To optimize headroom, the engineer allowed the crew to cut a slight taper on the underside of the sisters from the point where the rafter ties intersect to the end near the wall plates.

On a recent job, we were called in to repair a garage that had been converted to the primary bedroom of a home near Chicago. It was visually apparent that the roof had some deficiencies. The ridge had a substantial sag, which in turn pushed the exterior wall out of plumb upward of 3 1/2 inches at its worst location.

The roof structure was insulated and had been finished with wood paneling. It also included widely spaced tie beams that were more cosmetic than structural. Cathedral ceiling areas like this one require a structural ridge beam to support the roof loads, or adequate rafter ties or ceiling joists to resist the outward thrust of the roof loads. This building lacked both.

A true ridge beam should not be confused with a ridge board, which is not a structural member and functions only to make installing rafters easier during construction. A true ridge beam must be sized appropriately to support the roof loads and have a clear load path that transfers the loads through columns to a solid foundation. On top of a poorly designed ridge and inadequate ties, the roof rafters on this building were only 2x4s, which are greatly undersized for this part of the country.

Our job was to bring this home’s primary bedroom to a structurally sound state.

Read More