When planning your Accessory Dwelling Unit (ADU), one of the most important — and often overlooked — steps is understanding your property lines and how close you can legally build to them. If you’re not sure where your lot begins and ends, or how much space you have to work with, it may be time to bring in a pro: a licensed land surveyor.
Why Property Lines Matter for ADUs
Most cities and towns have zoning rules that require your ADU to be set back a certain distance from your side, rear, and front property lines. These are called setbacks, and they can make or break the location (or even the size) of your ADU.
If you’re guessing where your property line is — or relying on a fence or hedge that was already there when you bought the house — you may be setting yourself up for problems during permit review. Municipalities often require precise documentation of where your ADU will sit on the lot, especially if you’re building near the minimum setback line.
When You Might Need to Hire a Surveyor
You should consider hiring a surveyor if:
✅ Your property lines are unclear or disputed
✅ You want to build close to the edge of your lot
✅ Your lot has irregular boundaries or odd angles
✅ You need a formal plot plan for your permit submission
✅ You’re combining your ADU permit with a zoning variance request
Even if you’re confident in your lot boundaries, many towns require a plot plan drawn by a licensed land surveyor as part of the building permit application — particularly if your ADU is detached.
What Does a Surveyor Do?
A licensed land surveyor can:
- Locate your official property boundaries
- Map existing structures, driveways, and easements
- Identify encroachments or zoning conflicts
- Prepare a certified plot plan showing your proposed ADU and how it complies with setback and zoning requirements
This plan becomes a key part of your permit submission and can help prevent delays, revisions, or rejections.
How Much Does a Survey Cost?
Costs vary based on property size, complexity, and location, but in most cases, you can expect to pay:
- $800–$2,000+ for a standard boundary survey and certified plot plan
- Additional fees if your lot is heavily wooded, sloped, unusually shaped, or not well-documented
While this is a notable investment, it can save you thousands in redesigns or legal issues later on.
Can Dwelly Help?
Absolutely. If you’re working with a Dwelly design and are unsure about your site conditions, we can help you figure out if a surveyor is needed, and connect you with trusted professionals in your area who have experience supporting ADU projects.
The bottom line?
A land survey might not be the most exciting part of building your ADU — but it’s one of the smartest. Getting your boundaries and setbacks right from the start helps ensure your project stays on track, on budget, and fully code-compliant.
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