The patio under our deck was a damp, shady area and prone to mildew.  We never used it, except to store our daughter's old playground after we bought her a new one.  We wanted to make better use of the space and decided to transform it into an outdoor living area.  We hired Hilltop Home Repair to install an aluminum under decking and were very pleased with the results.  Here's the ceiling before:

This is the ceiling during installation:

 

Extra flashing was added on the upper deck level to prevent any leaks.  The ceiling is complete and new ceiling fans were installed.

 

We should stay nice and dry on the patio now.  Next, David is building a sectional couch for the area.  It is a work in progress...