I think we need more context to answer this question. To deck can mean to lay down a wooden floor or it could mean to punch someone.

The person is suggesting that a wood surface should be the next step in this construction project. Pilings are posts. He says a flat surface (usually wood) would rest on top of the posts. Next he is saying a support can be extended out farther and again a wooden flat surface should be placed on top. In central United States a deck is an area behind a house where people relax on outdoor furniture. Many pieces of good quality wood are laid on a support structure. It is an outdoor floor. It would be the size of a room. Some decks may have a sun shade over them.

I agree that it's difficult to understand the meaning from such a small clip and without more context. I could not tell what it meant.