This porch was built next to my house, but they never put walls on the
crawl space (of the house itself), behind that porch.
The crawl space on the rest of the house is made from 2x6s nailed to
the posts which support the house. The 2x6s run horizontal, and are
covered with metal siding (pole barn metal), which goes 6 to 8 inches
into the soil. Apparently they built this porch before they put the
siding on the house crawl space, so that portion of the house is wide
open.
Ok, it's not "Wide open", because they built this porch from treated
framing, put deck boards on top, but also put these deck boards on the
sides, down to the soil. However, they left an opening to get under
this porch, which I temporarily covered with plywood, using a few
screws so I could remove it easily.
While this partly closes things up, there are the gaps between the deck
boards, Plus they did not put backs on the steps, so if I look between
the steps, I can see right under the house. Besides letting cold aur
under the house in winter, it lets critters get under the house, and
whatever rain and snow that can get down there.
The plan is to move the porch about 3 feet away from the house, put
the metal siding against the crawl space wall, and move the porch back
where it was.

Why move the porch at all? It seems like it would be easier to just climb
under the porch and add your metal siding underneath the porch. You might
have to add some support framework, dig down the 6" to bury the metal in
the ground, and possibly cut the metal to size. That still seems like a lot
less work than trying to move a porch and then get it back in place.

Alternatively, run the metal siding around the outside of the porch. Remove
the steps if necessary then reinstall/rebuild them when you're done.

Also, if your deck boards are wood, I would think about removing those that
run down the sides to the soil. Wood in contact with earth is a bad idea.

Anthony Watson
www.mountainsoftware.com
www.watsondiy.com