The Pre-Close Playbook: A California Real Estate Due Diligence Checklist for Luxury Buyers

In California, once a buyer removes their contingencies, the earnest money deposit is at risk. The disclosure period is over. The physical inspection window has closed. And whatever code exposure, easement gap, or water-rights liability is on the property becomes the buyer's the day escrow closes.

The 17 days before that moment are the most consequential in the entire transaction.

Most buyers spend those 17 days on a home inspection, a pest inspection, and maybe a review of the preliminary title report. On a typical suburban tract home, that's often enough.

On a luxury property — a rural estate, a wine-country parcel, a mixed-use property, or anything with detached accessory structures, agricultural zoning, or a watershed component — it isn't. Not even close.

This is the CODE360 pre-close playbook. Five documents every luxury buyer, and every buyer's agent representing them, should demand, read, and stress-test before the contingency period closes.

1. The Seller Property Questionnaire (SPQ) — Read Every Overflow Field

The SPQ is California's mandatory disclosure form. Buyers see it. Buyers rarely read it, and buyers' agents almost never read the overflow fields.

That's a mistake.

The SPQ's overflow fields are where sellers write, in their own words, the things a checkbox can't capture. It's where you find:

• "The upper floor of the barn was converted to a dwelling unit prior to my ownership. Work was done without permits."

• "The neighboring property has a water line crossing this parcel to draw water from the creek. Line was installed without permits."

• "A creek pump was installed for landscape irrigation, without permits."

Every one of those disclosures is a code violation, an easement problem, or a water-rights exposure. On a case CODE360 recently reviewed, every one of the four major buyer issues traced back to a specific SPQ overflow field — not a checkbox, not the MLS, not the flyer.

What to do: Print the SPQ. Highlight every overflow field. For each one, ask: is this a physical condition, a documentation gap, or a legal exposure? Then route each one to the appropriate specialist — inspector, code compliance consultant, title officer, or attorney.

2. The Preliminary Title Report + the ALTA Survey — Cross-Check Every Easement

The prelim title report lists the easements of record — the utility easements, the road dedications, the recorded rights of way. It does not tell you what's physically on the property.

An ALTA survey does. An ALTA survey is a licensed surveyor's field-verified drawing showing everything on the parcel: fences, buildings, driveways, water lines, wellheads, encroachments, and — critically — how each of them relates to the recorded easements.

On a luxury property with rural or agricultural characteristics, the gap between what's on the prelim and what's on the ground is often where the money is hiding.

On the Napa County case CODE360 reviewed:

• A secondary driveway connected an accessory structure to the county road. Not listed as a recorded easement. If the driveway strayed onto the neighbor's parcel, the buyer might be dependent on a prescriptive easement claim or a neighbor's tolerance. If the neighbor sold, the driveway might not be there in five years.

• A water line crossed the parcel to serve the neighboring property. Not listed as a recorded easement. On its face, a trespass.

• The seller disclosed that "a creek pump was installed" for landscape irrigation — but no plumbing permit was ever pulled, and no water-rights filing was ever made with the State Water Resources Control Board.

None of those show up on a home inspection. All of them show up when you cross-check a prelim against an ALTA survey.

What to do: Order an updated ALTA title commitment and, on any rural or estate property, an ALTA survey. Sit them next to each other. Every line, driveway, wellhead, and structure on the survey should tie to an easement on the commitment — or be flagged.

3. The Septic Feasibility Letter — On Any Property With a Septic System

If the property is on septic (any parcel outside a sewer district — which in Napa County means most rural parcels), the single most valuable document in the disclosure packet is a septic feasibility letter from a licensed civil engineer.

The septic system's capacity is measured in "potential bedrooms" under the county's Local Agency Management Program (LAMP). Under Napa LAMP, a "potential bedroom" is any room ≥ 70 square feet meeting habitable-space and egress requirements — loft, office, sewing room, game room all count. A closet is not required to trigger the count.

That means the septic sizing question isn't "how many bedrooms are on the MLS." It's "how many rooms would the county count if we walked them through the house?"

The feasibility letter answers, in writing, whether the existing system can handle that count — or what expansion the reserve area can support.

On the CODE360 case, this document was the strongest single document in the entire 450-page packet. The engineer had confirmed feasibility for expansion to 7 bedrooms. Cost range: $25,000–$60,000. Buried on page 209. No one had flagged it for the buyers before CODE360 pulled it out.

What to do: If you're buying a property on septic, and if you're contemplating adding any habitable space (an ADU, an office conversion, a "bonus room"), ask the seller for a current septic feasibility letter from a registered civil engineer. If one doesn't exist, order one. It costs a few thousand dollars and it tells you whether the house you're planning to live in is legally supportable on the existing waste system.

4. The Building Permit History — Every Permit, Every Final, Every Gap

Every jurisdiction in California maintains a permit history for every parcel. In Napa County, that history is accessible through the online Permit Center or through a records request to the Building Division.

The permit history tells a specific story: what was built, when, under what code cycle, and whether it was finaled — meaning it passed final inspection and was closed out — or whether it remained open and expired.

A finaled permit is a legal, insurable improvement. An open or expired permit is a code enforcement liability the buyer inherits at close of escrow.

Gaps in the permit history — meaning a physical improvement exists on the property but no corresponding permit exists in the record — are unpermitted work. Under California disclosure law, the seller has a duty to disclose. Under the pre-close due diligence lens, unpermitted work is either:

• Legalize-able — often under AB 2533 for ADUs, or through a straightforward as-built permit for other improvements

• Not legalize-able — encroachment on a setback, oversize footprint, or a use the zoning doesn't allow

Either answer changes the value of the property. Neither answer is on the MLS.

What to do: Pull the full permit history for the parcel from the county. Walk the property with the permit list in hand. Every finaled permit should correspond to a real, matching improvement on the ground. Every improvement on the ground should correspond to a finaled permit. Any mismatch is a question.

5. The Written Question List to the Seller — And the Written Response

The California residential contract gives the buyer the right to ask the seller specific written questions about the property, and to receive written responses. Most buyers don't use it.

Use it.

On the CODE360 case, the buyer's agent forwarded a written list of four specific questions to the listing agent, and to CODE360, before the contingency period ran. Those four questions became the entire scope of the pre-close due diligence engagement. The answers — some drawn from the disclosure packet, some drawn from code and title research — became the negotiation record.

Written questions serve two purposes: they force the seller to answer on the record (which either produces useful information or produces silence, and both are informative), and they document the buyer's diligence for any post-close dispute.

What to do: Before the contingency period closes, sit with your agent and draft a written list of every specific question about the property. Legal use of every structure. Permit status of every improvement. Easements affecting every access point. Water source and water rights. Septic capacity. Insurance history. Send it in writing. Get the response in writing.

The Common Thread in Every California Due Diligence Checklist

The five documents above don't cost much individually. A permit history pull is a records request. An SPQ overflow review is 30 minutes of careful reading. An ALTA survey is a few thousand dollars on a rural property. A septic feasibility letter is another few thousand. A written question list is free.

Together, they are the difference between buying the property that's on the flyer and buying the property that's actually on the ground.

On a luxury transaction — where the price tag is high enough that a five-figure surprise is a rounding error to the seller but a real hit to the buyer — the pre-close playbook isn't optional. It's the diligence a prudent buyer, and a diligent buyer's agent, would run every time.

CODE360, LLC handles Pre-Close Due Diligence for luxury real estate transactions throughout Napa, Solano, and surrounding Northern California counties. If you're representing a buyer on a property with complex code, permit, or land-use exposure, reach out at codehelpnapa.com or call (707) 637-7066.