I have a ranch home on a crawl space, the garage is seperated from the home by a 6' wide breezeway. I'd like to, for starters, get rid of the wooden gate that serves as the entrance into the breezeway and install a wall and door to make it look more like part of the house from the front.

Do I build the wall/doorway with 2x4's and put that right onto the concrete breezeway? Wouldn't that be likely to rot as it gets wet or will it be okay?

Any tips for getting started with this would be appreciated. I've included a picture of the area that I'm talking about.