Bill, I don't know that there are any exact standards set out for the construction of a conversion shell. The RVIA (Recreational Vehicle Industry Association) does provide "codes" as in the commercial/residential building industry that governs construction, electrical, plumbing, etc,... from which most manufacturers adhere.
I visited several manufacturers in Elkhart Indiana, and one in Eastman Georgia, and got "somewhat" educated in how their conversions were built.
All (that were using steel tubing) used 16" centers in their wall construction. This makes sense as most demnensional building materials lend themselves to (even) division by 16". However, the floors & ceiling structure on some units used 2 foot spacing. This probably depends on the demensions of the steel being used.
Again, the conversion manufacturers that I observed, used 2"X 3" 11 guage for floor X-members (on 2 foot centers) and 2"X 2" sq tubing for ceilings (also on 2' centers).
You can learn a lot by touring some of the (Elkhart) production-line guys, especially Trendsetter & Showhauler.
When you draw out your floor plan just remember, you are working in sq inches, not sq feet and you need to make good use of every inch.
|