When boards are placed end to end, should I leave a gap?
It depends. If you expect the boards to contract (that is, it will get colder in your area from when they are installed), you may place the boards end to end to allow for contraction. Conversely, if you expect it to get hotter in your area, please leave a gap to allow for expansion. Specific recommendations can be seen in the chart on page 4: https://www.newtechwood.com/pdf/Decking-Installation.pdf.