CSLB General Building (B)Framing and CarpentryMedium
A framer installs rafter ties across a roof to resist the outward thrust created by the rafters pushing on the exterior walls. According to standard framing practice, where should rafter ties generally be located along the rafter height for maximum effectiveness?
- AAs close to the ridge as possible
- BIn the lower third of the attic space, near the top plate
- CLocation does not matter as long as ties are installed somewhere
- DAt the exact midpoint of the rafter height
Show answer & explanationAnswer & explanation
Correct answer: B. In the lower third of the attic space, near the top plate
Rafter ties work most effectively when placed low, in the lower third of the attic space near the top plate, because they act like the bottom chord of a triangle, converting outward thrust into tension close to the wall's bearing point. Placing them near the ridge greatly reduces their effectiveness at resisting spread.
Why the other options are wrong
- A. Near the ridge, ties provide little resistance to outward wall thrust.
- C. Location is critical to the tie's structural function.
- D. A midpoint location is less effective than a lower placement.
Rafter Tie Placement
Rafter ties resist outward thrust from sloped rafters and are most effective when placed in the lower third of the attic near the top plate.
- Acts as tension member resisting rafter spread
- Best placed low, near wall top plate
- Ceiling joists often serve this function when aligned with rafters
Memory trick: Low ties tie down the thrust.