Originally Posted by dalepres
But I also would not want to create a wet spot that remained wet a lot.
Yeah, but how often will you use it?
But you need the ground to slope away from the house for 10 or 12 feet. I wouldn't run the shower into the foundation drain, but you could run drain pipe in the same trench. You could also make a drywell.
I still wouldn't worry about the T-111, but if you did want to use soap and shampoo, you could rig up a shower curtain that would protect the siding. Just a couple tea cup hooks maybe -- hook it up to use it, and then take it down.
Another idea would be to put some metal roofing on the side of the house. Two sheets of 5V would probably handle most of the splash.