How to Read a Wall Type Legend on Construction Drawings

The wall type legend is the most important sheet in a drywall or framing takeoff, and the easiest one to misread. It tells you what every wall on the floor plans is actually made of. Get it right and every quantity downstream is right; get one tag wrong and it's wrong on every sheet.

What a wall type legend is

Architects don't write out "2x4 wood studs at 16" o.c. with 5/8" gypsum board both sides" on every wall. They define each assembly once in a table (usually titled Wall Types or Partition Types), give it a short tag like A4, and put that tag on the floor plans. The legend is the key that turns tags into materials.

A real example

This is the wall type table from a real 21-page apartment renovation (Freeport Square Apartments), simplified:

Notice that A4 and C4 are the same thickness but different materials: C4 needs fire-rated Type X board. You can't tell them apart by measuring the wall; only the tag on the plan says which is which.

How to read each column

• Tag / sub-type: the label you'll find on the floor plans (often in a diamond or hexagon). A letter usually means the family (A = partitions, B = furring, C = rated), the number the stud size.
• Stud width: the framing member alone: 3 1/2" (2x4), 5 1/2" (2x6), 3 5/8" or 6" steel.
• Assembly width: the finished wall, board included. This is what you'd measure on the drawing: a 2x4 with 5/8" board both sides is 3 1/2 + 5/8 + 5/8 = 4 3/4".
• Fire rating / UL design: rated walls usually mean Type X board, sometimes two layers, and continuous to the deck. Budget for it.
• STC: sound rating. Higher STC often adds insulation, a second layer or resilient channel, which all change your counts.
• Typical notes: read them. "Partition type A4 unless noted otherwise" means every untagged wall is A4.

Using the legend in a takeoff

1. Find the legend first, before measuring anything. It's often on an early A-sheet, or sharing a sheet with the door schedule.
2. List every tag with its stud size, board layers and sides, rating and height (to deck or to ceiling).
3. Measure linear feet of wall per tag on the floor plans.
4. Convert each tag's footage into studs, track or plates, board, and insulation. Our free metal stud, wood stud and drywall calculators do the per-wall math.
5. Flag walls with no tag and walls the legend doesn't cover (exterior walls are often detailed elsewhere). Those are where takeoff errors hide.

Common mistakes

• Same thickness, different assembly: a rated and a non-rated wall can be identical in plan. Always go by the tag.
• Missing the default note: untagged walls aren't "unknown"; the typical note usually defines them.
• Ignoring height: "to deck" vs. "6" above ceiling" can change board quantities by a third.
• Reading a scanned legend: blurry fractions (4 3/4 vs 4 1/4) are easy to misread; get the vector PDF.

How ReadMyBlueprint uses the legend

ReadMyBlueprint reads the wall type table straight from a digital PDF, measures every wall's real thickness from the drawing geometry, and matches each wall to its legend row. Walls that match are counted automatically; walls the legend doesn't cover, or two rows could explain, are flagged for a one-click confirmation instead of guessed. See how wall-type matching works, or the real test on the plan set above.

Quick answers

What is a wall type legend?

A table on the architectural drawings (often titled Wall Types or Partition Types) that defines every wall assembly used on the project and gives each one a tag, like A4 or C6. Floor plans then label each wall with its tag instead of repeating the full assembly.

What is the difference between stud width and assembly width?

Stud width is the framing member alone (3 1/2" for a 2x4, 3 5/8" for a common steel stud). Assembly width is the finished wall including every layer of board: a 2x4 with 5/8" gypsum on both sides is 4 3/4".

What does STC mean on a wall type?

Sound Transmission Class: how well the assembly blocks airborne sound. Higher is better; STC 50+ is typical between apartments. It often means extra layers, insulation or resilient channel, which change your material counts.

Where do I find the wall type legend?

Usually on an early architectural sheet (A0.x or G-series) or on the same sheet as the door schedule. Some sets put partition types on each floor plan; on others, notes like 'partition type A4 unless noted otherwise' set the default wall.

Related: How to do a construction takeoff · Glossary · Free calculators · Drywall takeoff

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