6.4 Structural Framing: Wood & Steel, Including Decks

Platform Framing: The Standard Wood-Framing Method

Platform framing (also called western framing) is the dominant method of wood-framed residential construction in the United States, including Massachusetts. In platform framing, each story of the building is framed as its own complete, self-contained platform: the floor framing for that story is built and sheathed first, creating a flat working platform, and the walls for that story are then framed (often built flat on the platform and tilted up) and raised on top of it. Once that story's walls are up, the process repeats -- the next floor platform is framed on top of those walls, and so on up to the roof.

This method is popular because each platform provides a safe, flat working surface for the crew framing the level above, and because it allows each story to be framed with dimensional lumber cut to manageable, story-height lengths rather than requiring lumber that spans the full height of the building.

Key Framing Members and Their Function

Headers: Transferring Load Around Openings

Every window and door opening in a load-bearing wall removes studs that would otherwise be carrying load straight down to the foundation. A header is the structural member placed above the opening to pick up that load and redirect it, through the framing on either side of the opening (often doubled studs, sometimes called jack studs or trimmers), back down to the foundation. Header sizing depends on the width of the opening being spanned and the load it must carry -- wider openings and heavier loads require larger or engineered headers. Recognizing that a header exists specifically to solve this exact problem (missing studs under load) is the core concept the exam is testing when it asks about headers, more than any specific dimension.

Load-Path Thinking: From Roof to Foundation

A useful mental model for nearly every structural question on this exam is the load path: the continuous route a load takes from where it originates (typically the roof, receiving snow and its own weight) down through the structure to the ground. In a conventionally framed house, that path generally runs roof, to rafters or trusses, to exterior/load-bearing walls, to the sill plate, to the foundation, to the soil. Every connection along that path (rafter-to-wall, wall-to-sill, sill-to-foundation) has to be capable of transferring the load to the next link. A broken load path -- for example, a load-bearing wall removed without a properly sized header and adequate support beneath it -- is a serious structural hazard, even if nothing looks visibly wrong at first. When evaluating a scenario question, trace the load path from its origin to the foundation and check whether every link is accounted for.

Steel Framing as an Alternative

Steel framing (typically cold-formed, light-gauge steel members) is used as an alternative to wood in some Massachusetts construction, both commercial and, less commonly, residential. As a general matter of material properties (see Section 6.1), steel framing is noncombustible, which changes its role in fire-resistance-rated assemblies compared to wood framing, and it does not shrink, warp, or attract wood-boring insects the way lumber can. Structurally, steel framing behaves differently than wood in terms of connections (steel framing members are typically screwed rather than nailed) and can be engineered for different span capabilities. The exam expects you to recognize steel framing as a distinct system with its own general characteristics, not to treat it as a drop-in substitute governed by identical rules to wood framing.

Decks: The Highest-Scrutiny Residential Structure

Deck construction receives disproportionate code attention relative to its size, because deck failures, often sudden and with people standing on the structure at the time, have caused serious injuries and fatalities nationally. Three fundamentals govern safe deck construction:

• Ledger board attachment: A deck's ledger board is the horizontal member bolted to the house's structural framing (the band joist or rim board) to support one side of the deck. Improper or inadequate ledger attachment -- using nails instead of proper structural fasteners, attaching only to siding or sheathing rather than to the house's actual framing, or failing to flash the connection against water intrusion -- is widely recognized as one of the leading causes of deck collapse. Flashing at the ledger connection matters because trapped moisture rots the framing behind the ledger over time, silently weakening a connection that may have been installed correctly.
• Footing depth: Like any other foundation element discussed in Section 6.2, deck footings must extend below the local frost depth to prevent frost heave from lifting or shifting the deck's support posts over time.
• Joist and beam sizing: Deck joists and beams must be sized appropriately for the span they cover and the load (the dead load of the structure plus the live load of occupants and furnishings) they must carry -- undersized framing is a hazard even when every connection is otherwise correct.

Treat decks as a full structural system, not an easy add-on. The combination of live load concentration (people gathering on a relatively small platform), outdoor exposure, and a single critical connection point at the ledger is exactly why this area draws heavy code scrutiny.