Maximum horizontal span for a 2 x 4?
With ZERO LOAD on horizontal 2x4's, what's the maximum span without zagging when 2x4's are attached to the front and to the back of two 8-foot tall 4x4 inground (cement footings) posts. (Outdoor use, all pressure-treated lumber.)
This is what I'm looking to do: Use two 12-foot 2x4's attached horizontally (near the top) to two 4x4 posts that are spaced 10 feet apart.
Would I need a third (middle) post? For looks, I want to avoid a third post. 2x6's for the horizontals is NOT an option.