I recently started to build a 14'x18' rectangle Gazebo, and I have a question after my wife descided on changing the roof from asphalt shingles to aluminum. For my 4 outside corner posts I used 6x6 cedar, and for my center post I used 6x8's. I used 2x10 for the beams and notch cut all of the posts to inset the beams. The roof will be a hip with an 8/12 pitch with a 4 1/2 ft. ridge beam length. Now that I've switched from asphalt to aluminum can I use 2x4's for the rafters, or should I stick with 2x6's as I origanlly planned for? The roof sheathing will be 1/2 cdx or osb with 30lb. Felt paper followed bye the aluminum panels.

The reason that I went with cedar posts is I plan on wrapping all exposed wood with aluminum coil trim, and I didn't want to have a chemical reaction using pressure treated lumber wrapped with aluminum trim.

Regards,

Quadrunner

By the time you cut a birdsmouth in a 2X4 you don't have any web thickness left and 2X4 rafters look bad. Stay with the 2X6. Also realize you have a dead weight of the OSB and felt paper and, although we don't know where you live, a snow load could easily collapse the roof. Assuming 16" centers and 18 ft. long, your looking at $50+/- more for the 2X6 cost. If you are doing 24"centers it's even less.

Are you building in an area where you will need to building permit?