What is the recommended size of box I should use to "Frame In" the bathtub drain for a basement rough install? I was thinking of using a treated 1" x 10" to make a 14" x 14" box. Will the 9 3/4" be too deep? I was also told to place a little concrete in the bottom of the box to prevent any water from seeping up through the box. Is this necessary?
Thanks in advance for any help.
Dan