The message .com
from "Fash" contains these words:

For making it better for storage just put a raised floor in to keep
stuff away from the damp. Nothing sophisticated just a platform and
keep it away from the walls. Use treated timber and it should last a
fair while, and of course don't store stuff that is likely to go mouldy
in the high humidity.

No need to go to the trouble of putting in a raised floor. Wooden
pallets are very useful for keeping stuff off damp floors and should be
easily available and either cheap or free.

--
Roger Chapman