An Alternative to Collar Ties in Roofing

Collar Ties and Ridge Beams

• Collar ties sometimes replace a ridge beam between the rafters from one end of the roof to another. In these cases, rafter tops are nailed together and collar ties are installed to hold the ends together. Installing a strong ridge board or beam with rafters fastened to it can eliminate the need for collar ties in some cases, especially in short roofs with light snow loads where there is not a great deal of downward thrust.

Vertical Braces

• Another alternative to collar ties are vertical supports under the rafters between the peak and wall, fastened to a horizontal joist connecting the walls. These braces, called webs, divert the downward thrust force from the wall connection to the joist. One or more braces may be required, depending on the rafter run or distance between the peak and the wall.

King Posts

• Installing “king” posts under ridge boards at each end of the roof will help support those beams, as an alternative to collar ties. The posts connect the bottom of the ridge board to the end wall caps and strengthen it against downward thrust. Adding additional vertical supports to the end rafters on each side of a king post will further strengthen the roof framing. Some roofs put king posts under each rafter peak.

Truss Techniques

• Using truss techniques also can eliminate the need for collar ties. Trusses are based on triangles, the strongest geometric form, and use diagonal braces between rafters and horizontal bottom chords. All trusses have bottom chords, which replace roof joists, top rafter chords and bracing webs between. The most common truss styles use webs angled between top and bottom chords in either a W- or K-pattern, with no horizontal ties.