BIDSIMP INTERACTIVE LESSON
Let's work through a wall together.
We'll go step by step from a finished architectural dimension to the bare-track layout dimension.
GUIDED LESSON
Ready to start?
Click Start a Guided Wall to begin.
Learning aid: This lesson uses one layer of 5/8" drywall on each wall face to teach the finish-to-track relationship. Actual wall types may include different drywall thicknesses, multiple layers, plywood, tile, millwork, wall panels, shaftwall components, or other finishes. Always verify the drawings, wall types, finish schedule, specifications, and field control before laying out framing. Terms & Disclaimer
GUIDED METAL FRAMING LAYOUT
Read the witness lines before changing the dimension.
Architectural dimensions often locate finished faces, while the layout crew must mark bare track. This guided lesson teaches the relationship without a timer. Every wall uses one layer of 5/8-inch drywall per face so the endpoint logic is easy to see before moving into mixed wall build-ups.
Follow each witness line to the exact finished face. The same written dimension can require a different track adjustment when its endpoints change.
Ask whether the highlighted track points are farther apart, closer together, or offset equally from the finished points.
Two affected faces total 1-1/4 inches. A fixed axis changes only at the wall endpoint, and mixed inside/outside effects can cancel.
The four decisions behind the guided wall
- Identify whether each architectural witness line lands on an inside finish, outside finish, or fixed axis.
- Locate the nearest bare-track edge that the crew must actually mark.
- Decide whether moving from finish to track makes the layout distance bigger, smaller, or unchanged.
- Add, subtract, or cancel the finish build-up and state the final bare-track layout dimension.
Inside-finish to inside-finish dimensions usually grow when converted to the nearest track edges. Outside-finish to outside-finish dimensions usually shrink. When one endpoint is inside and the other is outside with equal finish thicknesses, one adjustment increases the distance while the other decreases it, so the net change is zero.
WORKED EXAMPLE
10'-0" outside finish to outside finish
- The given dimension runs between two outside finished drywall faces.
- The nearest outside track edge is 5/8 inch inward from each finished face.
- 5/8 inch + 5/8 inch = 1-1/4 inches total.
- 10'-0" - 1-1/4" = 9'-10 3/4" between the highlighted outside track edges.
With the same wall build-up, an inside-finish to inside-finish dimension would increase by 1-1/4 inches instead.
Common mistakes
- Subtracting drywall automatically without reading which face is dimensioned.
- Adjusting both ends of an axis dimension even though the axis does not move.
- Using the full wall thickness when the target is only the nearest track edge.
- Assuming both wall faces have the same number or thickness of finish layers.
Verify before snapping track
- Wall-type details and finish schedules.
- Witness-line endpoints and controlling grid or axis lines.
- Drywall, plywood, tile, panel, or millwork build-ups at each face.
- Field control, existing conditions, tolerances, and approved coordination drawings.