The floor in the dinette is separate from the main floor. Repairing/replacing the main floor on a Trillium
is extremely difficult, due to the construction/design of the trailer. Hopefully it will just be that small area up front and the dinette in the rear. The plywood flooring on the dinette is separate from the main floor.
You will find threads on dinette area floor replacement. Its not too bad of a repair. I haven't seen a thread on repairing the main floor on a Trillium 1300/4500 (the two models with everything fiberglassed in place).
Before choosing the Trillium I bought, I inspected two with serious main floor rot (I passed on both of them). Both were bought shortly after by other buyers.....
The pontoon design, also unique to Trillium, makes floor rot less likely. But when it happens, the remaining design makes repair challenging.
That corner area in the front originally held a toilet, no shower. Someone might have done a poor repair in that area, so perhaps the damage will be limited to that area. Fingers crossed.
Any new Trillium owner should also look up discussions on common Trillium shortcomings, like the belly band, window leaks
, body to frame bolts rotting away, and door hinge wood rot. I love my Trillium but it does have its issues. Surprising to me, the new Trilliums have not addressed these design flaws.
On the upper right side of the screen, is a tab marked "Manufacturers", click on that tab, then choose Trillium. There you will find most of the threads that have been written on Trillium trailers.
The other Trillium models are built differently, so repairs to them is different and not really applicable to the 1300/4500 models.
Good thread on dinette floor replacement: