ASHI created an Auxiliary Standard of Professional Practice for Residential Deck Inspections (ASPPRDI). Its purpose is to provide a more thorough and detailed inspection of residential wood deck components than what is done during a typical home inspection. The objective of the wood deck inspection is to determine if the deck components substantially conform to a deck construction guideline selected by the inspector. If they do not conform the inspector notes it in the report. The choices for deck construction guidelines are Design for Code Acceptance (DCA)-6, the International Residential Code (IRC) 2018 edition, and any local jurisdictional guidelines. Note that the deck may be approved by the local jurisdiction and not conform to either DCA-6 or IRC-18. DCA-6 was introduced by the American Wood Council (AWC) in 2007 and updated periodically. IRC was introduced in 1994 by the International Code Council (ICC) and updated periodically. The guidelines provide narratives, figures and tables that are definitive. Does the installation conform? Yes or no, the guidelines make it objective. There are limitations. Nearly all of the fasteners are embedded in the deck materials beyond visual sight. The ledger may be obstructed. Lattice may be installed making any components behind it not observable. Use best judgment and disclaim the obstructed components. Wood deck failures cause more injuries and death on residential properties than any other
cause. Search “deck failures” and click on images. What comes up boggles the mind. Many failures occur where the wood deck attaches to the house. This attachment is called the ledger and poor installation techniques leads to failure. Wood decks must resist vertical and lateral loads. It is the absence of lateral load connectors that contributes to ledger failures. Retrofitting lateral load connectors is nearly impossible. Wood stair failures are the number two cause of injuries and death on residential properties. Again, it is the attachment between the stairs and the deck.The wood deck has components of flashing and sealants, ledger board, flooring, posts, columns, footings, beams, guards, bracing, stairs, lighting, glazing and fasteners. Who knew there were so many components to look at? Here in southern Michigan, wood deck and stair footings go below the frost line which is 42”. Footings here are usually not visible. There should be lighting for the wood stairs, but none addressed for the wood deck. Some deck conditions make an ASPPIRDC ineligible. If a deck has a roof, a concentrated load (hot tub, etc.), has deck materials other than wood, or has multiple levels cannot fit into the guidelines.
A house I bought had the worst deck conditions I have seen. There were no ledger bolts, joist hangers, or approved fasteners present. The deck boards were warped and fastened with nails, the floor joists were fastened with ledger strips, and the deck guard was a single horizontal 2×10 @ 24” high. The stairs had no riser boards or handrails, or no acceptable guards. All of these conditions are safety hazards. I replaced the deck and it conforms to the current residential deck guidelines.