TaxGuyBill
Level 15

Sorry, I hit the button too soon, I wasn't finished.

But it is not merely whether or not it is §1250 property or not.  Nonresidential Property is defined in §168 as:

The term “nonresidential real property” means section 1250 property which is not—

(ii)
property with a class life of less than 27.5 years.
 
 
So if it has a class life of less than 27.5 years, it would not be "Nonresidential Real Property".
 
You did call it a "trailer", which does have a class life of less than 27.5 years.  (See Revenue Procedure 87-56 and/or the listing in Publication 946).  Personally, I think the way you described the property it does not seem to be a "trailer" in the sense of those categories (seems to apply to the things that vehicles tow), but if you wanted to be aggressive, that would be your basis.
 
So I would still use 39 years and no Bonus, but if you think it really fits the category of a "trailer", you have that option.