hi tom
we've covered this many times in lots of threads...
here are just a few links to start from...
http://www.airforums.com/forums/f36/...-it-33396.html
http://www.airforums.com/forums/f365...bed-20767.html
http://www.airforums.com/forums/f349...rse-39275.html
working BACKWARD from RIGHT NOW...
the 16s and the 22s (discontinued) from this last decade have OSB subflooring.
and ALMOST all of the other recent units are plywood (not sure about the sports or 19s up to '04...)
the explanation on 16s is that a single sheet of osb can be used, and that wood sealant is used at the perimeter.
the 22s, especially the ones produced WITHOUT a complete belly wrap should be avoided.
before '98 flooring material is going to be alot more variable,
with osb apparently used in even the longest trailers in the early 90s.
i doubt that anyone can provide the absolute reliable guide to subfloors by year and model...
there doesn't appear to be one grand scheme prior to 98 dating back to 1935...
with so many 80s and 70s n older units repaired, patched or completely replaced, only adds to the variations.
every used trailer should be checked for signs of water damage, leaks and soft spots...
years of dripping from just one pipe joint under a sink or near the toilet will do great damage in one spot, but not a full floor.
while 20 year of a poorly sealed door or window roof leak draining behind a sofa is another issue entirely...
then there are flood damaged units, that may be much newer, but in very bad shape at the subfloor...
cheers
2air'