What Keeps Cats From Urinating on the Outside Doors and on the Porch?

Clean the whole porch using a mix of 1 part distilled white vinegar with 2 parts water. Room temperature or slightly warmer water is best. Scrub or spray everything, including the walls, the screen doors, the floors and even the outdoor furniture. Let it air dry and then wash everything again. Cats will pee in the same area over and over again if they can smell urine. The vinegar will get rid of the smell and make the area less attractive.

Make the porch less of a party ambiance. Let's face it, right now it's probably fun for the cats to hang out on your porch. Get rid of hiding spaces, comfy cushions to sleep on and areas where the cats can hide from the rain and cold. Don't feed your own pets outside. Even if there's no food left over, the smell might attract cats to your porch.

Buy cat repellent at your local pet store and spray it only where you don't want the cats to urinate. This won't keep the cats away from your porch, but they'll hate the smell enough to avoid getting close to where you've sprayed. There's no guarantee they won't pee against a different wall, but at least your screen doors will be safe. Red pepper flakes are messier but cats also hate them, so you can sprinkle them on your porch if you can't find cat repellent.

Install a motion-activated sprinkler. Unless cats are permanently living on your porch, they have to get there through your yard. If every time they try, they get wet in the process, they'll soon be out looking for better party digs.

Put a giant piece of chicken wire or aluminum foil right against the outside of the doors before you go to bed. Cats are more active at night, and chances are they're urinating on your porch while you're sleeping. Cats have sensitive paws and they'll hate the feel of metal. In the morning, simply pick up the metal and put it aside until the next evening.