This can be from two causes.
How to extend gable end roof overhang.
For gabled roofs the roof rafters extending beyond the wall caps creating an angled roof overhang on the eaves.
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Inadequate nailing of the sheathing to supporting framing or inadequate connections of the framing at the rake edge that supports the roof.
How to extend gable end roof overhang.
Due to the steeper angle of gable roof the maximum width of the eaves is narrower than other shed styles.
For the arrangement of the gable end overhang for the standard roof you lengthen the ridge beam beyond the facade for previously verified length using cut rafters.
Extended roof overhang to match existing house.
Uplift of roof decking at the overhang the other common wind related failure at gable ends is uplift of the roof decking at the overhang.
However for larger extensions you ll need to hire a professional to get up there and remove large portions of the roof before extending the overhang.
Extending a gable roof can be tricky since it involves working on the roof but you may be able to do it yourself if you only need to add 1 2 2 inches 1 3 5 1 cm.