A.Finish carpenter David Frane responds: It's tempting to use plywood to make big doors, but, unfortunately, it (even mdo) won't stay flat when exposed to the weather. Here are three other ways to make doors the size you want:
The best way is to make real stile-and-rail doors. But that requires skill at joinery and better stock than you can get at most lumberyards. For doors this size, I'd want stiles and rails that were a minimum of 2 1/4 inches thick. You'd have to start with thick, dry material and use a jointer and planer to straighten it and bring it down to size...
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