Site Assessment in San Francisco, CA
A site assessment for an ADU in San Francisco is a structured investigation of your lot, your existing structures, and the city’s specific building rules, completed before any design work begins. Most San Francisco site assessments run $500 – $2,500 depending on lot complexity, slope, soil conditions, and how deep into city records we need to go. At Sutton ADU San Francisco, we handle this in-house as part of our ADU Design & Permitting process, so you get one written report that tells you exactly what can be built, what it will likely cost, and what obstacles exist before you spend a dollar on architecture. Call (831) 272-7212 and we’ll schedule an assessment, typically within 7 – 10 days.
This is the step that separates a smooth build from a six-month stall at the planning counter. We walk the property, pull the pertinent city records, check the soil and slope, and map the setback constraints (the required gap between your new structure and the property line). Then we hand you a written site assessment report with the real numbers, not a verbal shrug. The Threshold Standard applies here just like it does on every Sutton project: a written price before work begins, a name and photo of who’s coming to your door before the visit, and our 365-Day Done Right Promise covering everything we do for a full calendar year.
Homeowners who choose Sutton for site assessment are often the same people who will later choose us for the full build. They’re parents who want a Tuff Shed conversion for an in-law, or homeowners weighing a Boxabl unit against a stick-built addition, or older San Franciscans who simply want to know who is walking their property line. We built our process for those exact people.
When You Need Site Assessment
If you’re wondering whether a site assessment is worth the time and money, it almost always is. Here are the specific situations where it’s essential:
- You’re considering a detached ADU in a neighborhood with strict planning review. The Richmond, Sunset, and Noe Valley all have distinct lot patterns and planning overlays. A site assessment catches the restrictions before you pay a designer to draw something the city will reject.
- Your lot isn’t flat. A significant portion of San Francisco residential lots sit on slopes of 10% or more. Slope triggers different foundation requirements, drainage rules, and in some cases, geotechnical review. We measure it during the assessment so your budget reflects reality.
- You have an existing garage or side yard you’d like to convert. We check setbacks, ceiling heights, foundation condition, and whether the existing structure can legally be converted or should be replaced. Tuff Shed and similar prefab structures often need different treatment than a site-built garage.
- You’ve heard conflicting opinions from contractors or neighbors. One person says “no problem,” another says “that’ll never get approved.” A site assessment gives you the documented facts: zoning, height limits, setback requirements, and any historical or environmental overlays on your specific parcel.
- You want a realistic budget before you commit to design and permitting. The most common financial mistake in ADU construction is designing first and discovering site constraints second. An assessment front-loads those discoveries, so your budget has the real numbers in it from day one.
- You’re comparing prefab versus traditional construction. Some lots suit a Plant Prefab or Boxabl unit beautifully. Others don’t, due to crane access, street width, or utility placement. Our assessment tests your lot against the actual requirements of the product lines you’re considering, so you don’t fall in love with an option that won’t physically work on your property.
Our Site Assessment Process
Here’s how a site assessment unfolds with Sutton ADU San Francisco. The process is designed to be transparent at every step, and you’ll get the written report regardless of whether you proceed with us for the full build.
- You call and speak to a person. No voicemail trees, no online form that disappears into a queue. You reach a live person at (831) 272-7212, who asks a few questions about your property and what you’re hoping to build. We schedule the assessment visit.
- We send the name and photo of the technician before the visit. This is the Threshold Verified standard, and it’s non-negotiable. You’ll know exactly who is arriving, what they look like, and when to expect them. When they arrive, they’ll be in a clean, marked uniform and show a photo ID badge at the door.
- We walk the property with you. The assessor measures the existing footprint, tests the slope, checks the condition of any structures you’re considering converting, and reviews access points. We want you on the walk if you’re available, because you’ll point out things we might not notice: the way water pools near the back fence, the neighbor’s tree that overhangs the property line, the past drainage issue the previous owner mentioned.
- We pull the city records. Zoning, overlay districts, any open permits or code violations tied to the address, historical resource status if applicable, and utility easements. San Francisco planning records can be dense; we know what to look for and how to read it.
- We prepare the written site assessment report. The report includes the measured lot dimensions, slope analysis, zoning summary, setback requirements, height limits, any environmental constraints (erosion zones, creek setbacks, tree preservation rules), and a realistic preliminary cost range for the ADU type that fits your lot. You get this in writing, by email and in hand. No verbal summaries.
- We review the report with you and answer every question. You’ll sit with the assessor, either on-site or by phone, and go through the report line by line. If a constraint is a dealbreaker, we tell you. If there’s a workaround, we tell you that too, and what it will add to the budget. If you’re weighing options like a James Hardie-clad addition versus a modular unit, we’ll discuss how the site findings affect each choice.
Site Assessment Pricing in San Francisco
Site assessment in San Francisco typically runs $500 – $2,500. The range is wide because every lot in this city is different, and the scope of the assessment shifts with the property.
| Assessment Component | Typical Cost in San Francisco |
|---|---|
| Standard lot walk and written report | $500 – $900 |
| Sloped lot or hillside property | Add $300 – $600 |
| Existing-structure condition review (for conversions) | Add $200 – $500 |
| Deep-dive city record pull with historical/overlay research | Add $150 – $400 |
| Geotechnical soil testing (if required) | $1,200 – $2,500+ |
Several factors move the price. A flat lot in the Sunset with a standard 25-foot-wide parcel and no unusual features sits at the lower end. A hillside lot in Diamond Heights or a property in a historical overlay district trends toward the higher end. Slopes over 10% often trigger geotechnical review, which is a separate line item and varies by firm. A garage conversion candidate where the foundation and framing need close inspection also adds a modest amount.
What you will not get from Sutton is a variable price that grows after we start. The written price comes before the assessment begins, and it stays the written price. If we uncover something during the research that requires additional work, we’ll stop and tell you what the add-on would cost before doing it. No silent scope creep on the bill.
Here’s the part most San Francisco homeowners appreciate: if you move forward with Sutton for the full ADU design and build, we credit the site assessment fee toward your project. So the assessment effectively costs you nothing on a full build. Call (831) 272-7212 for a free phone estimate of your assessment range before we schedule the visit.
Key Takeaways
- A site assessment is the front-end due diligence that prevents budget-busting surprises later in ADU Design & Permitting.
- Most San Francisco site assessments run $500 – $2,500, with the fee credited toward your full build if you proceed with Sutton.
- We send the name and photo of your assessor before the visit. Every time. That’s the Threshold Standard.
- The written report is yours regardless of whether you hire us for the full project.
- We know the San Francisco planning landscape: setbacks, height limits, slope rules, and overlay districts across every neighborhood from Noe Valley to the Outer Sunset.
- Our 365-Day Done Right Promise covers the assessment work for a full year. If we got something wrong, we’ll come back and fix it at no cost.
What a Site Assessment Catches That a Walkthrough Misses
A contractor who walks your yard for 20 minutes and says “yeah, you can build here” is not doing a site assessment. That’s a drive-by opinion. Here’s what a proper assessment uncovers:
Setbacks and property-line constraints
San Francisco’s density means your lot is probably tighter than the average suburban parcel. The side-yard setback requirement (the minimum gap between your structure and the property line) and rear-yard rules vary by zoning district. An assessment measures your exact footprint against the code, for your specific zone, not a city-wide average. In neighborhoods like the Inner Richmond, where lots are commonly 25 feet wide, those few feet of setback can mean the difference between a 700-square-foot ADU and one that has to shrink to 500.
Slope and foundation implications
San Francisco is famous for hills, and a surprising number of residential lots have gentle slopes that the homeowner never really thinks about until they try to build. A 5% slope is manageable with standard foundations. A 15% slope changes the structural design, drainage plan, and cost. We measure the actual grade during the assessment, and we’ll tell you plainly if your lot needs a geotechnical report before design can proceed.
Utility placement and easements
Where your water, sewer, and gas lines run affects where the ADU can sit. Some San Francisco lots have easements running through the exact spot where the homeowner envisioned a new unit. The assessment identifies these before the architect draws a line. Moving a sewer lateral is expensive; never designing over it is cheap.
Existing structure viability
If you’re converting a garage or outbuilding, we check whether the existing slab is adequate, whether the walls are plumb and sound, and whether the roof structure can be preserved. Some garages in San Francisco are beautiful candidates for conversion. Others have foundation issues that make replacement cheaper than retrofit. The assessment tells you which one you have. If you’re considering a Tuff Shed structure as the base, we’ll test that specific scenario against code.
Product-line fit
We work with recognized ADU product lines including Boxabl, Plant Prefab, and others. But each has real siting requirements: crane access, delivery vehicle clearance, foundation specifications. Our assessment checks your street width, overhead obstructions, and site access against the actual requirements of the products you’re considering. A prefab unit is often a smart financial choice; receiving it on a street that can’t accommodate the delivery truck is not something you want to discover on delivery day.
Why Site Assessment Comes Before Design, Not After
The traditional sequence in residential construction is design first, then figure out the site. That sequence is expensive. Here’s why we reverse it:
A set of architectural drawings for a detached ADU in San Francisco typically costs $8,000 – $15,000 or more, drawn before any site constraints are formally documented. If the drawings then hit a setback violation or a slope issue the designer didn’t know about, you’re paying for revisions or starting over. The site assessment costs $500 – $2,500 and gives the designer the documented reality before they draw the first line. That’s the order that protects your money.
We also recommend the assessment before you commit to a prefab brand. Homeowners sometimes contact us already emotionally committed to a Boxabl or Plant Prefab unit because they saw one online or a friend installed one in a different city. We’re glad to work with those product lines, but the right order is: assess the site first, then choose the product that fits the site. Doing it backwards leads to disappointment and wasted deposits.
The same logic applies to exterior choices like James Hardie cladding systems. Those decisions matter, but they’re design-phase choices. The site assessment comes first and tells you the envelope you’re working within.
San Francisco Specifics: Rules That Shape Your Assessment
Every city has quirks, and San Francisco’s are well documented. Here are the ones that most frequently show up in our site assessments:
- Zoning districts with overlays. Some neighborhoods, especially those with older housing stock like Noe Valley, Bernal Heights, and portions of the Mission, sit within historical resource overlays or special use districts. These add review time and sometimes design restrictions. Our assessment flags any overlay on your parcel before you invest in design.
- Height limits and floor-area ratio. San Francisco limits how much of your lot can be covered by structures. For a rear-yard ADU, the buildable envelope is often smaller than homeowners expect. We calculate the exact buildable area for your parcel during the assessment.
- Slope and seismic considerations. The city has strict foundation and structural requirements, and slope stability can trigger additional engineering review. We won’t design or build on a slope without proper geotechnical input, and the assessment tells you whether that input is required for your lot.
- Street and access constraints. Some San Francisco streets are narrow, some are one-way, and some have overhead power lines at awkward heights. For prefab deliveries, crane placement, and even concrete trucks, access matters. We verify it during the walk, not after the purchase order is signed.
FAQs – Site Assessment
How much does a site assessment cost in San Francisco?
A site assessment in San Francisco typically costs $500 – $2,500, with flat lots at the lower end and sloped or overlay-restricted lots at the higher end. The fee is credited toward your full ADU project if you proceed with Sutton. Call (831) 272-7212 for a free phone estimate of your specific range.
How long does a site assessment take?
The on-site walk typically takes 1 – 2 hours, and the full assessment including city record review and report preparation is usually completed within 5 – 10 business days. We’ll give you a specific timeline when we schedule the visit.
Do I get a written report even if I don’t continue with the build?
Yes. The site assessment report is yours, in writing, regardless of whether you hire Sutton for the full design and build. We don’t hold the findings hostage.
Can you assess a site for a prefab ADU like a Boxabl or Plant Prefab unit?
Yes. We assess cr
