Is there a spray to keep wasps from building nests on my porch?

https://www.youtube.com/watch?v=ODvfMBJUL0U

There are lots of products on the market that are listed for wasps. They can be found at garden centers or anywhere that sells insect/garden supplies.

Probably not. They seem to built nests where they want! But--you can remove the nests very carefully. Before you attempt to do that you should do some research on what are the best ways so that you don't get stung.

No, but you can buy wasp spray for after they nest.

Here are 2 of the top 10, spray early spring. We did under our deck railing where they were thick, they get one whiff and keep on going.

Here in the South, we paint our porch ceilings "Haint Blue" ("haint" is slang for "haunt") because it is believed that birds and insects will not build nests on blue surfaces, as they perceive it to be sky, and therefore, not a solid surface. As to the "haint" part, in New Orleans, it is said that vampires and other evil spirits would come to your home, see the blue porch ceiling and think it was daylight, and retreat at once! (Apparently, evil things are also really, really stupid!) :-) But anyway, any shade of sky blue will do, and I have honestly never seen nests on blue ceilings -- although I thought most of these critters were color-blind. Hmmm.