Is there any way you can seal off the old patio to keep the skunk out?  A neighbor is having serious skunk issues this year but fortunately he lives in a very rural area.  After having their house dogs sprayed a couple times in years past he is fed up.  I guess if you catch a feral cat you could take it for a ride, if they are locally owned cats seems to be no issue to just release them.  From my experience skunks are not stupid and learn quickly however they have a tendency to not be to fearful of people.  

Skunks are nocturnal so try to use that to your advantage, skunk seem attracted to lighted areas around dust to dawn lights where they will eat bugs, might try placing your trap nearby.   Skunks will be active after rain showers at night which provides another opportunity to catch them out and about.  

Good luck, no fun dealing with consequences.

I've caught them in box traps. Make sure you put hay or grass on the bottom otherwise they won't go far enough in to trigger it. Also put the trap in the biggest garbage bags you can fit and then tarp over it.

I've caught many this way using potted meat, canned chicken/tuna. You might get a cat or possum but they can be released easier.

I either gassed or drowned the skunk but you can take your chances opening the trap to release it somewhere alive.

Don't use meat, you'll likely just end up with cats. Get some old donuts from a Dunkin donuts dumpster or something. Works great then sprinkle some oil of anise over them. The anise is extremely strong smelling and will attract animals from a long distance. Put rocks or something at the end of the trap to keep stuff from reaching in through the cage and grabbing the bait. Happens a lot with coons. I don't like those new types of traps like havaharts, but if that's all you got.

I have no idea where you are at with the skunk, but is it possible the mice are eating the marshmallows, keeping the hair trigger from being set off? I've had many cat food and marshmallow baited bucket sets cleaned out in such a manner.

I usually smear the trip plate with peanut butter because it is fragrant and is hard for animals to get by reaching through. Wrap the trap in an old blanket so only the door in is exposed. If you catch something you can just walk up to the trap and carry it wherever you are taking it, as I have never had a single skunk spray when they were in the trap covered with a blanket. Usually I then prop the door open and stand way back and blast em far far away once they are a fair distance from the trap

This whole endeavor sounds about as risky as EOD work, just not deadly once you get that thing trapped.

Seal everything except for the spot you put the box trap (secure it well).  If the skunk is under there, it has no where to go but out, into the cage.  If you catch some cats, then just release them and reset.  I've done that numerous times for skunks and opossum.

Eric  

Late at night, when the skunks should be out and about, I would throw several moth balls or better, quantities of moth "ice" under the patio. Skunks don't like the smell of that stuff.

I would then stuff all the entrances under the patio with big wads of chicken wire, snipped so that it has a lot of wire points to stick any critters that would try to get in. You may have to secure the wads of wire with staples or nails so the skunks can't push them out of the way.

Also, I would "mark your territory" (when appropriate) as skunks shy away from the scent of human pee.

That seems to keep the skunks out from under my house, although they still spray the dogs in the yard.