how wide should shelves be in the closet
November 30, 2006 4:43 pm. Iâve made bookcases in different widths with no supports between the gables. The widest one Iâve made has 86â³ wide shelves and exhibits zero sag. I make my stuff entirely out of MDF and never use screws or nails. As you probably know, MDF has no grain and canât support its own weight.