[villagetinker]

Wow, I am amazed that an existing birdcage would support all of the weight associated with a wood and shingle roof. I would suggest you have a architect review your proposal before you proceed. I have read articles were owners have replaced the screen roof with canvas or a "water shed" screen, but in these cases you would not be adding significantly to the load of the structure. I think you would be adding significantly to the wind loading with the canvas roof. Please do some additional investigation before you proceed.