TimberStrand庐 laminated strand lumber (LSL) is an engineered lumber that is consistently straight and true 鈥� characteristics that combine to create superior rim board material. TimberStrand Rim Board is dimensionally stable and excels at transferring vertical and lateral loads to the foundation. Sized to fit with TJI庐 joists, TimberStrand Rim Board is designed to provide critical performance where you need it most.