The way it was explained to me by my agent is, when the trailer is connected to my tow vehicle it's included in the vehicle's policy with the same coverage/limitations. When disconnected it's covered by homeowners insurance. I would think you could add a rider to your existing policy to cover it. I have no riders on either of mine. I think some collector car policies will allow trailer coverage.

It's been a while since I spoke with the insurance co.. I believe the trailer is covered when connected to the tow vehicle . If not connected and on my property my homeowners covers it. However when traveling and the trailer is disconnected it is not covered by either. My concern was coverage for vandalism or theft so I have a separate policy just for the trailer. It's only $20.00  an year and the deductible is $100.00 where my auto policy has a $1000.00 deductible. I know I can't replace the trailer for $800.00 and perhaps should get an appraisal from a dealer so I could increase the insured value as my policy is a "stated value " policy and due to the trailers age the insurance co. has limited its value to $800.00.