Decks, Patios, Porches and Docks - Sealing a porch

We want to fix up our basement but in order to do so we must first seal the porch. The basement extendends under the the porch, it is not a crawl space, the porch is covered. The basement is cement block. The porch is wood and sits on top of the blocks. There is weather proof carpet on the porch but the boards are not sealed and it is not sealed to the blocks. When the wind blows just right the rain comes in where the porch meets the block.
How can we seal the porch?