Hey guys, this is my first post, so sorry if it is in the wrong spot. I am planning on building a mini greenhouse out of timber and polycarbonate sheeting. The timber is obviously going to be getting quite wet, so would need to be naturally rot resistant. I plan on using screwed mitre joins to join everything. What timber would be best, maybe cedar or Teak?

I was planning on cutting a 6mm slot in some 3" x 1" to house the polycarbonate. Can you buy timber with the slot already cut, or do I have to do this myself?

Cheers
Dave