On Jun 9, 7:40*am, wrote:
I would like to cover the ceiling a porch with something. *What is
there now are 2X4 appearance "beams" spaced 16 inches apart. *I like
the look of bead board, but am thinking that the 1/4" thickness isn't
substantial enough. *It may end up sagging.

So what I thought I might do is cover the area with plywood first,
then attach the bead board to the plywood. *Or, attach (glue?) the
bead board to the plywood first then install over the ceiling.

Good idea, bad idea?

By the time you do a plywood backer and a beadboard sheet... your
expense and time will be more than just getting tongue and groove
cedar or pine. T&G doesn't sag and doesn't require a plywood backer
and you can stain it whatever color. Also the typical beadboard sheet
is just masonite, it will be wavy and it probably wont weather nearly
as well as T&G, and with sheet masonite you'll have to deal with
hiding ugly seems, more time.