Lower awning mount

[vcrt]

The first thing I would check is to see how far the flooring is rotted. Since the steel frame rail is located about a foot in from the siding, you are limited as to how much work you can do from below. You will have to drop the black Darco under covering to find out, but again, the frame rail is going to be in the way, so you'll probably have to be cutting it to pull it away. It can be patched back into place when you're done.
Can any of the storage compartment walls be removed from inside? You may have to get creative when it comes to pulling out wood panels that were screwed in from the outside at the factory. Then, once you've exposed the OSB wood flooring to the extent of the rot damage, you can lift the vinyl flooring so you can remove the rotted portions of OSB.
Any OSB that is rotted over and inboard of the frame rail will most likely have to come out from above.
Keep us posted, and BTW, since you'll be starting a project, it probably would be a good idea to start a new thread. It makes it easier to find by those who will be facing the same type of work in the future.
Rich

[j52wf]

I can hit solid floor inside the storage compartment. I took the compartment walls out already. Guess I'll pull down the darco today and start rippibg out wood. That is one if my concerns, fixing that membrane. I'm thinking Gorilla Tape?

[vcrt]

JohnB has done that, maybe he'll jump in here and give you the link to his post on it.
Glad to hear that the rot doesn't extend outside the storage compartment!
Rich