Maybe think of your porch floor a little more like a roof ... I, too, have an old house with incorporated porches (front and back) that sit over top of a full basement foundation (brick with original stucco.) We restored the back porch as a "sunroom" (it was closed in some time in the 30's) and I noted that roofing tar paper was used between the sub floor (plank) and the original T&G porch floor. There are shreds of roofing tar paper hanging on the edges of the bottom of the front porch floor where I can find it, but the old wooden floor was replaced with plywood and then the porch floor was tiled by POs (a bad DIY with 1 inch grout lines that leak like crazy, making my repair job that much more difficult.) The pitch on both porches is good (away from the house) There are low shingled walls all around the porches so water would be trapped without some sort of system to remove it. The front porch uses a pitched trough with 2 exit tubes at the foot of the short wall but I found no evidence of this on the back porch. These 2 devices (the roof paper and the trough) surely would have worked well if they were maintained, alas, the metal trough is rotted thru and leaves/critters were getting into the basement till I discovered the holes and band-aid-patched them till I can address repair of the trough properly. (interestingly, the front porch foundation was hidden behind a finished wall in the basement and was only found when we had a termite inspection done.)

mkesow, no expert here, just another homeowner working on water drainage correction. Proposal one is not preferable to exterior water drainage correction. That leaves #2 and #3. Regarding #2: "Quote 2 Local contractor says he would do an external french drain system. Dig an approx 7' deep trench 2' wide, put drains at the footer, tar/vapor barrier the foundation wall, backfill with gravel, replace window wells. $3,000." If you go this route, a couple of points: tar is just damp proofing-different from water proofing applications. Also it does not expand to fill new cracks, nor does tar which inevitably will occur. It's recommended now to use an expansile wall surface product, with elastomeric properties. Elastomeric membranes are a polymer modified asphalt, formulated to remain pliable. Also, vapor barrier 6 ml, even 2 ply are considered minimum. heavy gauge polyethylene dimpled drainage may be better, and bentonite membrane best.

Try 'flat roof solutions.' EPDM joints are made with seam tape (uncured EPDM that comes in a roll and sticks by itself). You will need toluene to clean the surface before using the seam tape. Other solvents can damage the EPDM, but toluene is available in quart cans at a paint store. Be careful with the seam tape. It sticks to everything, including the tool you are goping to use to cut a piece off the roll.

Keep fans running 24/7 to dry out the crawl space. There is no reason the trades can't do their rough-in work prior to encapsulation of the crawl space. Indeed, doing the rough-in work first will let you seal any penetrations in the foundation after they've finished. Install sacrificial polyethylene sheeting on the soil surface if you need to for their work and replace it afterwards with a heavier duty material when the crawl is dried out and encapsulated. A preemptive note to Mark Bischak: installation of "sacrificial" polyethylene sheeting is not a religious ceremony; the only deaths expected are the dinosaurs who died long ago to create the hydrocarbons from which the polyethylene is derived.