I recently inspected a home where the builder used single plates…this method of framing has been around for a long time however certain criteria is required for it to be approved. The main problem you have is the joints not being properly fastened with approved plating and/or the number of fasteners required per plating.
Every home I have inspected in Mecklenburg County that utilizes this type of framing the building inspectors have failed to find improper or missing ties/plates. I recently wrote one up where I went back 3 times and every time the building inspector and builder kept missing single wall plates that were not properly joined.
Currently the homeowner is actively engaged in suing the builder over this and many other issues the builder and building officials failed to address. An engineer was called in and he too found the same issues plus improper truss repairs as well as designs.
The other issue that you some times find, which is often outside of the building codes, is the 24 inch spacing often used for single plate framing; depending on the exterior veneer used the panels will often warp which translates to the exterior veneer…especially with stucco…this often is deemed cosmetic however homeowners do not view it the same way…and rightly so.
When such framing is utilized it is best to use a minimum of 5/8 - 3/4 inch sheathing
to prevent same; also blocking is required at all edges of the exterior panels in order to meet the fastening requirements at the edges of the sheathing.
Hope this helps…