Inspection scope
What home inspectors miss most often
The question people really ask is not "what do inspectors miss" but "what will I discover after closing that the inspection did not catch." Those are different questions. Some defects are missed because an inspector made an error. Others are missed because the standards of practice do not require the inspector to look for them in the first place. Both categories surprise buyers, but the fix for each is different: one is a better inspector, the other is a better understanding of what an inspection is.
The most reliable way to know what inspectors miss is to look at what their insurance companies pay claims on. According to InspectorPro Insurance, which has handled inspector errors-and-omissions claims for more than a decade, water damage generates nearly half of all E&O claims filed against home inspectors in the past three years (inspectorproinsurance.com). Roof damage claims rank second, and many of those are also water-related: a roof leak that was present on inspection day but not caught.
What the claims data says
InspectorPro Insurance classifies E&O claims into three categories (inspectorproinsurance.com):
- Neglect: the inspector failed to find or report a defect that was visible and within scope. This is the classic "miss."
- Failure to perform: the inspector did not meet the terms of the pre-inspection agreement. This is a scope dispute, not a detection failure.
- Bad advice: the inspector reported a defect but gave an inappropriate recommendation about it. The defect was found; the guidance was wrong.
Only the first category is a true miss. The other two are process and judgment errors that happen even when the inspector sees the problem.
Within the neglect category, the specific defects that generate the most claims are overwhelmingly moisture-related. One inspector interviewed by InspectorPro estimated that 8 out of every 10 homes inspected have water intrusion or water damage issues of some kind (inspectorproinsurance.com). Not all of those are reportable defects, but the scale of the problem explains why water is where the misses concentrate.
The five areas where misses concentrate
Based on the claims data that is public, and on what the standards say about each system, these are the areas where an inspection is most likely to leave something unreported:
1. Water intrusion and moisture damage
Nearly half of all E&O claims fall here, according to InspectorPro Insurance. The problem is structural: a home inspection is a visual, non-invasive examination. Water damage behind finished walls, under floors, or in enclosed crawl spaces is often invisible on inspection day. The standards explicitly do not require an inspector to move personal property, open walls, or use moisture meters (though many do voluntarily). A dry stain on a ceiling might be old and repaired, or active and leaking the next rain. The inspector is required to report what is visible, not what is behind the drywall.
2. Roof condition
Roof damage ranks second in the InspectorPro claims data. InterNACHI's Standards of Practice say the inspector is not required to walk on a roof (nachi.org). Many inspectors inspect the roof from the ground or from the eave line with binoculars. Subtle issues, such as a lifted shingle, deteriorated flashing around a chimney, or a soft spot indicating sheathing rot, can be invisible from that distance. The roof is also the system most affected by weather timing: a roof that appeared sound on a dry Tuesday may leak on Saturday.
3. Electrical defects
The standards require an inspector to examine the service entrance, the main panel, and a representative number of outlets and switches. They do not require the inspector to remove panel covers in all cases, test every outlet, measure amperage or voltage, or verify that the system meets current code. According to ASHI's Standard of Practice, inspectors are not required to "determine the adequacy of the system" or "determine compliance with applicable codes" (homeinspector.org). The practical gap: an ungrounded outlet behind furniture, a double-tapped breaker behind a panel cover the inspector did not remove, or aluminum branch wiring that functions normally on inspection day but presents a fire risk over time.
4. Plumbing and drainage
The standards require running water and checking fixtures for functional flow. They do not require testing shower pans for leaks (InterNACHI SOP, nachi.org), inspecting the sewer line with a camera, determining water quality, or evaluating the septic system. A slow drain may be a clog; it may also be a bellied sewer line that costs thousands to repair. The inspector has no way to tell without a scope, and the standards do not require one.
5. HVAC systems at the wrong time of year
Both ASHI and InterNACHI state that an inspector is not required to operate a system that has been shut down or is not safely operable. In practice, this means the air conditioner may not be tested in winter, and the furnace may not be tested in summer (operating an AC when ambient temperature is below roughly 60°F risks compressor damage). A buyer who closes in March may not discover a failed compressor until June. According to ASHI, the inspector is also not required to "determine the adequacy of combustion air" or "determine the uniformity of the supply of conditioned air to the various rooms" (homeinspector.org). The system runs; whether it heats or cools evenly throughout the house is outside scope.
What the standards explicitly exclude
Many things buyers assume are checked are not part of a standard home inspection at all. Both major professional associations publish their exclusion lists. Here is a combined summary of the most consequential ones:
| Excluded item | Standard that excludes it | Why it matters |
|---|---|---|
| Mold, lead paint, asbestos, radon | Both ASHI and InterNACHI | Environmental hazards require specialized testing. An inspector may note conditions favorable to mold but is not required to test for it. |
| Pest and wood-destroying organisms | Both (separate specialty) | Termite inspections are a separate engagement, often required by lenders but not part of the home inspection. |
| Sewer scope / septic evaluation | Both | Sewer line failures can cost $5,000 to $25,000. A separate camera inspection is the only way to find them before closing. |
| Swimming pool and spa | InterNACHI SOP | Pool equipment, liners, and structural integrity are outside scope unless added as a separate service. |
| Chimney and flue interiors | InterNACHI SOP | A chimney may look fine from outside while the flue liner is cracked or missing. A Level 2 chimney inspection is a separate engagement. |
| Smoke and CO detector testing | ASHI SOP; InterNACHI SOP excludes testing | An inspector notes their presence but is not required to test whether they function. InterNACHI explicitly excludes "testing smoke and carbon monoxide devices and alarms." |
| Code compliance | Both ASHI and InterNACHI | A home inspection is not a code inspection. The inspector reports defects, not violations. |
| Cosmetic condition | Both | Scratches, dents, paint condition, and carpet stains are explicitly outside scope. |
| Remaining useful life | Both | The inspector is not required to estimate how many years a roof, furnace, or water heater has left. |
The full Standards of Practice are published by InterNACHI and ASHI and are worth reading before hiring an inspector. They are short, written in plain language, and they will change what you expect from the report.
How to fill the gaps
A standard home inspection is a starting point, not a finish line. For the exclusions above, the gap-fillers are separate, specialized engagements:
- Sewer scope: a plumber runs a camera down the main drain line. Prices vary widely by market. Worth doing on any home older than 30 years.
- Radon test: a 48-hour canister or continuous monitor. Many inspectors offer this as an add-on; some states require it at sale.
- Pest inspection (WDO/WDI): a licensed pest inspector checks for termites, carpenter ants, and wood rot. Required by most lenders.
- Chimney inspection: a Level 2 inspection with a camera is the standard for a real estate transaction. Industry guidance recommends a Level 2 inspection whenever a property changes hands.
- Moisture and thermal imaging: some inspectors carry infrared cameras and moisture meters as part of their standard kit. If yours does not, ask. These tools can reveal moisture behind walls that a visual check cannot.
- Photo-based condition documentation: tools like RapidEye use AI to analyze property photos and video for damage and condition issues. They do not replace a licensed inspector, but they can catch damage and condition issues that a visual walkthrough misses, whether on a first look or a repeat visit.
The honest answer
Home inspectors miss water damage more than anything else, because water damage hides behind the surfaces the standards say not to open. Roof problems rank second for the same reason: the evidence is often only visible from on the roof, and the standards do not require the inspector to go up there. Everything else, including the environmental hazards, the sewer, the chimney interior, and the pest damage, is not a miss at all. It is an exclusion. The inspector did not check because the standards did not ask them to.
Knowing the difference before you hire an inspector is the single most useful thing a buyer can do. The inspection report will be more useful if you already know what it does not cover.
Related on this site: What a home inspection actually covers, and what it does not.
Sources
- InspectorPro Insurance, water damage claims data (inspectorproinsurance.com).
- InspectorPro Insurance, roof damage claims data (inspectorproinsurance.com).
- InspectorPro Insurance, E&O claims categories and examples (inspectorproinsurance.com).
- InterNACHI, Standards of Practice (nachi.org).
- ASHI, Standard of Practice (homeinspector.org).