hayeska
Structural
- Dec 28, 2003
- 46
T325 Roof Sheathing Fastening Schedules for Wind Uplift (Published by APA) Table 1
has the following footnote:
"When wind speed is 100 mph or greater, block panel edges perpendicular to gable-end-wall framing members in the first two bays of framing. Blocking shall be spaced a maximum of 4 feet o.c. (Wood Frame Construction Manual, Section 3.5.5)"
Question 1: Is the intent to secure the panel edges with respect to increased uplift or is it to increase the shear capacity in an otherwise unblocked diaphragm?
State code (amendment) allows for elimination of this blocking when using 5/8" T&G sheathing.
Therefore one would assume that it would be for uplift since the T&G would not transfer shear; would reduce potential for buckling at shear failure though.
I have also seen a variation of the of the amendment that calls for maintaining the blocking at the ridge and soffit(Zone 3 highest pressure), but eliminating it in between.
I have a detail that will transfer roof shear to the bearing wall while maintaining ventilation.
My problem would be at the ridge since 2x blocking on the flat would block the 1" air space; vaulted ceiling 2X12, 10-1/4" insulation, drywall attached to 2X12 rafters creating a confined space.
has the following footnote:
"When wind speed is 100 mph or greater, block panel edges perpendicular to gable-end-wall framing members in the first two bays of framing. Blocking shall be spaced a maximum of 4 feet o.c. (Wood Frame Construction Manual, Section 3.5.5)"
Question 1: Is the intent to secure the panel edges with respect to increased uplift or is it to increase the shear capacity in an otherwise unblocked diaphragm?
State code (amendment) allows for elimination of this blocking when using 5/8" T&G sheathing.
Therefore one would assume that it would be for uplift since the T&G would not transfer shear; would reduce potential for buckling at shear failure though.
I have also seen a variation of the of the amendment that calls for maintaining the blocking at the ridge and soffit(Zone 3 highest pressure), but eliminating it in between.
I have a detail that will transfer roof shear to the bearing wall while maintaining ventilation.
My problem would be at the ridge since 2x blocking on the flat would block the 1" air space; vaulted ceiling 2X12, 10-1/4" insulation, drywall attached to 2X12 rafters creating a confined space.
