What should I use to overlay a particle board subfloor in my mobile home?
If you do in fact have only the 3/4" particle board now, you should not consider it structural. Therefore, I'd use 3/4" (23/32) tongue-and-groove OSB, which is standard as a basic single-layer subfloor in new homes. In areas where you want to install vinyl or other flooring requiring a prepared surface, use 3/4" t&amp;g BC plywood to avoid the need for additional underlayment.

If you actually have MDF (or some other high-performance pressed-particle product), which has more structural integrity, I'd consider a 1/2" or 5/8" BC, with the joints staggered from those of the MDF. You won't save a ton over the OSB (it may actually cost more), but it'll result in less of a height difference and has a nicer finished surface.