When our 2-story garage was built in 2006, we didn't have plywood placed outside the joists, and then the Tyvek on the outside of plywood, then Hardy plank siding on the Tyvek. A friend who came by after the garage was built visibly noticed the Tyvek through the joists, and said you "have no support." Thus, I installed R19 insulation between the joists and then 1/2 plywood all the way around the first floor and 2nd floor on the inside -- using deck screws fastened into the joists every 16 inches. The thinking was that, later, if we want sheet rock, we could use 3/8" over the plywood. (for now, don't worry about electrical work, assuming the original electrical works doesn't change).
The garage measures 20' x 30' so the 2nd floor is a large area.
Our new contractor who is finishing the upstairs pulled the plywood off (only on the 2nd floor) because he stated that:
"plywood doesn't breath like sheet-rock, and with a large 10-30 degree temperature differential between the Tyvek/Hardy surface and the plywood during AC usage in summer and heating in the winter, the risk of condensation and hence mildew is very high. Therefore, we should just use 5/8" sheet-rock to act as the support."
Please note that in the attic, all of the weight of the center of the roof bears down on the center of the attic floor, based on vertical joists. There are no vertical joists at 1/4 and 3/4 the width of the attic to distribute the weight.
After removing the plywood that provided structure, we have noticed that some surfaces are not level on attic floor joists (beams).
So the contractor said today that all of the weight of the roof, which is only supported by center vertical joists, is causing the attic floor joists to rotate slightly resulting in bowing/sagging. He then said what really needs to be done is to build a temporary false wall running down the center of the first floor (90 degrees to the 2nd floor joists), and jack that up. Then, on the second floor, build another temporary wall 90 degrees to the attic floor joists, and then in the attic add vertical runner joists at the 1/4 and 3/4 attic-width locations in order to more evenly distribute the weight of the roof. Then, once that is done, nail in short alternating 2"x6" cross boards positioned like "X" between the attic floor joists -- essentially to prevent the joists from rolling and rotating -- which is what will allow them to bow. The cross-members once nailed in when the false walls are in place with everything level will provide tremendous support and minimize bowing of the entire structure.
While this sounds good, I do think a large reason why the garage is shifting is because the plywood I screwed in all the way around the 2nd floor was removed, and the weight of the roof is now coming down harder causing more bowing. Interestingly, if the contractor assumed that 5/8" sheet-rock could take the place of the plywood for support, I think the sheet-rock would eventually split open and the weight of the roof would eventually tear it all apart.
Do you recommend going the route of building false temporary walls on the first and second floors, jacking up the first to level out bowing upstairs and in the attic, and then fasten vertical joists to the roof joists at 1/4 and 3/4 attic-width locations, add alternating cross members to the attic floor joists (looking up from the second floor), and then use 5/8" sheet-rock on the interior walls on the second floor?
The garage measures 20' x 30' so the 2nd floor is a large area.
Our new contractor who is finishing the upstairs pulled the plywood off (only on the 2nd floor) because he stated that:
"plywood doesn't breath like sheet-rock, and with a large 10-30 degree temperature differential between the Tyvek/Hardy surface and the plywood during AC usage in summer and heating in the winter, the risk of condensation and hence mildew is very high. Therefore, we should just use 5/8" sheet-rock to act as the support."
Please note that in the attic, all of the weight of the center of the roof bears down on the center of the attic floor, based on vertical joists. There are no vertical joists at 1/4 and 3/4 the width of the attic to distribute the weight.
After removing the plywood that provided structure, we have noticed that some surfaces are not level on attic floor joists (beams).
So the contractor said today that all of the weight of the roof, which is only supported by center vertical joists, is causing the attic floor joists to rotate slightly resulting in bowing/sagging. He then said what really needs to be done is to build a temporary false wall running down the center of the first floor (90 degrees to the 2nd floor joists), and jack that up. Then, on the second floor, build another temporary wall 90 degrees to the attic floor joists, and then in the attic add vertical runner joists at the 1/4 and 3/4 attic-width locations in order to more evenly distribute the weight of the roof. Then, once that is done, nail in short alternating 2"x6" cross boards positioned like "X" between the attic floor joists -- essentially to prevent the joists from rolling and rotating -- which is what will allow them to bow. The cross-members once nailed in when the false walls are in place with everything level will provide tremendous support and minimize bowing of the entire structure.
While this sounds good, I do think a large reason why the garage is shifting is because the plywood I screwed in all the way around the 2nd floor was removed, and the weight of the roof is now coming down harder causing more bowing. Interestingly, if the contractor assumed that 5/8" sheet-rock could take the place of the plywood for support, I think the sheet-rock would eventually split open and the weight of the roof would eventually tear it all apart.
Do you recommend going the route of building false temporary walls on the first and second floors, jacking up the first to level out bowing upstairs and in the attic, and then fasten vertical joists to the roof joists at 1/4 and 3/4 attic-width locations, add alternating cross members to the attic floor joists (looking up from the second floor), and then use 5/8" sheet-rock on the interior walls on the second floor?
