Building an ADU: What Every Homeowner Should Know Before Getting Started
- Elijah Ajayi
- Feb 3
- 3 min read
Accessory Dwelling Units (ADUs) are one of the smartest ways to add living space, generate rental income, or create housing for family — but they also come with unique planning challenges.
Before jumping into floor plans or finishes, here are the core basics every homeowner should understand when building an ADU.
Why Build an ADU?
Start by defining your goal:
Rental income
Multigenerational living
Guest house or home office
Increasing property value
Your purpose affects everything — size, layout, budget, and long-term return on investment.
Pro tip: Knowing why you’re building helps designers, engineers, and contractors guide you more efficiently.
Septic vs. Sewer: A Critical First Step
One of the very first things to confirm is how your property handles wastewater.
If You’re on Sewer
Typically easier and less expensive to connect an ADU.
Some municipalities require capacity upgrades when adding bedrooms.
Connection or tap fees may apply.
If You’re on Septic
This is where many projects slow down.
You may need:
A soil percolation test
Septic system evaluation
Possible system expansion or replacement
If your existing septic system can’t support the added dwelling, costs can rise quickly.
👉 Always verify septic vs sewer before paying for design plans.
Property Line Setbacks & Zoning Rules
Every city and county has zoning regulations that control where and how an ADU can be built.
Key items to research:
Front, side, and rear setbacks
Maximum ADU size
Height limits
Lot coverage
Parking requirements
Detached vs attached ADU allowances
These rules determine:
Where your ADU can sit
How large it can be
Whether your project is feasible at all
A quick zoning check early can save months of redesign later.
Utilities & Site Conditions Matter More Than Most People Expect
Beyond wastewater, homeowners should also consider:
Electrical service capacity
Water line sizing
Gas availability
Drainage and grading
Tree protection requirements
Easements on the property
A flat backyard with nearby utilities is far more affordable than a sloped lot with long trench runs.
ADU Cost Ranges: What Should Homeowners Budget?
While every project is different, here are realistic rough ranges for fully permitted, professionally built ADUs:
Nationwide Average
$150,000 – $350,000+
Costs vary based on size, finishes, utilities, site work, and local regulations.
Georgia (Typical Range)
$130,000 – $280,000
Georgia tends to be more affordable than West Coast markets, but septic upgrades, grading, or utility extensions can still add significant cost.
Atlanta Metro Area
$160,000 – $325,000+
In Atlanta, pricing is often higher due to:
Urban zoning requirements
Permit timelines
Utility connection fees
Limited site access
Parking requirements
Most homeowners should also plan for a 10–15% contingency for underground or permitting surprises.
Where Should Homeowners Start?
Here’s a proven starting path:
Step 1 – Confirm Utilities
Determine septic vs sewer.
Step 2 – Check Zoning
Review local ADU rules, setbacks, and size limits.
Step 3 – Preliminary Site Review
Look at access, grading, utilities, and buildable area.
Step 4 – Establish a Budget Range
Include permits, utilities, construction, and contingency.
Step 5 – Move Into Design
Only after feasibility is confirmed.
Want Us to Handle the Research for You?
Navigating zoning, setbacks, utilities, and feasibility can feel overwhelming — especially if you’re doing this for the first time.
If you’d rather skip the guesswork, we offer professional ADU feasibility research, including:
✔ Zoning and setback analysis✔ Septic or sewer verification✔ Utility capacity review✔ Site constraints evaluation✔ Preliminary budget guidance
We’ll tell you what’s possible on your lot — before you spend money on plans that may not work.
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