A good cleaning’s in order for your deck

Published 9:00 pm Wednesday, July 19, 2006

Beautiful summer days turn a loving couple’s thoughts to … deck cleaning.

A wood deck is pretty much ignored all winter and spring as it patiently accumulates mold, mildew, algae, fungus, tree sap, bird droppings, rot, UV radiation from the sun and debris deposited by shoes and wind. The result can be a mess in the summer when it’s once again time to lounge around.

Decks can be made to look lovely again for the loving. What’s needed is a good cleaner and some elbow grease.

First, inspect the deck for damage. If there are rotted boards, these need to be pulled up and replaced. Use galvanized nails or special deck screws. Normally, deck builders leave about an eighth of an inch of space between the boards. Once the boards shrink in the weather, the gap is just right for junk to fall through but feet to feel no slats.

The first step in cleaning a deck is to get the crud out of the corners and cracks. Sweeping is better than washing with a hose because the water expands the wood. To pull stuff out of the cracks, use an old hand saw. The teeth are just right for the job, and the saw doesn’t have to be sharp.

Next, check for protruding nails or screws and loose bolts that hold the supports together. Then cover any plants around the deck with drop cloths so they don’t get scorched by the cleaning chemicals. Sand any rough spots with 40-grit sandpaper and finish with a finer 80- to 100-grit paper. Sandpaper as fine as 140-grit may produce a finish too fine for the sealer to penetrate.

Beware of using steel wool on a deck. It can leave behind iron particles that rust and discolor the wood. If this happens, the deck can be removed with oxalic acid.

Cleaning and brightening chemicals often include chlorine-based bleach, or sodium hypochlorite, which is used in pulp mills to break down the lignin in the wood. It can do the same to a deck. Other cleaners include phosphoric acid, trisodium phosphate or its substitutes, and disodium peroxicarbonate, or oxygen-based bleach. These are all rather nasty.

One of the best alternatives is 30 Seconds outdoor cleaner. It’s safe around plants if you wash them off within 10 seconds or so, and the 30 Seconds folks claim that it is biodegradable, photodegradable and thermodegradable. It also kills spores than can cause regrowth of the nasties. The dilution rate is 1 part cleaner and one part water, and it can be applied with a pump sprayer or sprinkling can.

For particularly bad spots, scrub the cleaner in with a brush or broom.

Don’t use a wire brush or you may get rust stains. Allow the solution to soak in, then rinse thoroughly and let dry – as in totally dry. If you use a pressure washer, use as little pressure as possible or you may get the furries little hairs of wood that stand up all over and need to be sanded back down.

A cleaned deck usually needs 24 to 48 hours to dry before sealing, though some sealers can be applied to damp wood. But the wait is worth it in the final result.

Sealing usually means restaining the deck. Beware of using a different product on top of the old stain or you may get bubbles in areas where the old surface pops up. The choices include clear water repellent that allows the wood grain to shine through but may not offer much UV protection against graying, splitting and warping; semitransparent stains that still show the grain and texture of the wood; and solid stains that coat the deck like paint but may not hold up to heavy traffic.

Whatever the choice, the process will likely have to be repeated next year, wood decks being what they are.

Jim Kjeldsen is a former assistant news editor at The Herald who now owns and operates La Conner Hardware Store in La Conner.