Building a wood arbor around stucco garage doors.Whats the best way to attach corbels and ledger to stucco?

Question:this is a dbl 16' door with a 24" jog wall between the doors. There's plenty of meat to anchor to, so should I just pre-drill and use some big lag screws on the corbels and the back ledger? How can I make sure it won't leak? Is there some metal flashing I should use between the wood and stucco? I'm supposed to be doing this tomorrow. When I've mounted corbels it was always before the lathe went on and we just papered behind it, so I'm not exactly sure about this. Carpenter for 20 years but never too proud to ask or learn new things. Thanks for any help.

Answers:
best solution would be to cut out stucco with masonry blade on skil saw to allow ledger to fit against wall framing then metal flashing and caulking . you could just apply lots of caulking behind ledger when you install it and then just lag into existing framing (easiest)