What is the spacing between boards?

Hi Kate, thank you for reaching out and for your interest in Trex! The minimum spacing between width-to-width of the boards is 3/16". If you are using the hidden fasteners that will automatically create a 1/4" gap for you. End-to-end, end-to-width and abutting gaps can differ, please reference a 2021 installation guide. Give us a call if you need any assistance (1-800-289-8739) or reach out to your local Lowe's ProDesk for assistance. Thank you, Trex Customer Care Team