The illustration above shows the difference between an S-trap and a P-trap. S-traps are not permitted due to siphoning problems. Complements of www.nachi.org

Truss Uplift

A home inspector may observe during a home inspection a crack in the corner of an interior ceiling made of drywall. The crack may be at the top of the wall, and it may appear very thin or narrow (a hairline crack).

Unvented Crawlspaces

In most climate zones, conditioned crawlspaces perform better than vented crawlspaces in terms of safety, health, comfort, durability, and energy consumption. Research has demonstrated how these conditioned crawlspaces also do not cost more to construct than vented crawlspaces. Crawlspace venting is a widely accepted business practice across the U.S. However, in humid climates, the warm humid air entering the crawlspace is more likely to condense on crawlspace framing than it will to help dry out the crawlspace. This is because the outside air can often have a dew point that is higher than the interior crawlspace framing surface temperature. As evidence, existing vented crawlspaces have experienced serious moisture and mold problems, costing builders and homeowners significant resources to repair.

Notches in the middle third of a floor joist are not permitted. Holes are not permitted to be located within 2 inches of the top or bottom edge of a floor joist. The maximum depth of a notch in a floor joist (that is not in the middle third of the joist) is the actual depth of the joist divided by 6. The maximum diameter of a bored hole through a floor joist (that is not in the middle third of the joist) is the actual depth of the joist divided by 3.

Crawlspaces

Access openings must be a minimum of 18 inches high by 24 inches wide. Access to all under-floor spaces must be provided with access openings through the floor not smaller than 18 inches by 24 inches (457 mm by 610 mm).

Check for downspouts diverters not discharging water far enough away from the house. Check floor lawn irrigation systems spraying water against the house foundation, and check for gardens or planters that are up against the house. These may be causing wet soil pressure problems for the structure.

Hydrostatic pressure refers to the pressures caused by water pushing against slabs and foundations, particularly underground concrete block or poured concrete walls of foundation and crawlspaces. Water is dense and weighs about 60 lbs. per cubic foot of volume and is therefore capable of generating immense hydrostatic pressure on anything that restricts its natural movement or flow.

A crack that forms a V-shape may indicate heaving. The illustration above shows a V-shape open crack in a foundation wall indicating heaving from the ground under the foundation footing. The ground in the illustration is expanding and pushing upward on the footing and foundation, causing a crack. This observation by a home inspector would be reported as a major structural concern and defect with correction and further evaluation & repair by a licensed foundation contractor or structural engineer

nearby vegetation

The inspector is required to report vegetation growing near the home according to the Home Inspection Standards of Practice. The home inspector should note the existence of any trees near the home, because the roots may affect the foundation or underground drainage pipes. Plants growing next to a house could raise the soil level too high against the foundation.

steep slope

The home inspector should note if a home is on a steep slope and, therefore, subject to erosion or movement. The maximum slope of a lot should be roughly 1-in-2.