Do I need to leave any gaps between the siding and the siding trim?
Please keep in mind that because of the expansion and contraction nature of our material, there would need to be adequate spacing built into your installation. As a result, when installing in cold weather, you will want to build space for the boards to expand, and when installing in hot weather, you will want to install in such a way that the boards can contract, without issue. Allowing your boards to acclimate to their environment before installing would serve as best practices. Detailed expansion and contraction values can be found on page 7 of the decking installation guide here: https://www.newtechwood.com/pdf/Decking-Installation.pdf. Keep in mind that this is the gap needed on both sides of the siding board.