Collar Ties vs. Rafter Ties
by Nick Gromicko and Kenton Shepard
Collar ties and rafter ties are both horizontal roof-framing members, each with different purposes and requirements.
Collar ties are designed to tie together the tops of opposing rafters. This helps brace the roof framing against uplift caused by wind. Collar ties must be placed in the upper third of the roof.
Other facts about collar ties:
- They may or may not be required, depending on jurisdiction. InterNACHI inspectors should not call out lack of collar ties as a defect unless they know that collar ties were required in the jurisdiction in which the home is located at the time the home was built.
- Collar ties are probably not needed if metal connectors were used to fasten the rafters to the ridge.
- Where they are required, they should be installed on every other rafter where rafters are on 24-inch centers.
- The 2006 International Residential Code (IRC) requires they have a minimum nominal dimension of 1-inch x 4-inch.
- Collar ties, contrary to popular belief, do not prevent walls from spreading.
Other facts about rafter ties:
- Rafter ties are always required unless the roof has a structural (self-supporting) ridge, or is built using engineered trusses. A lack of rafter ties is a serious structural issue in a conventionally framed roof.
- In most homes, the ceiling joists also serve as the rafter ties.
- Where rafters are oriented perpendicular to the ceiling joists, rafter ties should be installed just above the ceiling joists. The ties usually rest on the joists.
- When rafters are installed on 24-inch centers, rafter ties are typically installed every other rafter.
- Itís not unusual to see rafter ties of either 2-inch by 4-inch or 2-inch by 6-inch. The 2006 IRC requires them to be at least 2-inch by 4-inch.