The lot looks fine. That's not the same as verified.
A flat parcel with a for-sale sign tells you nothing about what's under it, what's crossing it, or what the city will let you build on it. Every item below has killed a deal somewhere in the San Gabriel Valley — usually quietly, in escrow, long after the excitement of finding the lot wore off.
This isn't a post-contract list. Most of it belongs in the offer stage, before you're spending real money to learn the answer is no.
The checklist
| Item | What to verify | Deal-killer threshold |
|---|---|---|
| Topography | Flat vs. sloped — eyeball it, then confirm with a survey | Meaningful slope adds retaining walls, deep piers, or caissons; caissons alone run $3,000–$5,000+ each — see building on a hillside lot |
| Fire access | That a fire apparatus road can reach within 150 ft of the house at a grade no steeper than 15% (LA County Fire Code §503.1.1, §503.2.7) | No legal route to the building pad — this ends a hillside deal outright, and no design fixes it |
| Soil quality | Evidence of fill, prior contamination, or wetlands | Fill means excavation and haul-out; a wetlands designation can take a parcel off the table entirely |
| Utility access | Water, sewer, and gas already in the street; existing laterals to the parcel — and for water, capacity at your pad elevation, not just presence in the street | No mains in the street means a costly county extension, billed to you. On a hillside, insufficient water pressure at elevation can mean a required water tank, or no build at all |
| Zoning — by right | Can you actually build what you think you can build, under current setback, height, and parking rules | A zoning confirmation letter from the city or county disagrees with your density study |
| Zoning — rezone/upzone | If the project requires a zone change, the process, timeline, and neighbor-engagement path | Adds months to years to your timeline — treat it as a separate, longer due-diligence window, not a formality |
| Title | Clean title, recorded easements, and unrecorded utilities crossing the parcel | Any easement or deed restriction sitting on the buildable footprint |
| Survey | A residential survey at minimum; ALTA and topo surveys for commercial or sloped sites | Actual lot dimensions or easement locations differ from what the seller represented |
| Geotech | Soil borings to confirm bearing capacity and check for groundwater | Unsuitable fill or high groundwater requiring deep foundations |
| Environmental — Phase I | A records search for prior contamination (old tanks, industrial or commercial history) | Any "Recognized Environmental Condition" found — triggers a Phase II |
| Environmental — Phase II | Physical soil, groundwater, or vapor testing, only if Phase I flags a concern | Confirmed contamination requiring remediation before the site can be developed |
| Stormwater retention | Whether the parcel's size or disturbance area triggers a retention requirement | Larger commercial or multi-unit sites in cities with stricter runoff rules — confirm with a civil engineer before you assume a small lot is exempt |
| Wildfire/constraint flags | Whether the parcel sits in a Very High Fire Hazard Severity Zone or other overlay | A VHFHSZ or historic-overlay flag can add material, clearance, and sprinkler requirements and adds review — check your city's page (via SGV regions) for its constraint flags |
In the SGV specifically: utility and easement records live with LA County Public Works and the Assessor's parcel maps, not a generic "county office." Title and easements run through a title company or the LA County Registrar-Recorder — if you're already in escrow, ask your title rep for an easement map; they'll pull every recorded easement on the parcel and mark it for you directly, no separate research required. Check DTSC's EnviroStor database yourself before you pay a consultant to search it for you.
Most of the cheap tier is now a desk exercise — county parcel viewers, city zoning maps, EnviroStor, and CalFire's hazard-severity maps are all online and free. That's a real change from a decade ago, and it means there's no excuse for walking into an offer without it. What hasn't changed: none of those layers is authoritative for your specific parcel. A zoning confirmation letter with a planner's name on it is what you can act on.
What it costs to find out
Surveys run $700–$2,500 for a basic residential survey, $3,000–$8,000 for a topo/utility survey (hillside or ADU work pushes toward the top of that range), and $4,000–$10,000+ for an ALTA survey on a commercial parcel. Geotech test borings run roughly $300–$450 per boring with hand-augers for a typical 2–3 story residential project. A Phase I environmental assessment runs $2,000–$4,000; Phase II, if triggered, starts around $5,000–$7,000 and can reach six figures on a larger site. These are national going rates, not proprietary pricing — they're here so a first-time buyer knows the order of magnitude before making a single call.
The pattern: cheap checks first. A site visit, a zoning confirmation letter, and a title search rule out the worst outcomes for a few hundred dollars. ALTA, geotech, and Phase II only get ordered once the cheap ones have failed to find a reason to walk.
Before you make an offer
Evaluating a specific San Gabriel Valley parcel? Schedule a consultation for a second set of eyes on the zoning, entitlement path, and fee exposure before you're in contract.
Once you own the lot, the next decision is the fork: ADU or Ground-Up? The Two Timelines, Side by Side. For build costs after diligence clears, see what it costs to build in the San Gabriel Valley.