Framing Gable End Overhangs
Question:
What is the recommended way to frame gable end overhangs?
Answer:
Framing for gable end overhangs (rakes) for steel framing is codified in the IRC 2012/2015 R804. There are no similar requirements for wood framing. The American Wood Council’s 2012 Wood Frame Construction Manual defines rake overhang as “The horizontal projection of the roof measured from the outside face of the gable endwall to the outside edge of the roof.” Section 2.1.3.4.c states, “Rake overhangs shall not exceed the lesser of one-half the purlin length or 2 feet” and makes an exception for “Rake overhangs using lookout blocks[, which] shall not exceed 1 foot.”
Design of gable rake overhangs may also have an impact on the design of the framing of the gable below. In areas where snow is the primary concern, gravity loads must be considered. In areas where wind is the primary concern, design for uplift and bending must be considered.
Some a general rules for rake overhang framing are:
- Notching a gable frame top chord should not be used with structural gable ends, drag struts or partial bearing trusses. The only exceptions are trusses that have been analyzed and sealed by a truss engineer, and which can take the notched top chord into account.
- Tack-on ladders should only be used for overhangs up to 12 in.
- 2x4 ladders with one dropped gable truss are applicable for overhangs up to 2 ft.
- 2x6 ladders with one dropped gable truss and one dropped truss are applicable for overhangs up to 3 ft.
- Except for tack-on ladders, have the ladder framing extend into the roof a distance at least equal to the overhang.