Building a garage...need help

[tonyk72]

I'd like to build a garage/large storage shed underneath my deck...as cheaply as possible. I'm not looking to have insulated, just dry.
I have a 10x20' to work with & have about 8' of height. I need advice on how to waterproof under the deck. How do I keep it dry without building another roof under there? I have some ideas, but would like to hear what you guys have to say.
Also, I have a septic tank that is just outside the deck. My concern is should I have a concrete foundation poured just inches away from the tank? This would also be right up against the house, how would a 10x20' concrete foundation affect the foundation of my house? I was thinking I just level the area and put some plywood down.

 

[vette-dude]

My upper deck is over a concrete lower deck and I installed corrugated plastic sheets screwed to the upper deck joists. You overlap the edges and using formed dividers to match the corrugations you can give them a slight downward slope to let the water run out the end. Sounds screwy but it works well and everything stays dry. They usually come in 2 x 8 sheets and it is relatively cheap. You can use rubber washered screws or silicone the screw heads just to be sure they don't weep in a heavy downpour.

Randy

PS: You can then install a gutter at the end of the plastic panels and run the water away from the house and the septic tank.

 

[Piet]

If your Desk is built correctly... it slants ever so slighty away from the house... Use a sealed decking material (Like a Vinyl deck) and put eavestrough at the end of your deck. Run some lighting underneath. You could use soft sides (tarps) or wood walls.

Try using Asphalt for the floor instead of Concrete... It is Not as Hard, but can be removed fairly easily.

Is that what you are thinking?