Spacing depends on WHERE YOU LIVE! If you live here in houston, there is no need to put that much of a gap between them, 1/8" should be more than plenty. The boards will shrink and depending on the moisture content at the time of install, will determine how much. If you live in an area with a lot of rain and not much heat (Oregon for example) you should put at least 1/4" between them because as they shrink in the heat, they will swell when wet especially when it is cold. Either way, it is not wise to have no gap between the boards. Otherwise, you will end up with a lot of debris that will be difficult or impossible to remove, especially when you go to stain or re-stain.
__________________
|