A properly applied stain or sealer is part of regular maintenance to protect your deck from stains, mildew and damaging rays. Sealers and stain products exist for almost every type of deck, including pressurized wood, softwoods and even composite decks. Selecting the appropriate product to match the deck material and applying it the proper way will ensure a long-lasting, good-looking deck.

Stain or Sealer

Sealers are clear products that protect against moisture but do not offer protection against the Sun’s damaging ultraviolet (UV) rays, which fade a deck. Stains are basically tinted sealers that provide color and UV protection—the darker the tint, the greater the UV protection. Stains are sold under names that indicate the darkness of the product, from clear transparent sealer, to semi-transparent, semi-solid and solid. A solid stain is more like a coating and may hide the grain of the wood while a semi-solid or semi-transparent stain will allow grain and texture to show through. Distributors may also add pigments to customize the color of the stain to match exterior features like fences, sheds or siding. When purchasing more than one can of stain or sealer, mix the product into one receptacle prior to application to guarantee a consistent result.

Composite deck manufacturers sometimes recommend treating a deck with a protector or finish to guard against the stains, mold and mildew that can plague these decks. Some stain manufacturers carry a line of stains and protectors made specifically for composite deck materials.

Stains may also contain additives to enhance performance. Some stains contain mildewcides and fungicides to retard the growth of mold and mildew. Others include citronella to repel mosquitoes.

Oil-Based and Acrylic-Based Stains and Sealers

Stains and sealers may be oil-, water- or acrylic-based. Professionals like Mark Crump of Be Clean Pressure Washing Services in Richmond, Va., typically prefer an oil-based stain. “I personally don’t use water-based stains,” he says. “I prefer an oil-based stain that penetrates the wood rather than sitting on top of it.”

Acrylic or latex stains tend to be thicker and are often marketed for their quick turnaround time. “Some of these acrylics let you wash the deck in the morning and stain it in the afternoon,” says John Sundquist, owner of American Deck Maintenance, Inc. of Northbrook, Ill. Unlike oil-based stains, which can harbor molds and mildews, an acrylic stain is inert and will not provide food for mold and mildew growth. However, acrylics are relatively new to the stain industry and some professionals have avoided using them. “Acrylic has a long way to go,” says Sundquist. “It has only been on the market for a few years.” Whether it is better to strip an old acrylic coating or apply a new coating directly over the old one is still open to debate.

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