How to Prepare a Redwood Deck for Staining

Scrub the deck with warm water and mild detergent. For large decks, a power washer will speed the process. Apply the detergent with a garden sprayer, then power wash until the wood is clean.

Use a heavy-duty detergent such as trisodium phosphate (TSP) mixed with 1 cup bleach per gallon of water and TSP mix if the deck is heavily stained or mildewed.

Restore the color of the redwood if it has become weathered and gray by mixing 4 oz. oxalic acid crystals (a wood bleach) per gallon of water in a plastic bucket. Apply the mixture with a large paint brush. As it dries, the wood will lighten and lose the gray color. Once it's dry, rinse it with a hose.

Allow the deck to dry at least two days if you're going to use an oil-based stain.

Find and set proud (loose) nails or screws by running a sponge or rag mop over the deck. It will snag on nail or screw heads that have popped above the surface. Reset them with a power drill or nail set.

Sand the deck. This is an optional step but will give you a superior, smooth, even finish. Use a power sander, starting with 50-grit sandpaper and finishing with 80- or 100-grit sandpaper. Vacuum or sweep the dust from the deck, or use a leaf blower to remove all the sanding dust from the grooves.

Stain the deck using a large deck brush for the most even finish.