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Porch Roof Diaphragm To the Editor: The approach Harris Hyman used to stiffen a two-story cathedral ceiling wall with a porch roof diaphragm seems like a great solution (Practical Engineering, 2/95). In the past I've stiffened such walls from the inside by adding a layer of plywood on the inside before the drywall goes up. But this only helps prevent racking and doesn't help at all with wind loading like the porch roof does. One question: Since the wind pushes the wall in, it seems like the attachment between the porch roof ledger board and the wall framing is what makes this system work. In the author's design, what is the proper bolt size and spacing? Bill Coulbourne Alexandria,