Guide · Drawings · 13 min read
Reading a Structural Drawing: A Homeowner's Field Guide
A residential structural drawing set is organized into general notes, foundation plans, framing plans, details and schedules, backed by calculations. Each member is identified by a callout giving its size and material; symbols point to details and sections on other sheets. Knowing a dozen symbols and abbreviations is enough to follow what will be built in your house.
Reviewed by Daniel R. Whitcomb, PE · WA PE 48217
How is a structural drawing set organized?
Structural sheets are usually numbered with an S prefix, and they follow a predictable order. On a small project several of these may be combined onto one or two sheets.
| Sheet | Contents |
|---|---|
| S0 or S1 · General notes | Codes, design loads, material grades, inspection requirements |
| Foundation plan | Footings, stem walls, piers, anchor bolts, hold-down locations |
| Floor framing plan | Joists, beams, posts and their direction and spacing |
| Roof framing plan | Rafters or trusses, ridge, hips, valleys, beams |
| Shear wall plan | Which walls resist lateral loads and how they are built |
| Details and sections | Enlarged views of connections, bearings and edges |
| Calculations (separate package) | The engineering math behind every member, stamped |
What does the title block tell you?
Every sheet has a title block, usually along the right edge or bottom. It shows the project address, sheet number and title, the date and revision history, the drafter and the engineer of record. The engineer's stamp and signature certify that the structural design was prepared under their responsible charge and is licensed in Washington. Check the revision box: plans change during permit review, and the crew must build from the latest approved revision, which carries the city's approval stamp.
How do you read a framing plan?
A framing plan is a view looking straight down at one level of the structure, with the ceiling or floor framing drawn as if you could see through the finishes. The drawing below is a simplified excerpt of the kind of plan used for a wall removal.
Read it in this order: find the north arrow and the overall outline; identify which way the joists run, shown by thin parallel lines with an arrow and a callout such as "2x8 CJ @ 16 in O.C." (ceiling joists at 16 inches on center); find the beams, usually drawn as heavier lines with a mark like B1; locate the posts at beam ends; then follow the bubbles to the details that show how each piece connects.
What do the lines and symbols mean?
| Symbol | Meaning |
|---|---|
| Solid heavy line | A wall or beam being cut through or at the level shown |
| Dashed line | Something hidden or above or below the plane: a footing under a slab, a beam above |
| Long-short dashed line | A center line or grid line |
| Line with an arrow and spacing note | Joists or rafters running in the arrow's direction at the stated spacing |
| Circle split by a line (bubble) | Detail callout: top number is the detail, bottom is the sheet where it appears |
| Line with arrows or flags at both ends and a letter | Section cut: look for the section with that letter on another sheet |
| Filled square or rectangle | A post or column |
| Hatched band along a wall | A shear wall, with a tag pointing to the shear wall schedule |
| Triangle or hexagon with a mark | A hold-down or revision marker, depending on the legend |
Every set has a legend, usually on the first sheet; when a symbol looks unfamiliar, the legend is the authority.
How do you read a member callout?
A callout tells you what a member is made of, its size and sometimes how many pieces make it up.
- "(3) 1-3/4 x 14 LVL" means three plies of laminated veneer lumber, each 1-3/4 inches thick and 14 inches deep, fastened together.
- "5-1/8 x 12 GLB" is a glulam beam 5-1/8 inches wide and 12 inches deep.
- "W8x18" is a steel wide-flange beam about 8 inches deep weighing 18 pounds per foot.
- "4x10 DF #2 HDR" is a header made from a 4x10 of Douglas fir-larch, grade No. 2.
- "6x6 POST" or "(3) 2x6 POST" describes a solid or built-up post.
- "FLUSH" or "DROPPED" says whether the beam sits in the joist depth or below it.
Nominal lumber sizes are larger than actual: a 2x8 is about 1-1/2 by 7-1/4 inches. Engineered lumber and steel are listed at actual dimensions.
What are schedules, and why do they matter?
To keep plans readable, repeated information is collected into tables called schedules, and the plan uses short tags that point to them.
| Schedule | Typical tag | What it lists |
|---|---|---|
| Beam schedule | B1, B2 | Size, material, bearing length, connections |
| Footing schedule | F1, F2 | Width, length, depth, reinforcement |
| Shear wall schedule | SW1, SW2 | Sheathing type and thickness, nail size and spacing at edges and field, sill anchors |
| Hold-down schedule | HD1, HD2 | Hardware type, anchor size and embedment, post size |
| Header schedule | H1, H2 | Header size by opening width and wall |
Shear wall nailing is the schedule item inspectors check most closely. A note such as "8d at 4 in o.c. edges, 12 in o.c. field" means nails at 4-inch spacing along every panel edge and 12-inch spacing in the middle; getting it wrong is a common reason for a failed framing inspection.
Which abbreviations appear most often?
| Abbreviation | Meaning |
|---|---|
| O.C. | On center: spacing measured center to center |
| TYP. | Typical: applies to all similar conditions |
| U.N.O. | Unless noted otherwise |
| CJ / FJ / RR | Ceiling joist / floor joist / roof rafter |
| DF-L | Douglas fir-larch lumber species group |
| LVL / PSL / GLB | Laminated veneer lumber / parallel strand lumber / glulam beam |
| HDR / BM / PT | Header / beam / pressure-treated |
| BRG | Bearing: where a member rests on its support |
| EQ. | Equal spacing |
| EOR | Engineer of record |
| T&B | Top and bottom |
What is in the general notes, and why read them?
General notes set rules for everything not drawn individually. They list the code edition the design follows, design loads for floors, roofs, wind and earthquakes, required grades of lumber and concrete strength, fastener types, and which inspections the engineer requires before work is covered. When a plan shows a member without a full callout, the general notes usually fill the gap with a "typical" requirement. For an owner, the notes are also where you find what the engineer expects to see on site before approval, which is useful when scheduling.
The code requirements referenced in the notes can be read in the ICC code library, with Washington amendments from the State Building Code Council.
Next steps with your drawing set in hand
Related questions
More about structural drawings
What is the difference between structural drawings and calculations?
Drawings show what to build: sizes, locations and connections. Calculations show why those sizes work: the loads, the analysis and the checks against code limits. Building departments review both. Crews build from the drawings; the calculations stay with the permit record and the engineer, and are referenced if questions arise later.
Can the contractor substitute a different beam than the one drawn?
Only with the engineer's written approval, and sometimes the city's. A substitute may look equivalent but differ in strength, stiffness or connection requirements. Engineers commonly approve substitutions such as a PSL for an LVL when they check the numbers. Unapproved substitutions are a frequent reason for failed inspections.
Why do my architectural and structural drawings show different things?
They show different information about the same building. Architectural sheets show layout, finishes and dimensions; structural sheets show the framing behind them. Where they appear to conflict, such as a post drawn where the architectural plan shows a doorway, the conflict needs to be resolved by the designer and engineer before construction, not on site.
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