This is my plan of the day:
Like on many boats, our gas locker is very wet. We need to raise the floor above the water line, to prevent further rot.
Surveyor and others recommend welding. This will involve cutting to gain access...I think it'll be done in a few years, when the boat is out, and we may epoxy the hull.
As an interim, I was considering materials. I've read that people have used concrete, and even Kingspan!!
My thought was to use something like this:
http://www.robinsonsequestrian.com/liquid-rubber-floor.html
It bonds with steel, is designed to resist impact and vibration, and is, indeed waterproof.
Plus, we wouldn't need a rubber mat in the locker!
If I were to clean up, weld the vents shut, and cut higher ones, and then pour some of this in, would I make my life better, or worse?