Thanks Colbyt. For the small gap I leave between the wood body of the shed,
and the concrete ramp, should I then fill in that gap with a polyurethane
sealant and cement backer rod, or something like that or is that where the
mastic expansion joint comes in? How much of a gap are we talking 1/2 inch?
Thanks.

How about air? Air makes a good filler, and it's cheap too.
What are you going to do, fall down the crack?