[dsraven]

sounds like you need a "pole barn" style, with a dirt floor etc. just to park in. water and debris from vehicles simply gets absorbed into the dirt. a buddy of mine is building one. laminated treated 2x6 for the poles, because they don't split and twist like a 6x6 would, then the rest of the above ground stuff is regular timber. the span between the poles can be bigger than you would expect and then the unit is strapped horizontally at 2 ft intervals, lots of guys use metal sheathing screwed to that but you could also use regular sheathing and side it to match the rest of your buildings. the roof gets sheeted and then a membrane top to bottom, like normal, with rolled asphalt on top. nothing pretty but functional. for coastal areas the asphalt could be swapped out for tile or galvanized steel but tile can absorb moisture and make the roof heavier than normal plus the trusses would need to be engineered for the extra weight. galvanized steel can go dull pretty quick. you could look into the metal roof systems, like decra. they claim to be very good for coastal areas and are coated for resilience in the salty air etc. a couple of big doors or a big single, depending on your width. if you use a scissor truss style and center the door opening you can have a normal looking roof line and a taller garage door with regular height walls. a lot of guys use them when they plan on having a hoist but restrictions dictate a max height to the top of the shingle. you kinda lose space on each side of a hoist but if you just need access for a taller truck, with no hoist in the middle, then it might work.
just some thoughts.