How to Prepare Your Deck
Most homes now enjoy extended living space outside, usually in the form of a deck. To keep your wood deck or patio looking good and to extend its life, it is important that it be coated or protected and maintained regularly. Staining exterior wood is a process that, when a certain protocol is followed, can be a successful and rewarding experience.
Most of the decks built in Ontario are made from either pressure-treated lumber or cedar. Wood that comes from the lumber mills usually has what is called “Mill Glaze” present. Mill Glaze is the polishing effect caused by the spinning of the blades when the lumber is cut. The blade spins at a high rate of speed, creating a shine or glaze and effectively closing the pores of the wood. Unless removed, this glaze will not allow penetration of product.
The biggest problem we have seen through the years is not necessarily that the product used was of poor quality, but the preparation and application was done incorrectly.
For best results, you must mechanically sand all walking and horizontal surfaces. Use 50-grit sandpaper on walking areas and 80-grit on all other areas. Hand sanding the surface with a sheet of 50-grit sandpaper will not prepare the deck properly. Mechanical sanding is best. Palm or belt sanding is absolutely the only way to achieve the surface preparation needed for a successful long-lasting deck.
If walking areas are sanded properly, the product will penetrate the surface. If not, the product will float or sit on the surface, creating a skin-like finish. This will allow water and moisture to get between the product and the wood, causing cracking and eventual product failure.
Pressure-washing a new deck is recommended by many deck-stain manufacturers, but we disagree. This method of prep should only be used when cleaning or removing old products from previously coated decks. Sanding the wood after cleaning ensures that the wood grain is open. This will allow the coating to penetrate.
Once the sanding step is complete, the next important thing is to ensure the deck is dry enough to stain. We recommend that you wait 3 − 4 days after the last rainfall or washing.
Never apply stain in the direct sunlight. When the sun hits the wood directly, it heats the surface to a temperature higher than the air temperature. When stain is applied to a hot surface, the drying process starts too quickly and the stain will not have enough time to penetrate into the wood fibres. Apply stains in the shade or early in the morning or later in the afternoon when the sun is at its coolest. Usually one coat will do – even if the manufacturer recommends two.
Brushing is always the best way to apply stain. Apply one coat evenly across from left to right, one or two boards at a time. After you complete two full strips, look back. If you see any product still floating on the surface, brush it off immediately or wipe lightly with a rag. This ensures that the stain has penetrated the wood and is not sitting on the surface, which creates skinning.