Why Home Inspections Miss Problems
And What You Can Do About It
No inspection catches everything. Here’s an honest look at why, and the specific steps that close most of the gaps before you close on a house.
Buyers sometimes call after closing, frustrated that something showed up a few months in that the inspection didn’t catch. I get it. You paid for an inspection specifically to find out what’s wrong with the house. When something breaks or gets discovered later, it feels like the inspection failed.
Sometimes that’s fair. Sometimes the inspector missed something they should have caught. But most of the time, the answer is more straightforward: inspections have real structural limits, and those limits aren’t secrets. They’re spelled out in the standards of practice every licensed inspector works under.
Understanding those limits helps you make better decisions during the inspection period. Not just “did the inspector find the stuff” but “did I add the right tests for this house?”
Here’s what inspections genuinely can’t do, and what actually helps.
The Fundamental Limit: It’s a Visual Inspection
A home inspection is a visual, non-invasive assessment. No holes in walls. No moving appliances. No pulling up carpet. No digging around the foundation. The inspector looks at what is visible and accessible at the time of the inspection.
That covers a lot. Roof surface condition, visible framing in attics and crawlspaces, electrical panels, plumbing fixtures and supply lines, heating and cooling equipment, interior finishes, windows and doors. A thorough inspector working a 2,000-square-foot house is looking at hundreds of components.
But the word “visible” does real work there. What’s behind a finished wall isn’t visible. What’s inside a buried drain pipe isn’t visible. What’s under a concrete slab isn’t visible. If a defect exists entirely inside a structure that can’t be disturbed, a standard inspection can’t find it.
That’s not a failure of the inspector. That’s the definition of the job. The question is what you do with that knowledge.
Access Problems: What Blocks a Good Inspection
Access matters as much as visibility. An inspector who can’t get into the crawlspace can’t inspect the crawlspace. An attic hatch blocked by shelving gets a note in the report and a “could not access” on that section.
This happens more than you’d think. Sellers leave stored items that block crawlspace hatches. Utilities occupy mechanical rooms in a way that makes full access unsafe. Built-in cabinetry covers the only access point to a plumbing chase. Heavy furniture sits against the wall where the inspector would need to look.
Read your report for “could not access” or “limited access” notes. Those aren’t boilerplate. They mean a section of the house was not fully inspected, and you should know what was skipped. If the crawlspace note is important to you, ask whether it can be re-inspected once access is cleared.
For the record: I fully enter every accessible crawlspace on every inspection. Suit, kneepads, the whole thing.
What a Standard Inspection Doesn’t Cover
Several systems and conditions fall completely outside the scope of a general home inspection. Not because inspectors don’t care about them, but because they require specialized equipment or expertise that isn’t part of the standard inspection.
Sewer lines. The inspector tests the fixtures: do the drains drain, do the toilets flush. But the lateral line from the house to the street is underground and can’t be seen. Root intrusion, pipe collapse, and “belly” conditions (sections that sag and pool water) only show up on a camera. A sewer scope is not part of the base inspection; it is arranged separately through a plumber.
Radon. You can’t see, smell, or detect radon without a test. It’s a radioactive gas that occurs naturally from uranium decay in soil, and parts of the Portland metro and SW Washington have elevated levels. A 48-hour radon test is the only way to know. It’s not included in a standard inspection. Add it.
Mold. An inspector can note visible mold or conditions that make mold likely. What they can’t do without air sampling is tell you about mold that’s hiding inside walls, under flooring, or in HVAC ductwork. If the report notes any moisture history or active moisture, consider adding an air quality test.
Oil tanks. Underground oil storage tanks (USTs) are a Portland-specific concern. If a home ever had oil heat, there may be a buried tank. A tank sweep (usually a locating service or ground-penetrating radar) is the only way to find one. The inspection might note evidence of a former oil system (an abandoned fill pipe outside, a vent pipe, an old oil filter in the basement), but the tank itself is buried and can’t be confirmed or ruled out visually.
Pest and wood-destroying organisms. A general inspection might note visible damage or evidence of infestation, but a licensed pest inspection is a separate report from a licensed company. In Oregon, pest inspections are available from separately licensed pest inspectors. Worth it on older homes or anything with a crawlspace moisture history.
What Actively Hides Problems
Not every missed issue is a matter of scope. Some things are genuinely concealed.
Cosmetic work done to sell a house is the most common. Fresh paint over moisture staining. New drywall patching over a repaired leak that may or may not actually be fixed. Carpet laid over damaged subfloor. None of these are necessarily dishonest on their own. Sellers fix things before listing. But fresh finishes can obscure the evidence that a problem existed, and visual inspection can’t always tell the difference between “repaired” and “hidden.”
Intermittent problems are another category. An inspection is a snapshot: it captures conditions on one day, at one time, in one kind of weather. A roof that leaks only in driving rain from the northwest won’t leak on a clear inspection day. A heating system that struggles in a hard freeze gets tested on a mild spring afternoon. A foundation drainage problem that shows up during a long wet stretch can look dry in August. If the problem isn’t present on inspection day, there’s nothing to find.
What I can look for is evidence of past events: water stains, efflorescence, old crack repairs, worn finishes. What I can’t do is create the conditions that reveal every intermittent problem. That’s where the seller’s disclosure helps. Oregon and Washington both require most sellers to disclose known defects, so a seller who knows the roof leaks in heavy rain is expected to say so. Read the disclosure alongside the inspection report.
Conditions that don’t always show up on a Portland-area inspection day
- Roof leaks driven by heavy, wind-driven rain, most common from October through March. An inspection during a dry stretch may show no active leak.
- Foundation drainage problems that only appear after weeks of wet weather, when soil around the foundation is saturated.
- Heating and cooling problems at temperature extremes. A test on a mild day won’t show how a system handles 20 degrees or a summer heat wave.
- Chimney leaks that appear only under specific wind-driven rain conditions.
And then there’s concealment by design. Interior wall cavities. Concrete slabs. Buried utility lines. These aren’t problems anyone hid. They’re just not reachable without destroying something, which inspections don’t do.
Real Inspection Photos
Access Limits and Hidden Repairs
Real photos from Russ's inspection reports where access or repairs limited the view.
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A refrigerator blocked this panel, so the cover could not be removed and the inside could not be inspected. -
An undersized hatch and low clearance kept parts of this crawlspace from being inspected. -
A ceiling patch with a stain, possibly from a past leak. Asking the seller for repair records is the next step.
How to Actually Reduce the Risk
Start with the right inspector. Not just licensed, but experienced and thorough. Certified Master Inspector® is a board-certified designation from the Master Inspector Certification Board. To qualify, an inspector must have at least three years in the inspection business, 1,000 or more fee-paid inspections and hours of training and education combined, completed professional education, agreement to the board’s code of ethics, and consent to periodic criminal background checks. That experience matters when an inspector has to make a judgment call about something unusual.
Add the right tests for the home. For any Portland or SW Washington home, consider a radon test and a sewer scope (arranged separately through a plumber). If there’s any moisture history in the crawlspace or attic, add mold air sampling. If there’s evidence of a former oil heating system, arrange a tank sweep. These are not expensive, relative to the cost of discovering them after closing.
Be there. Attend the inspection. Walk through with the inspector. Ask questions. You’ll understand the report better, and you’ll hear things in person that don’t always come through as clearly in writing. The walkthrough at the end of an inspection is one of the most useful 20 minutes you’ll spend in the whole buying process.
Read the report carefully, including the “could not access” sections. If something was blocked, think about whether you need to get access to that area before you close.
Where Thermal Imaging Closes the Gap
Thermal imaging shows temperature differences in surfaces that the naked eye misses. A cool spot on a wall or ceiling can point to hidden moisture. A heat leak pattern can point to missing insulation. A hot spot in a panel can point to an overloaded circuit.
I include thermal imaging on every inspection at no extra charge. It finds real things. I’ve caught active roof leaks invisible to the eye, sections of missing attic insulation that drive up heating costs, and electrical anomalies that warranted electrician follow-up.
It’s not magic, though. Thermal imaging can’t tell you what material a pipe is made of. It can’t look through concrete. It can’t assess the sewer line. It’s a powerful tool that expands what a visual inspection can see, but it doesn’t replace the specialized add-on tests.
A general inspection is thorough within its scope, but its scope has real limits. The way to reduce your risk is to add the right specialist tests for the age and type of home you’re buying, not to expect one inspection to cover everything. For most Portland homes, that means at minimum a sewer scope and a radon test.
Add-ons that matter most for Portland metro homes
- Sewer scope (arranged separately through a plumber): older clay tile and Orangeburg lines are common in pre-1960 homes. Root intrusion and line failure are not visible from above ground.
- Radon testing: Clark County, WA sits in EPA Radon Zone 1, and elevated readings turn up across the Portland metro. A 48-hour continuous monitor test, following EPA testing protocol, is $150 added to the inspection.
- Underground oil tank sweep: if any evidence of former oil heat exists, a tank sweep should be arranged before closing. Remediation costs for a leaking UST can exceed $50,000.
- Mold air sampling: crawlspace moisture is endemic in this climate. When the inspection notes active moisture or staining, air sampling tells you whether it has turned into an airborne problem.
- Pest/WDO inspection (from a licensed pest company): termites are less common here than in warmer climates, but dry rot and wood-destroying organisms are widespread. The damp PNW climate is hospitable to both.
If you want an inspection that uses thermal imaging on every visit, fully enters every accessible crawlspace, and gives you a clear picture of what to add for your specific house, schedule here. See what a buyer’s inspection covers, or check out the sample reports to see what the deliverable looks like.
Related: What a home inspector can’t inspect.
Home Inspection Limitations FAQ
