I am trying to add floor joists to an attic and intend for getting decent amount of support for plywood flooring and storage.
The existing truss is 13' across and 24'' span between 2x4 ceiling joists. these won't hold a pillowcase from what I've been told, even with the added support boards binding them to the rafters.
My question is what I can do about adding the support to joists so that I don't accidentally overload the wall itself. This garage wall is open but filled with cabinetry and would be a pain to add in extra studs. Do these added joists need to be above the studs period? If I don't sister the existing ceiling joists, will that be a mistake? I'm aware that the joists need to lay on the load baring walls but I'm not entirely certain how intense the requirements are for a bare plywood floor for storage space are.