A home inspector spends about three hours at the property and hands you a 40-page report. That sounds thorough until you remember the limits: they can't open walls, they don't test every outlet, and they don't have to live with anything they miss. Most first-time buyers read the report like a warranty. It isn't one. What the inspection itself runs is a separate line in the buying budget, and it varies more than most buyers expect — here is how much a home inspection costs and what pushes the price up.
I've walked through a dozen used houses alongside friends who were buying, and I've missed things on my own purchases too. These twelve items slip past buyers and inspectors alike — and every one of them is something you can check yourself.
Under-sink cabinets are where water damage lives. Open every one. Look for water stains, swollen particleboard, mold spots, and that musty smell that means something has been leaking for a while. Shine the flashlight at the back panel and press the cabinet floor with your fingers — if it gives, water has been sitting there. Slow drips like these are exactly how the silent signs of a hidden plumbing leak start.
The sewer line is the expensive one. If the seller doesn't know what it's made of and the house predates 1980, assume the worst: Orangeburg pipe — basically tar paper formed into tubes, used from the 1940s to the 1970s — fails catastrophically, clay cracks and lets roots in, and cast iron rusts from the inside out. Replacing a line under a front yard runs $3,000 to $15,000 depending on depth and length. A standard inspection does not include a sewer scope. Pay the extra $200 to $400 for one; it's the best money you'll spend during due diligence.
You don't need a ladder for the roof. From the street or the far corner of the yard you can spot missing shingles, curling edges, a sagging ridge line, and dark patches that might be moss or might be rot. Check the gutters from below while you're at it — pulling away or overflowing means drainage has been neglected. A roof replacement costs five figures, and a roof on year 18 of a 20-year life can look "fine for now" right up until it isn't.
Walk the foundation perimeter outside, then look again from the basement or crawl space. Cracks wider than 1/8 inch deserve a second look, and stair-step cracks in brick or block are a red flag. Horizontal cracks are worse than vertical ones — they mean the wall is bowing under soil pressure. Water stains at the base of the walls count too: a damp basement after three dry days is a permanent drainage problem, not weather. White, chalky patches on those walls tell the same story — that residue is efflorescence on basement walls, minerals left behind as water moves through the concrete.
Grading is the most boring item on this list and the one that causes the most expensive damage over time. Stand at a corner and sight along the foundation: the ground should slope away from the house, at least 6 inches of drop over the first 10 feet. Soil sloping toward the house, or flower beds mounded against the siding, sends water straight into the basement. Downspouts should discharge at least 4 feet from the foundation — if they dump at the corner, you're looking at a future leak, and possibly a future conversation about whether the basement needs a sump pump.
Last, look up at the chimney. Missing or cracked cap, crumbling mortar between the bricks — both let water in. Check the vent pipes through the roof for rust and missing caps too. A damaged flue isn't just a leak; it's a carbon monoxide risk if combustion gases can't vent properly. Inspectors check the firebox. They don't always check the top of the chimney.
An inspector tests a representative sample of outlets, which means some never get checked. Your three-light tester reads open ground, reversed polarity, and missing neutral, and it takes seconds per outlet. Test every one you can reach, especially in older homes where a previous owner may have done their own wiring. I once found an ungrounded outlet behind a couch in a house I nearly bought — the inspector missed it because the couch was in the way.
For GFCIs, press TEST, then RESET, on each one. If TEST doesn't click or RESET won't stay in, the outlet is dead. Dead GFCIs in a house built after the 1970s usually mean the wiring was never updated, and that's a bigger electrical project than swapping a few outlets.
A window that sticks halfway isn't just annoying — it's a fire escape that doesn't escape. Open and close every window and exterior door, and feel for drafts at the edges. A door that won't latch can mean a shifted frame, which can mean foundation movement. And if the sellers have placed weatherstripping and draft stoppers with suspicious care, ask yourself what they're hiding.
Hearing the HVAC fan kick on proves almost nothing. Run the heat until the house reaches the set temperature, then do the same with the AC. Hold your thermometer at a vent. Listen for grinding, rattling, or the system cycling on and off too often. Then look at the bills: heating costs double what comparable homes pay points to a furnace limping toward replacement — by you.
Which brings up the bills themselves. A seller who won't hand over 12 months of electric, gas, and water bills is hiding something. A high water bill can mean a leaking pipe or a failing water softener; winter electric bills that spike can mean a heat pump falling back on expensive resistive backup heat. Compare against similar homes nearby. Data doesn't lie the way fresh paint does. On a pre-1978 house, that fresh paint deserves one more question — what is underneath it — and learning how to test for lead paint in an old house before anyone sands or scrapes takes five minutes and can change the whole renovation plan.
If the attic hatch is safe to peek through, bring the flashlight. Fiberglass or cellulose insulation should be at least 12 inches deep across the whole floor — less than that in a cold climate means high heating bills. Compressed patches, where someone stored boxes on top, lose their R-value. Dark spots suggest moisture or rodents, and daylight visible through the roof decking means holes.
| Item | Cost |
|---|---|
| Sewer line replacement | $3,000–$15,000, depending on depth and length |
| Sewer scope (the check that catches it) | $200–$400 as an add-on |
| Roof replacement | Five figures |
| Moisture meter (ends the guesswork) | About $30 |
No. A camera inspection of the main sewer line is an add-on, typically $200 to $400. On a pre-1980 house with unknown pipe material, it's the best money in the whole due-diligence process.
Cracks wider than 1/8 inch deserve a closer look, and direction matters: horizontal cracks are more serious than vertical ones because they signal the wall bowing under soil pressure. Stair-step cracks in brick or block are another red flag.
The three lights read the wiring faults that matter most in a quick check: open ground, reversed polarity, and missing neutral. It won't certify the whole electrical system, but it catches the outlets an inspector's sample never touched.
At least 12 inches of fiberglass or cellulose across the entire floor. Less than that in a cold climate means high heating bills, and compressed areas — where boxes were stored on top — lose R-value even if the depth looks right elsewhere.
Yes. This list supplements an inspection; it doesn't replace one. The inspector covers the big systems with training and tools you don't have. Your job is the corners the standard visit skips — every outlet, every sink cabinet, twelve months of bills.