirements, and financing options. We've compiled answers to the most frequently asked questions to help guide your ADU journey on Cape Cod.
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Building an ADU on Cape Cod typically requires several permits, though specifics vary by town:
- Building Permit: Required for any new construction or major renovation.
- Septic/Wastewater Approval: You may need a Board of Health permit for septic system modifications.
- Electrical Permit: Required for all electrical work.
- Plumbing Permit: Required for all plumbing installations.
- Conservation Commission Approval: May be required if your property is near wetlands or in environmentally sensitive areas.
- Special Permits: Some towns require a special permit or site plan review for ADUs, particularly for detached units.
We recommend starting with a meeting at your town's Building Department to understand the specific requirements for your property. As part of our ADU services, we can guide you through the entire permitting process.
Yes, most Cape Cod towns now allow some form of Accessory Dwelling Units, but regulations vary significantly between communities. As of 2024:
- Eastham, Wellfleet, Provincetown, Orleans, and Barnstable have progressive ADU bylaws that encourage their development.
- Truro, Chatham, Brewster, and Harwich allow ADUs with moderate restrictions.
- Dennis, Yarmouth, and Falmouth permit ADUs but may have more limitations on size, design, or usage.
Each town updates their bylaws periodically, often becoming more ADU-friendly over time. We stay current with all local regulations and can provide the most up-to-date information for your specific town.
ADU costs on Cape Cod vary widely based on type, size, finishes, and site conditions. Based on our recent projects, here are typical cost ranges (as of 2024):
- Conversion ADUs (existing spaces like garages, basements):
$250-$400 per square foot ($80,000-$150,000 total) - Attached ADUs (additions to existing homes):
$350-$450 per square foot ($140,000-$225,000 total) - Detached ADUs (standalone structures):
$400-$550 per square foot ($160,000-$300,000 total)
These estimates include design, permitting, site work, construction, and standard finishes. Factors that can significantly impact costs include septic system upgrades, complex site conditions, high-end finishes, and utility connections.
The best ADU type depends on your specific property characteristics, budget, and goals. Here are the main options:
- Detached ADUs: Best for larger lots, maximum privacy, minimal disruption to main home
- Garage Conversions: Best for properties with existing garages, limited budgets, faster timelines
- Basement Conversions: Best for homes with walkout basements, budget-conscious projects
- Attached Additions: Best for limited lot space, easier utility connections
We offer a comprehensive site assessment service to evaluate your property and help determine which ADU type would be optimal.
Short-term rental regulations for ADUs vary significantly by town on Cape Cod. Some towns prohibit short-term rentals in ADUs entirely, while others allow seasonal rentals with specific registration requirements.
If short-term rental usage is important to your plans, we recommend checking your town's specific ADU bylaw for rental restrictions and reviewing your town's short-term rental regulations separately.
ADUs contribute significantly to addressing Cape Cod's housing challenges by providing workforce housing, creating "invisible density" that preserves community character, and offering smaller, more affordable units that diversify the housing stock.
Cape Cod has lost approximately 3,000 year-round housing units to seasonal use since 2010. Each new ADU created for year-round occupancy helps counteract this trend.
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