What is the range of C4's explosion? What is the optimum placement of C4? I'm assuming placement on the line between two foundation tiles and two wall tiles does maximum damage.
With the newest Update declared in Devblock 66, C4 range against environment will be 1. This is the same, as it was in legacy. So C4 will damages only the very object it's placed on (a wall, a door,..) and not the surounding.
However, range versus player is higher. If they didn't change it with this update (And the changelog doesn't mention it), than ~2,5 foundations are enough distance to not get damage.