Lowe's had the primed MDF boards at the sizes that best suited our space. We needed eight 1x3x8's for the vertical (which we would cut exactly in half) and six 1x4x12's for the base and chair rail. For anyone new to lumber dimensions the width and thickness are NOMINAL sizes. A 1" thick board is generally 3/4" thick (depending on if it is wood, composite, or MDF). A 3" wide board is actually 2-1/2" wide and a 4" wide board is actually 3-1/2" wide.