Inspecting Single Ply Beams

Inspecting Single Ply Beams

Although a visual home inspection is not a code or engineering inspection, many home inspectors would require that beams and wood support members are multi-ply or built up beams. Commonly 2 – 2 by’s and a ½” piece of plywood sandwiched in the middle. Single ply beams would not be appropriate for door and window headers, or for spans supporting a second story or roof structure. Currently single ply beams are only acceptable for decks, porches and landings where no additional support is required. In the 2018 IRC, there is now a span table specifically for decks (Deck Beam Span Length’s for Single Ply Beams), the table is above. The table specifically addresses 2x6 – 2x12 single ply beams for deck joist spans. Using the table we can see a single ply 4’ 11” 2x6 can support spans up to 6’. A single ply 5’1”  2x8 can support spans of up to 8’. So what should a home inspector look for:

·         These spans also apply to stair landings not supporting a second floor or roof structure

·         This table applies to decks / porches and landings not supporting a second story

·         Roof structures that are being supported by a deck will require a larger beam / support member

·         Single ply beams are used for small spans

·         It is acceptable to use a single-ply beam in place of multi-ply beams as long as the size is appropriate

·         Single ply beams can be used for space requirements are an issue

·         Single ply beams will also save money