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The key to keeping the top of the gable end wall braced against hurricane winds is to keep the roof sheathing in place. If you re-roof and follow the guidance for re-nailing the roof sheathing described in this guide, you will have done a lot to take care of this potential weakness. The exception would be if your roof overhang has outriggers since they need to be strapped down.

Sketch of Gable End Overhang Constructed Using Ladder Detail. The figure also indicates the directions of the wind forces that will tend to lift off the roof sheathing and gable overhang. (click image for larger version) Sketch of Gable End Overhang Constructed Using Outrigger Detail. – a conventionally framed gable end wall is shown but the situation would be nearly the same for a truss gable end wall. (click image for larger version)

Of the many ways that gable end overhangs are built the two most common ways are discussed here. One is to continue the truss size or rafter size all the way through the gable end and frame the gable overhang using what is commonly referred to as a ladder detail. In this system, the outer framing under the overhanging roof deck sheathing is formed by two long parallel 2x4’s or 2x6’s that are connected together laterally by short blocks, like the rungs of a ladder. It can be thought of as a rafter outside the attic and another one along the edge of the roof sheathing overhang. This framing is nailed to the outside face of the top chord of the last truss or rafter. The roof sheathing extends to the edge of the overhang and provides most of the support and resistance to uplift for the overhang. The second method uses outriggers and is more frequently used if the overhang is greater than 12”. In this system, the last truss or rafter is often made smaller than the rest so that the top chord of the truss or the rafter is 3.5” or 5.5” lower than the tops of the other trusses or rafters. Outriggers (2x4 or 2x6 members) are then installed on top of the gable truss or rafter so that they butt up against the truss or rafter next to the gable one, and extend out to support a fascia board along the edge of the overhang. They cantilever over the wall. If they cantilever over a gable end truss wall, sometimes the outriggers and trusses will have been (unfortunately) notched to allow installation of the outriggers when the gable truss is the same size as the other trusses. Frequently, these outriggers are only toe nailed to the inside rafter or truss and to the top of the gable end truss or rafter. Consequently, the connections of the outriggers themselves need to be checked and improved if needed. At the interior end you want to anchor the ends of the outriggers to the truss or rafter. Two or three 12d nails, nailed through the rafter or truss and into the end of the outrigger will hold the end in place. At the gable, you need to tie the outriggers down so that they don’t lift up. Adding a hurricane clip or tie such as a Simpson H2.5A or a USP RT7A between the outrigger and the gable end rafter or the top chord of the gable end truss is an easy and very effective way to help hold down the outriggers. If the outrigger has been notched, then using a tie at the notch may actually weaken the wood. For notched outriggers, a liberal use of construction adhesive along the top edges of the framing members so that they are glued to the roof sheathing and in the joints between the notches will strengthen the connections without damaging the wood. There are many different framing situations for outriggers. Consequently, you may have to modify what has been suggested; but, something that stabilizes the interior end of the outrigger and holds down the outrigger where it crosses the gable end is what you are trying to accomplish. For practically all gable end overhang situations using construction adhesive at every accessible joint between roof sheathing and any framing member is advisable.

If sheathing has not been re-nailed, use wood blocking with adhesive to make a strong connection between the sheathing and the rafter or truss at the gable and rafter or truss (click image for larger version) On the next two rafters or trusses in from the gable end, apply a 1/4-inch bead of adhesive along each side of the rafter or truss. (click image for larger version)

If you are not ready to re-roof or have just re-roofed and did not get the deck re-nailed, you may still be able to reduce this vulnerability by using the sub-floor adhesive technique to retrofit the roof deck attachment that is described in Enhancing Roof Sheathing Attachment Strength. Since you will only be able to get at one side of the gable end truss or rafter, we recommend using wood blocking, with adhesive on two adjacent sides, to glue the roof sheathing to the last gable truss or rafter. In addition, we recommend that you apply Ό-inch beads of adhesive to both sides of the two rafters or trusses that are next to the gable end truss or rafter and any other joints between the sheathing and the framing, regardless of the direction of the framing, within 4’ of the gable end. Applying construction adhesive between roof sheathing and all framing members within 4’ of the gable end is advisable. Gable end overhangs are a great place for wind to both push up on the overhang and lift from the top as the wind speeds up over the top of the roof. By applying adhesive from within the attic in this area, you are helping to hold down sheathing over the living area, even if it begins to tear loose at the overhang. The outriggers themselves (2x4’s or 2x6’s) need to be well secured at the end furthest into the attic and where they rest on the gable end wall. In homes that have not been built to modern high wind standards, there may only be a few toe nails holding these outriggers in place.

The roof sheathing by itself may not be able to hold the full force of the wind on the gable wall without buckling of the sheathing. Consequently, most gable end bracing designs, including the one provided in this guide, require that blocking (wood members attached between the rafters or trusses and running perpendicular to the rafters and trusses) be added. The gable end bracing retrofit guide can be viewed on-line or download a PDF Version .

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