After looking at the installation recommendations for hardwood floors from the Wood Flooring Manufacturer’s Association, it looks to me like a lot of installation defects are not going to be visible during an inspection. The defects I’ve found most commonly are:
[ul]
[li]Gaps caused by shrinkage: flooring installed with moisture content too high.[/li][li]Floors squeaked or moved when walked on: inadequate fastening. May also be related to fasteners affected by shrinkage. May also be affected by improper installation over concrete slab.[/li][li]Moisture damage (stains or buckling)[/li][LIST]
[li]From watering plants[/li][li]Under-sink, dishwasher, or washing machine leakage.[/li][/ul]
[li]Typical wear from foot traffic over time.[/li][li]Damage from moving furniture or impact.[/li][li]Scraping from inadequate door bottom clearance.[/li][/LIST]
Anything else?
Floors that were installed at a higher moisture content than 10 to 12 percent moisture (dry lumber standard for me in the Northeast) content will cup or have raised edges. If this is uniform throughout a room, the floors were possibly installed with too high of a moisture content or under extremely humid conditions. If the damage is localized to an area of the floor, it was possible one of the items you have already listed. Flooring should be dried to the proper moisture content for installation or acclimated to a room over a period of time, under dry conditions.
I would say that cupping (raised edges) would occur if the flooring was installed in a low humidity environment and clinched tight, and later the relative humidity was elevated, thus causing expansion.
Are you talking about nailed hardwood, as in the standard 3/4 inch? Most of the time when a hardwood floor squeaks, it is not from improper nailing of the floor. It is generally from the subfloor moving up and down on the fasteners to the joist. Can sometimes be remedied from below with a shim, some glue, etc…
Buckling and cupping can be caused by moisture and temperature difference from the space below per a local manufacturer of hardwood flooring. The flooring should be in place a week prior to installation to allow acclimation to the house and conditions.
An area to pay close attention to is around doors. A lot of moisture. Both from wet feet, rain blowing in when open and from poor caulking, allowing water to enter at the jamb and threshold joint.
In February 2015, 60 minutes reported some varieties of laminate flooring manufactured in China release considerable amounts of formaldehyde gasses making them quite toxic. Would appreciate any input and/or experience anyone may share about inspecting and reporting on laminate flooring and how it may have impacted their reporting.