Tammy wrote:I have a retaining wall that is 9' high, 6' wide and 36' long. I'm using landscape timbers that are 8' long by 5" wide and 5" thick. How many timbers will I need
A bit of confusion here Tammy... If your "wall" is 9' x 6' x 36', its not a wall, its a cube.
In any event, you timber dimesions are 8' by 0.416' x 0.416', so you can divide those dimensions into your area to get the number needed. I'm assuming that you can cut the timbers to length where they overlap, so I'd use somthing like this:
<based on a wall 9' by 36', ignoring the depth of the timber>
9'x36' = 324 Ft²
8'x0.416 = 3.33 Ft²
324 Ft²/3.33 Ft² = 97.35, or 98 Timbers