Last year I rebuilt my benches using 6×6 posts and Trex, a laminated composite decking board that has a very long life…and a very low compressive strength. It nearly immediately bowed across the span of 7’, and while I had hoped this expensive solution would also be a long-term solution, I have found it necessary to replace them in just over a year.
So this time, I am replacing the Trex decking with 8’ long 2×10 treated pine. Before placing them, I used a tinted semi-transparent decking stain, slate color.
My garden has 3 of these 8’ benches, along with a few monkey poles, and a u-shaped bench also made of Trex, which has shorter spans and can last a bit longer. For now, the 3 bench tops will be replaced with wood.