A composite board product according to the present invention is formed from a core of coarse wood components disposed between a pair of cellulosic fiber webs. This assembly is compressed to consolidate the board product and to provide an indented margin thereupon. The board product is provided with a rounded shoulder where the margin joins the rest of the product in order to preserve the continuity of the tough skin formed by a cellulosic fiber web. The margin edge is preferably rounded off on the side of the board product opposite the indented margin, and the tough skin formed by the remaining cellulosic fiber web is folded over. After trimming, only a narrow edge of doubly densified wooden core is exposed to the weather.