I have an apartment building with townhome style apartments. There is no fire separation wall between the units from the crawl space to the attic. Does anyone know how I could build a fire resistant separation wall between adjoining units which would allow me to subdivide the building as actual legal parcels and sell them as individual townhomes? Brick is not feasible but some sort of heavy sheetrock going through from the crawl to the the attic space and through the roofline may be doable.