Use standard 5/4 cedar decking boards for your roof deck. This will provide a solid foundation for the remaining two layers. Install the boards so that the good face is turned toward the ground. The underside is visible and the top side is not only out of view, but will be covered by felt and wood shingles.
Gazebos are a fairly traditional garden structure used for outdoor entertaining. They are defined by their solid roof and open sides, are typically free standing and can have from four to eight sides. Our gazebo plans feature a traditional octagon pattern. Gazebo construction is more complex than most deck building, due to the angled framing and eight sided structure.