One of the more fragile elements of concrete blocks is the bottom, since when submerged is exposed to the adhesion of marine elements and its weight considerably increases with them, which causes over the years detach and fall to the bottom.
One strategy to avoid this problem is to leave the bottom of polystyrene concrete module without any protection because the snail and other wildlife normally does not adhere to the same.
By using high-density polystyrene of the water absorbed by the foamed polystyrene over the years will not assume the 5% volume so that the loss will be minimal freeboard.
Anyway, if we seal the bottom of the pontoon to ensure durability of the installation can use a layer of SPF as seen in the video below.
