How do I know if I’m allowed to build an ADU on my property? How big can it be?

ADU requirements vary by city and jurisdiction. Your property’s zoning, lot size, setbacks, and other local regulations can determine whether an ADU is allowed and what size it can be. Maximum ADU size requirements also vary by location. We can help you understand the regulations that apply to your property and determine what may be possible before moving forward with design and permitting.

How many rounds of revisions are included in the conceptual phase until I am satisfied with the design?

The number of revisions included during the conceptual design phase depends on the scope of your ADU project and the design package. We work closely with you to refine the design and make sure the layout, features, and overall concept align with your goals and property. Any revision limits or additional design services will be discussed with you upfront before moving forward.

ADU Feasibility Study in Tampa Bay

Most homeowners who call us have already done two or three hours of online research on ADUs before the first conversation. They know what an ADU is. They think they know what it costs. What they almost never know is whether their specific lot is eligible, what size unit the zoning code actually allows on their parcel, and which three or four constraints will shape the design from day one.

A feasibility study answers those questions before anyone is asked to sign a construction contract. This page explains what a feasibility study is, what it checks, when you need a paid one, and when a free lot eligibility call is enough.

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What a Feasibility Study Actually Checks

1. Zoning and overlay status: Base zoning district, whether ADUs are permitted by right or conditionally, overlay districts, Extended Family Residence rules (City of Tampa), pending code amendments. 2. Lot size, setbacks, and siting: Minimum lot size for your zone, front/side/rear setbacks, separation between primary and accessory structures, maximum allowable ADU square footage, height limits, architectural match requirements. 3. Infrastructure and utilities: Existing electrical service capacity (100-amp vs. 200-amp), sewer lateral age and condition, water service line size, natural gas availability, septic system capacity. 4. Flood, storm, and soil: FEMA flood zone designation, base flood elevation vs. existing grade, Coastal Storm Area designation, wind exposure category and ultimate design wind speed, soil bearing capacity. 5. Site constraints: Tree preservation ordinance impacts, easements, impervious coverage maximum and current coverage, stormwater retention requirements. 6. Market and intent: For family use — accessibility needs and §193.703 tax benefit eligibility. For rental — comparable rental rates, jurisdiction-specific rental rules, HOA covenants.

Four Ways a Tampa Bay Lot Can Disqualify Your ADU

A granny flat in Tampa Bay is almost always one of three forms: 1. Detached backyard granny flat: Its own small building in the back or side yard. Most privacy, highest cost, tends to appraise best. Typical size 500–950 sq ft. 2. Garage conversion granny flat: Your existing attached or detached garage reframed as a living unit. Lower cost, faster permit, but requires code-compliant egress, kitchen, bathroom, and HVAC. 3. Attached granny flat (addition): New square footage added to the main home with its own entrance, kitchen, and bathroom. Shares a wall with the primary. Often the best answer when the lot is tight. Every one of these has to meet Florida Building Code, 2023 Edition (8th). That means hurricane-rated openings, wind-uplift connectors, and a roof system rated for the wind zone your address sits in. In most of Pinellas County, that is Exposure C or D and a 140–150 mph ultimate design wind speed.

When to Stop at the Free Call vs. Pay for a Deeper Study

Free call is sufficient when: You are at least 6 months from building. You just want to confirm the lot is eligible and the rough cost is in range. You are still deciding between ADU types or deciding whether to move forward at all.

Paid feasibility study is worth it when: You are within 2–3 months of wanting to start design. You are buying a property specifically for its ADU potential. The lot has complicating factors (flood zone, septic, historic overlay, very small or irregular). You are comparing two or three lots. You are planning a rental-intent ADU and need a defensible rental rate projection before committing capital.

Frequently asked questions

Garage Conversion

Detached ADU

ADU Permitting

Granny Flat

Mother-in-law suite

ADU Feasibility Study

ADU size requirements vary by city and jurisdiction. The minimum or maximum size may depend on factors such as your property’s zoning, lot size, setbacks, and local regulations. Beyond what is allowed, the ideal ADU size depends on how you plan to use the space and the needs of your household. We can help you understand the applicable requirements and determine a practical size for your ADU before moving forward with design and permitting.