CSLB General Building (B)Framing and CarpentryMedium
A contractor is adding temporary let-in diagonal corner bracing to a wood-framed wall before sheathing is installed. For the brace to effectively resist racking, at what approximate angle should it be installed relative to the horizontal top and bottom plates?
- ABetween 10 and 20 degrees
- BBetween 70 and 80 degrees
- CBetween 45 and 60 degrees
- DExactly 90 degrees
Show answer & explanationAnswer & explanation
Correct answer: C. Between 45 and 60 degrees
Diagonal let-in braces are most effective at resisting racking forces when installed at an angle of roughly 45 to 60 degrees from horizontal. This angle range provides an efficient balance between vertical and horizontal force components, maximizing resistance to lateral (racking) movement of the wall.
Why the other options are wrong
- A. Too shallow; provides little resistance to vertical racking forces.
- B. Too steep; reduces horizontal component needed to resist racking.
- D. A vertical brace provides no diagonal triangulation to resist racking.
Let-In Diagonal Bracing
A temporary or permanent diagonal wood brace notched (let in) into studs to resist racking forces before or in place of structural sheathing.
- Effective angle range: 45-60 degrees from horizontal
- Provides temporary lateral stability during framing
- Often replaced by structural sheathing as the primary shear resistance
Memory trick: 'Halfway up, halfway strong — 45 to 60 does it long.'