Short answer: a general home inspection does not check the sewer line, does not test for radon, does not run a camera up the chimney, does not test for wood-destroying insects, and does not test for mold. It checks structure, systems, roof, and a broad visual sweep — full stop. Anything more specific than that is an opt-in add-on you have to know exists, ask for by name, and pay for separately, usually somewhere in the $100–$700 range per item depending on which one. This is the menu: what each add-on actually covers, what it costs, and the situational trigger that tells you whether it's worth booking during your inspection contingency window.

Why your "home inspection" doesn't already cover this

A standard general home inspection follows a fairly narrow scope — something like the InterNACHI Standards of Practice — that's built around visual, non-invasive checks of the roof, foundation, electrical, plumbing, HVAC, and structure. It's genuinely useful, and it's the right baseline for every purchase (see our separate piece on what actually makes a home inspector worth hiring). But "visual and non-invasive" is the operative phrase — an inspector isn't running a camera down your sewer line, testing indoor air for radioactive gas, or swabbing for mold spores as part of the standard walkthrough. Those require different tools, different licenses in a lot of states, and separate line items on the invoice.

Nobody hands you this list at closing. Real estate agents mention some of these in passing, sometimes; sellers definitely aren't volunteering "hey, you might want to test for radon." So here's the full mental map, roughly in order of "most people should at least consider this" to "situational, ask yourself if it applies."

Radon testing

What it is: A test — short-term (2–7 days) or long-term (90+ days) — that measures radon, a naturally occurring radioactive gas that seeps up from soil and rock into a home through foundation cracks, sump pits, and gaps around pipes. It's colorless, odorless, and the second-leading cause of lung cancer in the U.S. after smoking, per the EPA.

Cost: Professional testing runs roughly $125–$400, averaging around $250; DIY kits run $10–$50 but are less reliable for a real estate transaction where you often need a certified tester's results, per HomeGuide's 2026 cost data.

When it's worth it: The EPA's blunt position is that every home should be tested, regardless of location — elevated radon has turned up in all three of its risk zones, not just the high-risk one. That said, the EPA's Map of Radon Zones sorts every U.S. county into one of three zones, with Zone 1 (red) meaning average indoor levels are predicted above the action level of 4 pCi/L. If your target county is Zone 1, treat radon testing as close to mandatory. If it's Zone 2 or 3, it's still cheap enough that most buyers add it anyway rather than gamble — a "why wouldn't you" line item, not a "only if" one. Basements and slab-on-grade homes are generally more exposed than homes with a raised foundation, since the gas enters through ground contact. There's a full separate piece on this site going deeper on radon specifically — this is just the "should I add this line item" version.

Sewer scope

What it is: A camera run through the sewer lateral (the pipe connecting the house to the municipal main or septic tank) via the cleanout, checking for cracks, bellies, offset joints, and root intrusion.

Cost: Roughly $100–$500, per Rocket Mortgage's 2026 cost breakdown — cheap relative to the failure mode it catches, which is a five-figure pipe replacement invisible from a normal walkthrough.

When it's worth it: Older homes (pre-1970s especially, when clay, cast iron, and Orangeburg pipe were common) and any property with mature trees near the house or the likely path of the sewer line. We've got a full dedicated piece on this exact intersection — WTF Is a Sewer Scope, and Does That Gorgeous Oak Tree Need One? — walking through how roots actually get into a pipe and what repair costs look like if they have. Short version here: old house + big tree + unknown pipe material is the trigger. A brand-new PVC line under a treeless yard is a low-priority add.

Chimney inspection

What it is: An inspection of the chimney and flue, done in tiers defined by the National Fire Protection Association (NFPA 211) standard:

  • Level 1 — a basic visual check of readily accessible parts, $100–$250, appropriate for a chimney in regular, unchanged use.
  • Level 2 — a full Level 1 assessment plus a video scan of the interior flue and hard-to-reach areas, $250–$600. This is the level industry cost guides recommend specifically for a home purchase, since you're evaluating a system with unknown history.
  • Level 3 — the most invasive tier, sometimes involving removing drywall, brick, or the chimney cap to investigate a specific concern found at Level 2, $900–$5,000. Only needed if Level 2 turns up a real problem.

When it's worth it: Any home with a wood-burning fireplace or an older masonry chimney, especially if the seller can't produce a recent sweep/inspection record or the house has sat with an unused chimney for a while (animals nesting, cap deterioration, and creosote buildup don't announce themselves from the street). If you don't plan to ever use the fireplace, this drops way down the priority list — but note that "never using it" doesn't fully eliminate the risk, since a compromised flue can still be a structural or moisture-intrusion issue even unlit.

Pest / termite (WDO/WDI) inspection

What it is: A wood-destroying organism (WDO) or wood-destroying insect (WDI) inspection — a licensed pest inspector checks for termites, carpenter ants, wood-boring beetles, and existing damage, and issues a report (often the standardized NPMA-33 form) that lenders sometimes require directly.

Cost: For a real estate transaction, typically $75–$325; VA-loan-required inspections specifically run closer to $100–$200, per HomeGuide and Veterans United's breakdown of VA requirements.

When it's worth it: This is one of the few on this list that can be non-optional depending on your loan and location. The VA requires a WDI inspection in more than 30 states rated moderate-to-heavy or very-heavy termite risk — mostly the Southeast, South, and Midwest — and it's discretionary elsewhere unless the appraiser flags a concern. FHA and conventional loans don't universally require it the way VA does, but check your specific lender and state. Regionally: the Southeast (Florida, Georgia, the Carolinas, Alabama, Mississippi, Louisiana) and Southwest (Texas, Arizona, southern California) carry the highest termite activity in the country. If you're buying there, this isn't really an "add-on" decision — budget for it as a default line item.

Mold inspection

What it is: A visual assessment plus, often, air or surface sampling (spores are counted and compared to an outdoor baseline) to determine whether mold is present, where, and how extensive.

Cost: A full inspection runs roughly $300–$650 on average (up to $1,000+ for a larger home or heavier contamination); individual sample tests run $50–$350 each depending on method (air, surface, or bulk sampling), per HomeGuide's 2026 data.

When it's worth it: Not every house needs this — mold testing without a specific reason to suspect a problem is one of the more skippable items here. The real trigger is evidence, not paranoia: a musty smell, visible spotting, a disclosure or inspection report mentioning past water intrusion, a basement that's clearly been damp, or a house that's sat vacant for a long stretch (stagnant, unventilated air is a mold accelerant). We've got a separate walkthrough on how to spot water damage, mold, and foundation cracks yourself during a showing — use that as your free first-pass filter, and reach for a paid mold inspection only if something there actually raises a flag. Note also that the EPA generally treats mold patches under about 10 square feet as a DIY cleaning problem, not a remediation-company problem — so a positive finding doesn't automatically mean a giant bill, it just means you now know what you're dealing with before you own it.

Honorable mentions (less universal, still worth knowing exist)

A few others that come up often enough to name, without needing a full section each:

  • Septic inspection — if the home isn't on municipal sewer, this is arguably not optional at all; budget $200–$900. (We've got a separate primer on how septic systems work if you're new to this.)
  • Well water testing — for a home on a private well, testing for bacteria, nitrates, and contaminants specific to the area; often bundled with septic inspections in rural sales.
  • Asbestos and lead-based paint testing — mainly relevant for homes built before 1978 (lead paint) or before the 1980s (asbestos in insulation, flooring, or siding); roughly $300–$700 each.
  • Structural engineer evaluation — not a standard add-on you book proactively, but the right escalation if your general inspector flags foundation cracking, sloping floors, or sticking doors. Covered in more depth in our water damage/mold/foundation cracks piece.
  • Pool/spa inspection — if the home has one, $200–$500 to check equipment, structure, and safety compliance separately from the general inspector's cursory look.

So how many should you actually add?

Nobody's budget or inspection contingency window can absorb every item on this list for every house — and most houses don't need all of them. A reasonable way to triage:

  1. Start with the general inspection. That's non-negotiable and it's the thing that tells you where to look closer.
  2. Add radon almost everywhere, because it's cheap, fast, and the downside (undetected lung-cancer-risk gas) is disproportionate to the cost.
  3. Add whatever your region and loan type effectively require — pest/termite in high-risk states or with a VA loan, septic and well if the house has them.
  4. Add whatever the house's specific history suggests — sewer scope for an older home with big trees nearby, chimney Level 2 for a fireplace with no recent sweep record, mold testing if you smell or see something during the walkthrough.
  5. Treat the rest as situational, not default.

None of these are individually expensive — the total for a genuinely thorough add-on package (general inspection plus radon, sewer scope, and a pest inspection, say) usually lands somewhere in the $700–$1,500 range depending on market. Against a home purchase in the hundreds of thousands, that's rounding error. Against a surprise five-figure sewer line replacement or a lung-cancer risk you didn't know about, it's one of the cheapest insurance policies in the entire homebuying process.

Sources

As of August 16, 2026. Costs are national averages and vary significantly by market — get local quotes before budgeting. Specific loan-type inspection requirements (VA, FHA) change periodically; verify current rules with your lender before relying on them. [State-by-state VA discretionary/mandatory list above summarized from a single source — confirm against current VA guidance before relying on it.]