How to Waterproof a Deck With Fiberglass Cloth & Resin

Prep work

1). Lightly sand the deck to remove the weathered (grey) surface layer and restore the original color of the wood. Pry out and break off any large splinters that may be present.
2). Mix a small batch of body filler and fill the splinter damage. Allow the filler to harden fully then sand the patches flush with the surface of the deck.
3). Mix slightly larger batches of body filler, then fill the gaps between the planks of the decking or the gaps between the edges of the sheets if it is a plywood deck. Allow this to harden fully then sand all filled places flush with the surface of the deck.
4). Don protective gloves, then mix a moderate amount of fiberglass resin with acetone to thin it down to a consistency that will soak into the wood. Add fiberglass catalyst to the resin then immediately roll a light coat onto the decking. This will soak into the wood and seal it, preventing dry spots in the fiberglass lamination caused by "thirsty" wood drawing the resin out of the cloth before it hardens.

1). Roll the fiberglass cloth off of the bolt to cover the area to be glassed. Cut the cloth with sharp scissors to prevent fraying of the cloth and move over one cloth-width. Butt the adjacent strip up to the edge of the preceding one. Continue until the area is covered. Roll each pass up individually then store in a convenient location so it is readily available but not in the way.
2). Mix a batch of resin with no thinner added then catalyze it. Roll the resin onto the deck exactly where the first pass of cloth will lie. Lay down the first pass and stretch it taut so all wrinkles are pulled out of it. Roll a coat of resin onto this pass and insure that it is thoroughly wet with no dry or light spots.
3). Repeat the process with each successful pass. Start each pass while the resin from the preceding pass is still wet and not hard. This will help to marry the edges and make a smooth, fair surface. Continue until the entire deck has been glassed. Allow this to harden fully before walking on, using or otherwise touching the area.