Scope and limits
What a home inspection actually covers, and what it does not
A home inspection is a visual, non-invasive examination of the readily accessible parts of a house, performed on one day, by one person, without taking anything apart. Almost every disappointment buyers have with an inspection traces back to a clause in that sentence rather than to the inspector.
Two documents define the job in most of the United States: the Standard of Practice published by the American Society of Home Inspectors (ASHI) and the Standards of Practice published by InterNACHI. Many state licensing boards adopt one of them, or write their own closely modeled on them. If you want to know what you are buying when you pay for an inspection, these are the documents to read, and this page is a plain-language walk through what they say.
The definition does most of the work
ASHI defines inspect as the process of examining readily accessible systems and components by applying the standard, operating normal operating controls, and opening readily openable access panels. It defines readily accessible as available for visual inspection without requiring moving of personal property, dismantling, destructive measures, or actions that will likely involve risk to persons or property.
InterNACHI states the same idea from the other direction: a home inspection is a non-invasive, visual examination of the accessible areas of a residential property, based on observations made on the day of the inspection, and it will not reveal every issue that exists or ever could exist.
Three words to hold on to. Visual: if it cannot be seen, it is not inspected. Non-invasive: nothing gets opened up, cut into, or taken apart. Readily accessible: a wall of stored boxes, a locked crawlspace hatch, or snow on the roof puts whatever is behind it out of scope. An inspector who moves the seller's furniture to look behind it is going beyond the standard, not meeting it.
InterNACHI frames the target of the inspection as the material defect, which it defines as a specific issue with a system or component that may have a significant adverse impact on the value of the property, or that poses an unreasonable risk to people. That is a deliberately higher bar than "anything wrong with the house." A scuffed baseboard is a flaw; it is not a material defect.
The systems that are covered
Both standards organize the required scope into the same ten areas. This is the checklist your report should broadly follow.
| System | What the standards require |
|---|---|
| Structure | Foundation and framing, including visible basement and crawl space conditions |
| Exterior | Wall coverings, exterior doors, decks and porches, eaves, and site drainage around the building |
| Roofing | Roof covering materials, drainage systems such as gutters, flashings, and roof penetrations |
| Plumbing | Water supply, drain, waste and vent piping, fixtures, and water heating equipment |
| Electrical | Service entrance, panelboards, conductors, receptacles, and installed safety devices such as detectors |
| Heating | Permanently installed heating equipment, its venting, and the distribution system, operated by normal controls |
| Cooling | Central cooling equipment and distribution, operated by normal controls |
| Interior | Walls, floors, ceilings, stairs, railings, windows and interior doors, and garage doors |
| Insulation and ventilation | Insulation in unfinished spaces, attic and crawl space ventilation, and exhaust systems |
| Fireplaces and fuel-burning appliances | Accessible portions of fireplaces, stoves and inserts, dampers, and chimneys |
Note the recurring phrase "operated by normal controls." The inspector turns the heat on at the thermostat and watches what happens. Nobody performs a combustion analysis, measures refrigerant charge, or load-tests the panel. Those are the tasks of specialist trades, and they are outside the standard on purpose.
The exclusions buyers are most surprised by
The exclusions are where the gap between expectation and standard is widest. Under ASHI's general limitations and exclusions, inspectors are not required to determine the condition of systems and components that are not readily accessible, the remaining life expectancy of systems and components, or compliance of systems and components with past and present requirements and guidelines. They are also not required to determine the strength, adequacy, or efficiency of a system, nor the cause of a deficiency they observe.
The ASHI standard also excludes the presence of plants, animals and other life forms and substances that may be hazardous or harmful to humans, including wood destroying organisms, molds and mold-like substances, and it excludes environmental hazards in building materials, soil, water and air. InterNACHI is equally explicit: its inspectors are not required to determine the presence of evidence of rodents, birds, bats, animals, insects, or other pests; the presence of mold, mildew or fungus; the existence of environmental hazards including lead paint, asbestos or toxic drywall; or the presence of airborne hazards including radon.
Then there are specific systems that both standards carve out entirely. Under the ASHI standard, inspectors are not required to inspect underground items including underground storage tanks; manual and automatic fire extinguishing and sprinkler systems and landscape irrigation systems; wells, well pumps and water storage-related equipment; water conditioning systems; septic and other sewage disposal systems; and security systems. InterNACHI likewise excludes determining code compliance, service life expectancy, insurability, suitability for use, and repair costs.
| Commonly assumed to be included | Actually | How it is usually handled |
|---|---|---|
| Radon | Excluded from both standards | Separate radon measurement, ordered as an add-on |
| Mold | Excluded from both standards | Separate assessment and sampling by a specialist |
| Termites and other pests | Excluded from both standards | Separate wood-destroying-organism inspection, often lender-required |
| Septic system | Named exclusion in the ASHI standard | Separate septic evaluation; in Massachusetts, a Title 5 inspection |
| Private well and water quality | Named exclusion in the ASHI standard | Separate water testing and well evaluation |
| Buried oil tanks | Named exclusion in the ASHI standard | Tank sweep by a specialist contractor |
| Lawn sprinklers, security systems | Named exclusions in the ASHI standard | Vendor service call, or seller demonstration before closing |
| "Is this up to code?" | Excluded from both standards | Local building department; an inspection is not a code compliance review |
| "How many years left on the roof?" | Excluded from both standards | Roofing contractor estimate, and even then it is a judgment |
None of this means an inspector will stay silent about a stain that looks like mold or a mud tube that looks like termites. Most will note what they see and recommend a specialist. The distinction is between observing something in passing and being obligated to find it, and only the second one is what you have paid for.
Four assumptions worth correcting before inspection day
"The inspection is a warranty on the house"
It is a report on observable condition on a single day. InterNACHI says so directly: the inspection is based on observations made on the day of the inspection and will not reveal every issue that exists or ever could exist. A problem that appears three months later is not automatically a missed defect.
"They will find everything"
Neither standard requires a technically exhaustive inspection, and ASHI expressly excludes concealed conditions and latent defects. A failing pipe inside a finished wall is invisible to a visual, non-invasive examination. So is the condition of the underside of a roof deck under insulation, or a foundation crack behind a finished basement wall.
"Everything got tested"
Systems are operated by their normal controls. Under the ASHI standard, inspectors are not required to dismantle systems and components except where the standard explicitly requires it. Nothing is disassembled, and the standard does not ask the inspector to judge whether a system is adequately sized or efficient.
"If it is not in the report, it is fine"
If it was not accessible, it was not inspected, and a good report will say so. Read the limitations section of your report as carefully as the findings: blocked attic hatch, snow-covered roof, furniture against a wall, utilities shut off, crawl space too low to enter. Each one is a piece of the house that was never examined, and each is an opportunity to ask for a re-visit before closing.
How to use the standard to your advantage
- Read the standard your inspector works to before you book. Ask which one governs the work: ASHI, InterNACHI, or a state standard. In Massachusetts, home inspectors are licensed by the Board of Registration of Home Inspectors, and the state has its own regulations and required scope.
- Order the ancillary services separately and early. Radon, pests, septic, well water, and buried tanks are the five that most often matter, and none of them are part of the base inspection. Book them alongside the inspection rather than after it, so results arrive inside your contingency window.
- Attend the inspection. The narrative you get walking the house is more useful than the report, and it is the moment to ask what was not accessible and why.
- Treat the limitations list as a to-do list. Anything the inspector could not reach is unknown, not fine.
Sources
- Standard of Practice, American Society of Home Inspectors (ASHI). Definitions of "inspect" and "readily accessible", required systems and components, and the general limitations and exclusions.
- Standards of Practice, International Association of Certified Home Inspectors (InterNACHI). Definition of a home inspection and of a material defect, scope by system, and general exclusions.
- Board of Registration of Home Inspectors, Commonwealth of Massachusetts. Licensing of home inspectors in Massachusetts.
Related
- Outline of an inspection, from the ALLSAFE archive: how one Massachusetts practice described its own on-site coverage.
- The final report, from the ALLSAFE archive.
- The full ALLSAFE archive index.