[Gulfcoastdude]

I'm building a new 24x36 pole barn, 6x6 posts with steel trusses spaced 12'. Will 2x4 purlins be okay spanned 12', or should I use 2x6's? The purlins will be spaced 2' and the roof will be 26 gauge metal. I live in south Alabama, so there's no snow load here.

Also, there are a few low spots in the concete slab where I notice the water pools. What would be the best way to build up these low spots? I'm using this for a three car carport that will eventually be enclosed to make a garage.

Thanks.