How to research your San Diego property before building an ADU

Before you spend a dollar on ADU design, pull the records that decide what your lot will allow: your building permit history, your SDG&E service details, your title report, your parcel map, the soils layers for your parcel, and your sewer lateral record, then check your fire hazard zone. Every one comes from an official source, and our free Property Records Toolkit points you to each with exactly what to ask for. Here is the walkthrough, in the toolkit's order, and why each record changes what we build.

Why we research the lot before we draw the ADU

Two identical ADUs on different lots can be $80,000 apart, and the difference is the lot, not the building.

Our ADU Project Planner asks the same property questions we ask on a site visit: your lot's slope, how equipment will get to the ADU spot, how close the unit sits to the nearest property line, your electrical panel and its size, sewer or septic and where the lateral is, your water meter size, gas, and whether the utility run to the ADU spot is a long one. Answer yes and the planner adds the allowance range from our ADU cost guide; answer not sure and it flags the item instead of charging you. The other property-specific costs (soils, a survey, fire zone, sprinklers, demolition, driveway, drainage) are listed as price factors and confirmed in your property review. These records turn a not sure into a checkmark.

Record	Source	Settles
Building records and permits	San Diego County Assessor / Recorder	Unpermitted work
Service upgrade details	SDG&E Builder Services	Electrical panel upgrade
Title report	Your title company	Easements, where the unit can sit
Parcel map	ParcelQuest (County Assessor data)	Lot lines, setbacks, survey
Soils and environmental layers	SanGIS regional mapping	Poor soils, grading, drainage
Sewer lateral record	Your sewer provider	Trench or pump, utility run, street work
Fire Hazard Severity Zone	CAL FIRE	WUI requirements, fire sprinklers

Step 1: Request your building records

The first card is the building records request from the San Diego County Assessor / Recorder. Complete the county's authorization form and email it in to request the prior building records and permits on file.

This is where unpermitted work shows up. If the paperwork says two-car garage and what is standing is a garage with a bathroom, somebody skipped a permit, and we would rather know that now than hear it from the plan checker. On a garage conversion, old permits also tell us what the slab and framing were approved to be.

Cities keep their own permit files too; Oceanside uses its eTRAKiT permit portal. We point you to your city's records pages during your property review.

Step 2: Find out what an SDG&E service upgrade involves

Card two is SDG&E service upgrade details from SDG&E Builder Services. Create an account and fill out the application to learn what an electrical or gas service upgrade entails. Per the toolkit, the site meeting with an SDG&E planner takes about 5 to 6 weeks total, so start early.

An ADU adds a kitchen, a water heater, and heating and cooling to your electrical load, and many older homes run 100-amp panels that can't carry a second dwelling. The planner asks whether your panel is 100A, 125A, or 200A; a photo of your main breaker and meter usually answers it. If an upgrade is needed, the allowance runs $5,500 to $25,000, and SDG&E's answer tells us what a service upgrade would actually involve on your property. Water is separate: the planner asks for your meter size, and your water provider should have it on file.

Step 3: Map where the unit can sit

Title report: recorded easements

This card has no link: get hold of the title report from when you purchased the property; your agent, broker, or title company can help. An easement is someone else's right to use part of your land, for utilities, access, or drainage, and you generally cannot put a dwelling on top of one.

Parcel map: lot lines and setbacks

Download your parcel map from ParcelQuest, which runs on County Assessor data: search by your property's APN number, open the property detail, and click Download Assessor Map. Your APN is on your property tax bill.

Every setback is measured from those lines. State law requires cities to allow an ADU with 4-foot side and rear setbacks; the City of San Diego allows zero for single-story units at or under 16 feet in most of the city, Vista wants 5 feet of eave-to-eave separation between a detached ADU and the house, and San Marcos wants 10 feet. Our city guides cover each one. The line that bites most often is the 5-foot rule: within 5 feet of a property line, code requires additional fire-rated construction.

An assessor map is not a survey. If your fence, the map, and your neighbor's memory disagree, a survey becomes a real line item ($2,500 to $7,500 in our planner), and a licensed surveyor sets stakes before anything gets poured, as on our Pacifica model in Oceanside.

Our Pacifica model in Oceanside, where licensed surveyors set stakes before construction. A parcel map alone cannot do that.

Soils and environmental layers

SanGIS regional mapping shows general soil and environmental constraints for any County parcel. Three planner allowances live in the dirt: poor soils can mean a special foundation ($10,000 to $50,000), slope means grading and retaining walls ($15,000 to $100,000 on sloped lots, the biggest wildcard we price), and ponding near the ADU spot means new drains. SanGIS is not a soils report, but it tells us early whether to expect one.

Step 4: Run the Sewer Lateral Lookup

Next is the Sewer Lateral Lookup. Type your address and click Find My Provider. For a Vista address the toolkit names the likely provider: Vista / Buena Sanitation District, 760-726-1340 ext. 1372. Elsewhere it points you to your city's public works department or local sanitation district. You also get the exact request to send, with a Copy Request button: "I'm considering an ADU at [your address]. Can you provide any available sewer lateral map, sewer permit, as-built, or record showing where the existing private sewer lateral connects to the public sewer main?"

A Nucave crew opening a utility trench. Where the lateral sits, and how deep, decides how much of this you pay for.

This is the record we care about most, because the lateral's location and depth decide whether the ADU drains by gravity or needs a pump. A lateral out the front of the house with the ADU in the back corner means a long utility run, roughly 100 feet or more from the house connections, with an allowance of $15,000 to $40,000. A new tap on the main in the street means work in the public right of way, $30,000 to $60,000. We are licensed to do that work ourselves; our sewer connections guide explains it. On septic, ask your septic company whether the system will support the new unit.

Step 5: Run the Fire Zone Lookup

Enter your address and click Check My Fire Zone. The toolkit copies your address and opens CAL FIRE's Fire Hazard Severity Zone viewer in a new tab; click the map's search (the magnifying glass), paste your address, and screenshot the result.

In a hazard zone, often called a WUI or wildland-urban interface zone, an ADU carries extra fire-rated requirements. The planner carries $5,000 to $25,000 for enhanced fire-rated construction near property lines or in fire hazard zones, and a separate fire sprinkler allowance; ADUs generally need sprinklers only when the main house has them. The zone can move your placement too: in the City of San Diego, High and Very High zones pull setbacks back to a 4-foot minimum even where the citywide rule is zero. We verify your status in your property review.

When a record is missing

Records go missing: laterals were never mapped, permits were never scanned, the title report is in a box somewhere. Here is what we do.

• Call the city. Ask the building department for the permit history and public works for the lateral record, with your address and APN in front of you.
• Order the record. Request the county building records and your title report the week you start the planner.
• Keep it in writing. Email your requests, keep the replies, and use the toolkit's request text so you ask for the right thing the first time. Even a written "no record on file" is useful: it tells us to go look in the field.
• Go find it in the field. With no sewer record, a camera run from your cleanout traces the route and depth of the lateral.
• Do not guess. The planner never charges you for a not sure; it flags it, and the property review resolves it.

What to have ready before a consultation

Our first phase is the On-Site Consultation: we walk the property with you and take photos and measurements. Nothing here is required to book, but every item sharpens the estimate:

• Address, APN, and the parcel map download
• Easement pages from your title report
• Permit history and any old plans
• A photo of your main electrical panel and meter, plus water meter size and whether the house has gas
• Sewer or septic, where your cleanout is, and any lateral record
• A screenshot of your fire zone result
• Where the ADU goes, how close to the nearest property line, and how far from the house connections
• Slope, access (can a mini excavator reach the spot), and whether you are in an HOA

Frequently asked questions

How do I find the sewer line on my property? Ask your sewer provider; the toolkit's Sewer Lateral Lookup names the likely provider and gives you the exact request. If nothing is on file, a camera run from your cleanout traces the line.

How do I look up a parcel map in San Diego County? On ParcelQuest, which runs on County Assessor data: search by your APN, open the property detail, and click Download Assessor Map.

How do I check if my property is in a fire hazard severity zone? Use the toolkit's Fire Zone Lookup. It opens CAL FIRE's official viewer with your address copied; paste it into the map's search.

Do I need a survey to build an ADU? Not always. When the map, the fences, and the neighbors agree, we can often work from the map; when they disagree, or the unit sits close to a line, a survey is money well spent.

Will my 100-amp panel handle an ADU? Often not on its own. Photograph your main breaker and meter, answer the planner's panel question, and start the SDG&E application early.

Bring us what you found

Pull what you can, screenshot what you find, and book a free consultation. We will walk the lot, read the records with you, and tell you what the property will and will not allow before you spend anything on design. Prefer to talk first? Call (760) 310-2393.