What Home Inspectors
Can’t Inspect
A standard home inspection is thorough. It’s not total. Here’s what falls outside the scope, and who to call when you need to go further.
This is not a disclaimer page. I’m not writing this to protect myself from liability. I’m writing it because buyers who understand the limits of a home inspection make better decisions.
A home inspection covers a lot of ground. Roof, attic, foundation, crawlspace, electrical, plumbing, HVAC, interior. More than 120 items. But there are things the inspector physically cannot assess, things that require different tools, lab testing, or licensed specialists. Every buyer deserves to know what those are before the inspection, not after.
Some of these gaps matter a lot in Portland specifically. Underground oil tanks, radon, sewer laterals through clay soil with mature roots overhead. This post names them all and tells you who to call for each one.
Why Limits Exist
Home inspections are visual and non-invasive. That’s the standard. The inspector does not open walls, dig in the yard, pump tanks, or take samples. The inspection documents what’s visible and accessible at the time of the visit.
That’s not a weakness in the process. Cutting into walls or pulling up flooring on every inspection would be invasive, expensive, and impractical. The visual approach, done well, reveals an enormous amount. Thermal imaging adds another layer on top of what the eye alone can see.
But some things are genuinely invisible without invasive methods or specialized equipment. A good inspector tells you exactly what those are, and recommends the right specialist when one is warranted. That’s part of the job.
Inside Walls, Ceilings, and Floors
The inspector cannot see inside finished walls. No one can without cutting into them.
What the inspector can do: identify surface stains, feel for soft spots, use a moisture meter at areas of concern, and use thermal imaging to look for temperature anomalies behind surfaces. These methods catch a lot. A water stain on a ceiling tells you there’s been moisture intrusion. A cool spot on a wall in thermal imaging suggests missing insulation or moisture behind the drywall.
What they can’t do: confirm the source of an older stain that’s now dry, identify a slow leak that hasn’t yet reached the surface, or find mold that’s growing inside the wall cavity with no visible evidence at all.
Underground Pipes and Buried Systems
Anything underground is outside the standard scope. The inspector can see where the drain lines exit the home. They can’t see what’s happening underground between the foundation and the street.
Buried pipes corrode, root-invade, offset, and collapse. In older Portland homes, clay tile is a common underground sewer material. It is brittle and prone to root intrusion. You won’t know the condition of that pipe from a visual inspection. Only a camera can tell you.
Underground Oil Storage Tanks
This is the big one for Portland buyers. Thousands of homes built before 1990 throughout Multnomah, Clackamas, Washington, and Clark counties once used oil heat. Most were converted to gas at some point. The tanks were often left in the ground, either decommissioned or simply abandoned.
A standard inspection can identify surface evidence that a tank might be present. Old fuel supply lines at the foundation. Vent pipes that no longer connect to anything. A fill cap in the driveway or near the house. These are documented. But confirming whether a tank is in the ground, and whether it has leaked, requires a tank scan and soil testing by an environmental specialist.
This is genuinely important. A leaking oil tank is an environmental liability that can cost tens of thousands of dollars to remediate. The fact that the inspector can’t confirm or rule out a buried tank doesn’t mean you ignore the question. It means you get a specialist.
Portland-Area Gaps Worth Knowing About
- Underground oil tanks are common in pre-1970 homes throughout the Portland metro. Tank scanning is done by environmental firms, not home inspectors.
- Radon is present at elevated levels in parts of Oregon and SW Washington. The only way to know is to test. Radon testing is available as an add-on for $150 when combined with the inspection.
- Clay sewer laterals are common in mid-century Portland homes. A sewer scope, arranged separately through a plumber, is recommended on every home, new construction included. Sewer lines can have defects at any age, including new construction: belly sections, crushed or disconnected pipe, debris, and root intrusion.
- Septic systems are common in Clackamas County and rural areas of Clark and Washington counties. A full septic evaluation requires a licensed septic professional with pumping equipment.
Sewer Line and Septic System
The sewer scope is a separate service, arranged through a plumber. It sends a camera through the sewer lateral from the house to the city main, showing you the condition of the pipe along the way. Root intrusion, cracks, offsets, and full collapses are all visible on camera. Nothing in the standard inspection tells you any of that.
For homes with private septic systems, the standard inspection documents what’s visible above ground. Wet areas in the drain field. Accessible tank condition. That’s it. A proper septic evaluation includes pumping the tank, inspecting the baffles, and assessing the drain field. That requires a licensed septic professional on site. If the home is on septic, get the inspection. Full stop.
Private Wells
A home on a private well is not served by a municipal water system. Trusted Home Inspections doesn’t inspect the well system: the well head, the pump, the pressure tank and controls, or any water treatment equipment. A licensed well or pump contractor checks those. Water quality is a lab test for bacteria, nitrates, and any contaminants specific to the area. In Oregon, the seller has to have the well water tested once they accept an offer, and your lender may ask for a test in either state.
The post on buying a house with a private well covers the water test, the well log, and who checks the pump.
Active Pest Infestations Beyond Visual Evidence
The inspector looks for visible signs of wood-destroying pests: frass (insect waste), shelter tubes from termites, soft or damaged wood, and conditions that attract pests. What they can’t detect is an active colony living inside a wall or in an inaccessible space where no visible evidence has reached the surface yet.
In Oregon, a licensed pest inspector can run a separate pest and dry-rot inspection. It produces a formal Wood Destroying Organism report. For any home with moisture issues, wood-to-soil contact, or conditions that favor infestation, it’s worth booking separately.
Pool and Spa
A pool is not part of the standard home inspection. If the property has an in-ground pool or in-ground spa, a pool inspection is available as an add-on for $295 when combined with the main inspection. That covers the pool structure, equipment, plumbing, and electrical.
Free-standing hot tubs are not included. If you’re buying a home with a hot tub that conveys with the sale, ask the sellers directly about its condition and maintenance history. Portable hot tubs are personal property, not a permanent structure, and are not part of the home inspection scope.
Chimney Interior
The inspector checks the visible portions of the chimney: exterior masonry or siding, the firebox, the damper, and the flue cap. The inside of the flue, up in the dark where the liner lives, requires a chimney camera. CSIA-certified chimney sweeps do that inspection. If the home has a wood-burning fireplace or a gas insert with an older clay tile liner, a Level 2 chimney inspection before closing is worth considering.
Real Inspection Photos
Where a Visual Inspection Stops
Real photos from Russ's inspection reports showing the edge of what can be seen.
-
Damage was clear here, but the meter read dry that day. A stain alone cannot show whether the leak inside the wall is fixed. -
A cleanout is where the drain line can be seen from the house. Past this point the pipe is buried, so a sewer scope is the way to check it. -
An unlined flue seen from the top. The rest of the flue needs a camera inspection by a chimney sweep.
When to Get a Specialist
The inspection report will tell you what was found and where a specialist evaluation is warranted. Here’s a quick reference for the most common situations in Portland-area homes.
| Sewer line condition | Sewer scope through a plumber (arranged separately) | Separate company |
| Radon gas levels | Radon testing (add-on) | $150 with inspection |
| Mold air quality | Mold air quality testing (add-on) | $245 with inspection |
| Underground oil tank | Environmental specialist, tank scan + soil test | Separate company |
| Septic system function | Licensed septic professional with pumping equipment | Separate company |
| Private well system and water quality | Licensed well or pump contractor, accredited water lab | Separate company |
| Pool and in-ground spa | Pool inspection (add-on) | $295 with inspection |
| Chimney flue interior | CSIA-certified chimney sweep, Level 2 inspection | Separate company |
| Active pest infestation | Licensed pest inspector (separate WDO report in Oregon) | Separate company |
| Structural concerns beyond visible | Licensed structural engineer | Separate company |
A home inspection is the starting point. The inspector documents conditions, flags concerns, and tells you exactly where to go deeper. Knowing the limits isn’t a reason to worry. It’s a reason to ask the right follow-up questions. Book the specialists the report recommends. That’s how you walk into closing with fewer surprises.
If you want to see what a completed inspection report looks like, including how findings are documented and specialist referrals are noted, take a look at the sample reports on the site. Or if you’re ready to schedule, book online here.
Inspection Limits FAQ
