Before I walk into a house I look at one number: the year it was built. That number tells me what materials were standard at the time, which of those materials have known service lives, and therefore what I should be looking for before I look at anything else. This is materials science, and the useful thing about materials science is that it is knowable in advance rather than discovered at the worst moment.
To be very clear about what follows: none of these are defects. A 1962 house is not a bad house. A build year is a hypothesis about what to check, and every item below is verifiable during an inspection period for very little money.
Pre-1950 — the historic districts
Willo, Encanto-Palmcroft, Alvarado, F.Q. Story. The oldest housing stock in Phoenix and, in my opinion, some of the best. It also has the longest list of things to verify.
- Galvanized steel supply lines. Service life is roughly fifty to seventy years and these are past it. They corrode from the inside, which shows up as reduced flow and rust-tinted water at first draw. Repiping a small home is commonly eight to fifteen thousand dollars.
- Knob-and-tube remnants. Rarely the whole house at this point, but frequently a circuit or two surviving in an attic. Many insurers will not write over active knob-and-tube.
- Cast iron waste lines at joint-failure age. See the sewer scope.
- Original plaster over wood lath. Beautiful, and genuinely worth preserving. Also brittle, and expensive to repair correctly rather than patch badly.
- Crawlspace moisture. These homes have crawlspaces, and crawlspaces in a monsoon climate hold water. This is where I moisture-map without exception.
1950 – 1970 — the ranch belt
Arcadia originals, much of central Phoenix, early Scottsdale. Slab-on-grade construction, generous lots, and the era where Phoenix built the housing stock that defines it.
- Cast iron and clay sewer laterals — the single highest-value thing to scope in this era.
- Original single-pane aluminum windows. Thermally terrible in this climate and a meaningful, ongoing line item on the cooling bill.
- Undersized electrical service — 60 or 100 amp panels that were adequate for a 1958 household and are not adequate for a 2026 one.
- Slab-on-grade poured without a vapor barrier, which was normal practice. Watch for moisture migration at the slab edge and under flooring.
1970 – 1990 — the era with the two big ones
McCormick Ranch, much of the Biltmore patio-home stock, north-central. This era carries the two failure modes I care most about, and both are cheap to check.
- Aluminum branch wiring in some 1965–1975 stock. Not inherently dangerous, but requires proper terminations that were frequently not used.
- Original evaporative-to-refrigerated cooling conversions, sometimes done without upgrading the ductwork or the electrical to match.
1990 – 2005 — the stucco years
North Scottsdale expansion, the far valley, and a great deal of infill. Envelopes are better. The specific concern shifts to how they were detailed.
- EIFS synthetic stucco applied without the drainage plane behind it. Correctly detailed EIFS is fine. Barrier EIFS with no way for incidental water to escape traps that water against sheathing. This is findable with a moisture meter in an hour.
- First-generation polybutylene still in service at the early end of this range.
- Early low-E dual-pane windows now reaching seal-failure age — visible as permanent fogging between panes.
- Original HVAC now comfortably past design life, whatever the seller says about how well it runs.
2005 and newer
Generally sound envelopes and generally modern mechanicals. The concerns here are less about era-standard materials and more about individual execution.
- Post-2008 cost pressure showing up in flashing details, particularly at roof-to-wall transitions.
- Builder-grade water heaters specified without regard to local water hardness, which shortens their life considerably. See the water chemistry note.
- Additions and conversions permitted after the fact — or never permitted at all. Pull the permit history. It is a public record and it is free.
How to actually use this
Look up the build year before the showing. Take the corresponding list. Verify each item during the inspection period with a specific instrument or a specific document. Price whatever you find, with a contractor number rather than an estimate. Then decide.
That is the entire method. Its value is not that any individual item on these lists is obscure — most inspectors know all of it. Its value is that it gets done deliberately and completely rather than depending on whether it happened to catch someone’s eye on a Tuesday afternoon.