ADU and Topo/Boundary Survey

[Hari Narayanan]

Hello fellow BP users,

I am about to start construction of ADU in the backyard of my property in East Bay. I was wondering if I need to get a Top or a Boundary survey done? Can someone who has built ADU in their backyard weigh in please? What do the inspectors ask for to ensure the new detached ADU is not encroaching in to the 4' setback from the property line?

I checked with the City and both the Planning and the Building departments said they don't require a Survey. But I should get one if I want to be doubly sure about the setbacks.

What do you all think?

Also, does anyone has a recommendation for a reliable Surveyor they have worked with in the past, could they please DM me?

Thank you!

[Whitney Hill]

@Thomas Blocker Wanted to chime in with perspective here, as we have designed, permitted, and built ~100 ADUs in San Diego County. Please get a topographic survey. This is so important to avoiding massive issues when you ultimately begin sitework. A planimetric & limited topographic survey will add $2500-$3000 to your project -- it's a cost we actually front for our clients (but they are on the hook for if they end up not building the project). Before we made this step mandatory in our projects, we had to either absorb or pass along up to $20K+ in changes to sitework & foundation costs. Related to this, please also make sure and get a utility planning study done as part of your feasibility process. This means not only mapping the location of your existing utilities, but engaging with an experienced provider who knows how to work with your local utilities. Most new construction ADU projects will need a panel upgrade, potentially a conduit upgrade and right of way work depending on your utility setup. This is extremely complex work if you don't know what you're doing, can also delay your project by 6-9 months if you don't plan accordingly. Google "utility planning consulting."

More about surveys:
A planimetric survey maps out the existing conditions of your property, including the layout of buildings, trees, driveways, and other significant features. It provides a detailed “bird’s-eye view” of the property, which is crucial for understanding how the land’s contours and features will interact with the proposed ADU, which can significantly affect both the cost and feasibility of the project.

A limited topographic survey goes a step further by providing the vertical elevations of the property. This type of survey is crucial for ADU projects because it reveals the lot’s contours, slopes, and elevation changes, which are vital for foundation design and drainage planning. The “limited” aspect refers to focusing on areas critical for the project at hand, rather than a full topographic survey of the entire property, which might be necessary for larger-scale developments. For an ADU project, this means concentrating on the proposed construction area and its immediate surroundings to ensure that the ADU integrates seamlessly with the existing terrain.

Including a planimetric & limited topographic survey in the feasibility study allows for a more accurate assessment of construction costs and potential site-related challenges. It’s a proactive step that helps avoid costly surprises during construction and ensures that the ADU is designed with a full understanding of the site’s topographical nuances.

A Building Verification Survey (BVS) verifies that the ADU is accurately placed on-site in relation to the property lines and in accordance with the approved plans. The BVS is a follow-up field survey conducted at the installation of the foundation to verify the ADU’s location. In order to complete a BVS, note that a Boundary Survey must first be conducted to locate the property lines.

A BVS is a specific requirement that some cities place on projects that propose a new structure. Some cities require building verification surveys in all cases, while others require them when the ADU is within 1′ of a setback.