Untreated wood in direct contact with the ground is susceptible to rot and termite infestation. In addition, the dampness normally associated with the soil can also promote rust deterioration of a metal post or connector.
Moreover, each post should rest on a concrete pad that has a footing below the frost line, otherwise the footing is vulnerable to frost heave. During the deck inspection, probe the base sections of the posts with a screwdriver or ice pick to check for deterioration. If the screwdriver penetrates the post beyond the surface, there is a problem that should be corrected. In some cases, the post may require replacement.
The post should not move, so push it to check if it does. If columns are loose, they are not properly supporting the deck. This condition is usually caused by uneven settlement of the support footings and inadequate fastening at the top or bottom of the column. A loose post should be re-secured as soon as possible because it is a potential safety hazard.
If the deck is less than a few feet above the ground, it will usually be supported by masonry piers. Examine the piers for cracked, broken, loose or deteriorated sections. If you find any, record the condition on your worksheet for future repair. In some cases, usually with decks less than a foot above the ground, this inspection may not be possible because most of the support piers are not visible.
If one side of the deck is attached to the house, usually there are no support posts below that section, so if the joint between the house and the deck weakens it would cause the deck to collapse. Examine the joint between the deck and the house to check if it is securely fastened. If it is pulling away from the house, record the condition on your worksheet for additional bracing.
Sometimes, the deck is fastened to the house with undersized or insufficient nails, a condition that could cause the deck to collapse. Because of this potential hazard, some communities require using lag bolts rather than nails to secure the deck to the house.
Finally, check the joist supports at the section of the deck attached to the house. Because there are no posts, there will not be a girder to support the joists. In this case, the joists should be supported with a ledger below them. A girder, however, would be preferable because the ledger used is often not enough. With many decks, the joists were toe-nailed into the header, but the ledger was never installed. If you come across this type of installation, install angle brackets to support the joists. Examine the condition of all metal brackets, connectors, nails and screws to check for corrosion and rust.