Roof Without Rafter Ties

In most homes the ceiling joists also serve as the rafter ties.

Roof without rafter ties.

The most common reason for installing collar ties is to prevent rafters from spreading apart under load. However in a conventionally framed peaked roof like the kind you describe collar ties would probably serve little or no function since the attic floor joists serve as ties to prevent the rafters from spreading. You can possibly remove them altogether of you include posts in the gable walls to support a structural ridge. Where rafters are oriented perpendicular to the ceiling joists rafter ties should be installed just above the ceiling joists.

From a practical perspective it s difficult to use high rafter ties on a low pitched roof because the force in each tie increases with the inverse of the pitch. Also see our blog post what causes a sagging roof ridge line. Like rafter ties collar ties are horizontal members that tie the rafters. Manufactured roof trusses do not need a ridge rafter or ridge beam.

A lack of rafter ties is a serious structural issue in a conventionally framed roof. If you are framing a cathedral ceiling there are a couple ways to deal with the need for rafter ties. But the spacing of the ties is reduced to 48 in. The bolts shown are not typically the way a conventional residential roof would be framed.

An engineer can design a roof with rafter ties on wider spacings look at the ridge and or wall plate as a beam if doing that. C so you can easily cover the underside of the roof with drywall and its outside with plywood. Collar ties collar ties are an alternative to rafter ties in framing where a conventional ceiling is not desirable. The prescriptive provisions of the building code require rafter ties on each rafter pair and collar ties every 4.

Rafter ties or ceiling joists acting as rafter ties are required by code unless the house is designed so that the walls or a structural ridge beam carries the full load of the roof. C and the flat ceiling is eliminated. You still have rafters 16 in. Without the proper support of rafter ties or a structural ridge a typical gable or sloped roof will sag downwards while pushing the building walls outwards towards a catastrophe such as that shown in our page top photo of a barn in amenia ny.

The failure of rafter ties in this building combined with snow loading in amenia new york pushed the ridge down and the walls outwards as the building slowly settles down to the earth. The ties usually rest on the joists.