Structural design basics: how to read architectural drawings

What architectural and structural drawings each communicate

Connor Conzelman opened the session using a drawing set for a residential project in Taos, New Mexico, provided by Calcs.com user Jason Michael Neil. The set covered a two-storey home on a sloped site and served as a practical example of a compact but complete construction document package.

Architectural drawings convey how the building looks and functions: room layouts, fixture locations, door and window schedules, and finish specifications. Structural drawings convey how the building stands: concrete walls, post and beam framing, shear elements, and connections. Both sets are needed to do structural design, but they serve different purposes. Architectural drawings define the geometry the structure must fit within; structural drawings define the members and connections that resist loads within that geometry.

The drawing set for the Taos project ran from sheet S0.1 to S3.4. Connor noted that knowing the sheet range from the sheet index, usually located on the general notes page, is the first step in navigating any drawing set.

Page nomenclature and the sheet index

Sheet numbers follow a consistent convention: a discipline letter, an optional second letter indicating the sheet type, a digit indicating the category, and a sequence number. S identifies structural sheets, A identifies architectural, and M identifies mechanical. Within the structural series, S0 sheets typically carry general notes and schedules, S1 sheets carry foundation plans, S2 sheets carry framing plans, and S3 sheets carry sections and details. This convention is not universal but is common enough that most drawing sets follow it approximately.

Connor showed the sheet index on the general notes page, which listed every sheet by number and title. Reading the index at the start of a review session is more efficient than scrolling through sheets searching for specific information.

General notes and design loads

The general notes for the Taos project specified IBC 2015 with New Mexico revisions as the governing code, a residential live load of 40 psf, and a dead load of 20 psf. Connor noted that the structural drawings are the authoritative reference for design loads used in calculations because they carry the engineer of record's stamp, while the architectural drawings may specify no structural loads at all.

He warned against copying general notes from a prior project without a full review. Notes contain permit-specific requirements and sometimes prohibit substitutions or cite code editions that do not apply to the current jurisdiction. An engineer who pastes notes from a California project onto a New Mexico project risks including California-specific requirements or material standards that conflict with the actual design basis.

For engineers who need to find a jurisdiction's adopted code before drawings are available, Connor recommended searching the county name and "building permit information" to reach the building department's published code adoption table, or calling the department directly.

Locating structural members using grid lines, schedules, and detail symbols

Grid lines run across every sheet in a drawing set, labeling column lines and reference points consistently so that the same grid intersection identifies the same physical location on the site plan, floor plan, and sections. Connor traced a ridge beam from the upper-level floor plan through the grid reference to a pair of 10x10 Douglas Fir posts shown on the same plan, then located those posts on the first-floor plan by matching grid coordinates. This floor-to-floor tracing is how an engineer confirms the vertical load path and identifies where reactions from upper members land on lower members.

Member schedules appear as a separate table, usually on the general notes or framing plan sheets, and use a symbol to tag each distinct member type. In the Taos project, a hexagonal symbol identified each member type: symbol 1 identified a 10x10 Douglas Fir No. 2 post. The schedule maps every tag on the floor plan to a specific material, grade, and size, and is one of the first tables to locate when setting up calculations.

Detail symbols appear as a circle divided horizontally. The upper number is the detail number and the lower number is the sheet where that detail appears. Connor demonstrated navigating from a deck framing callout on the floor plan to detail 7 on sheet S3.3, which showed 2x10 joists at 16 inches on center bearing on a 10x18 beam. Following the detail symbol closes the gap between the floor plan's simplified representation and the actual construction requirement.