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).
Where physical entry is impossible, use a powerful flashlight. A digital camera with a zoom lens works well.
Frost heave may occur during the winter after the crawlspace walls are insulated because the lack of insulation was keeping the soil near the building warm enough to prevent freezing.
The grade (soil) should be at least 18 inches below the bottom of the floor joists, and 12 inches below beams. However, some codes require 24 inches below the bottom of the floor joists and 18 inches below the beams so that inspectors and contractors can enter. Most codes require 18-inch-high access openings. So, if a beam is lower than that, the inspector should note it in his report as a restriction. Columns and posts must be constrained to their footings, must be a minimum of 4x4, must be connected to girders with approved hardware, and be pressure-treated if closer than 8 inches to the soil. Wood siding and sill plates should be at least 6 to 8 inches above grade. Most standards say 8 inches.
Piers made of hollow concrete block or cinder block should be installed with the hollow channels set vertically, not horizontally. Take a look at the illustrations below of incorrect and correct pier orientation, when the load-bearing piers are made of concrete masonry units (concrete blocks) with open or hollow channels.