AdamusLignus The ones that I have seen had bamboo double layered & crisscrossed & palm fronds laid over that. I have seen some used that some company sells. It was bout 15 - 20 or so ago on a project. I keep thinking I some homemade too, that looked pretty good. I don’t know why maybe you could not just use the bamboo put in place first vertically so to say, over purlins or horizontal directly over the rafters, then another layer crossed over in the opposite direction, then a final layer vertical (from gutter edge to ridge). Then dried in place & sealed with something like CWF or something. I would not use it for the main house, but for a gazebo or something it would probably interesting, fairly long lived, inexpensive in your case, & fairly watertight with lots of ventilation. I suppose if you wanted them to carry off more water faster, you could split the final layer so it would be like trough, so to say.