Issue Description:
Type IIIA construction is required to provide 2HR exterior wall assemblies for bearing walls. This requires an additional layer of 5/8″ Type X gypsum sheathing on the interior face of the wall. We have historically proposed framing modifications to our roof trusses to ensure that a girder truss is positioned close to the exterior wall so that the load is minimized to ensure non-bearing wall criteria is achieved. An example of this framing configuration can be seen below (R522 is one example). You can see the girders in RED.
While the above configuration does indeed reduce the simple gravity load on the exterior wall to meet the requirements making it non-bearing (less than 100lbs per lineal foot in addition to its own weight), it does not sufficiently decrease the total design gravity load, which incorporates additional factors such as wind. As an example, here is an excerpt from the same project, showing the loading information for one of the above jack trusses, R176:
You can see from the above that the load on the exterior wall, Point 5, has a gravity load of 1277. Diving by two (trusses are 24″ on center), and you can see that we well exceed the limits of the non-bearing wall definition.
All this to say, this configuration woud still require the exterior walls to be 2HR rated.
Proposed Resolution:
There are at least two options here.
1.) Frame the exterior wall in accordance with the detail below, ensuring that it is either balloon or semi-balloon framed for the top level portion to ensure that no additional loads are placed on the exterior wall.
2.) Provide 2HR wall ratings for the exterior walls and provide a simple framing layout that has the roof trusses bear on the exterior wall.
Framing Detail:
Commentary:
N/A
Additional Considerations:
. N/A