A standard home inspection in Maricopa County runs three to five hundred dollars and takes about three hours. The inspector is a generalist working visually, without dismantling anything, and the report you receive is going to contain somewhere between forty and two hundred observations. Most of them are trivial. A few of them matter enormously. And the ones that matter most are frequently not in the report at all, because they are not visible.
I do not think home inspectors are doing a bad job. I think buyers routinely misunderstand what the job is. A home inspection is a screening tool. Screening tools have a false negative rate, and the responsible response to a screening result is to order the specific tests that the screen cannot perform.
Test one — the sewer scope
A camera goes into the cleanout and runs the lateral to the municipal main. It takes about forty-five minutes and costs between one hundred fifty and three hundred dollars. You get video.
In Phoenix homes built before about 1980, the lateral is frequently cast iron or clay. Cast iron corrodes from the inside and fails at the joints. Clay fails at the joints too, and it fails at root intrusions, because tree roots find joints and grow into them for the water. Either failure mode is completely invisible from inside the house right up until the moment it is not.
Test two — the moisture survey
A moisture meter and a thermal camera, run across the building envelope, at the base of exterior walls, around every window and door, under sinks, at the water heater, and — critically — at the HVAC air handler and its condensate line. Two to four hundred dollars.
I spent thirty years working with organisms that need three things to establish: moisture, a food source, and time without disturbance. A building envelope with a persistent moisture source provides all three. The wall cavity is dark, undisturbed, and full of cellulose. That is not a metaphor. It is the same problem, and the intervention is the same: find the water and stop it.
In Arizona the persistent sources are specific and they repeat. Monsoon intrusion at a roof penetration or a failed window flashing. An HVAC condensate pan that does not fully drain and therefore holds standing water through every cooling season. A drip irrigation line run against a stem wall by a landscaper twenty years ago, keeping one section of foundation permanently damp. None of these are exotic. All of them are findable in an afternoon.
Test three — HVAC load verification
Confirm that the installed system capacity actually matches the conditioned square footage it is being asked to serve. One to two hundred fifty dollars, often folded into a service call.
This one matters disproportionately in Phoenix and it is chronically overlooked. Homes get additions. Garages get converted. Patios get enclosed. The square footage under conditioning goes up and the tonnage frequently does not. The result is a system that runs nearly continuously through July and August, and the way that gets described in a showing is "it runs a little long in the afternoon."
An undersized system in a climate like this one is not a quirk. It is a unit operating outside its design envelope, wearing out on an accelerated schedule, and it is a replacement on a clock you did not know was running. Full system replacement in this market is commonly eight to fifteen thousand dollars.
Test four — panel identification
Identify the manufacturer and model of the electrical service panel. This costs nothing beyond asking your inspector to photograph the label and the interior — but it has to actually be asked for, and it frequently is not.
Federal Pacific Stab-Lok and Zinsco panels have documented breaker failure modes. The specific concern is breakers that do not reliably trip under fault conditions, which defeats the entire purpose of having them. These panels were installed widely through the 1970s and into the early 1980s and a great many are still in service in central Phoenix.
What the four together actually cost
| Test | Typical Phoenix-area cost |
|---|---|
| Sewer scope | $150 – $300 |
| Moisture survey | $200 – $400 |
| HVAC load verification | $100 – $250 |
| Panel identification | Included, if requested |
| Total | Roughly $600 – $1,200 |
Against a seven-figure purchase that is somewhere between four and twelve hundredths of one percent. I have never had a client tell me afterward that it was not worth it, including — especially including — the ones where every test came back clean. A clean result is not a wasted test. It is a purchased certainty, and you are about to sign the largest contract of your life.
The untested assumption is the one that costs you. That was true in a laboratory and it is true in a house.
The sequencing that makes this work
All four get ordered the day the contract is accepted, not on day seven of a ten-day inspection period. Results need to arrive with enough runway that you can actually act on them — get a contractor bid, request a credit, re-trade, or walk. A finding you receive on the last afternoon of your inspection period is not leverage. It is a deadline.
That is the whole protocol. It is not clever and it is not proprietary. It is just done, every time, in the same order, whether the house looks perfect or not — particularly when the house looks perfect, because a house that shows beautifully is exactly the one where nobody thinks to check.