A major source of problems and complaints for all wood finishes is over-application of the coating. Many do-it-yourselfers and some painting contractors believe that when it comes to coating, more is better. This is simply not the case and is particularly a problem for decks. Most deck finishes are designed to penetrate the surface of the wood. Putting too much of these coatings on the wood leads to a buildup of material, forming a film which can ultimately peel or crack. For water repellant products, over-application can result in a surface which is overly waxy, sticky, or slick. Over-applied stains will often result in sticky surfaces, since the coating buildup interferes with their ability to dry properly.

Surface Preparation: Proper surface preparation is an important factor in the ultimate performance of coatings for pressure-treated wood or any wood surface. Surfaces should be clean, dry, and free of mildew before coatings are applied.

Application Methods: Clear Coatings can be applied by a variety of methods including brush, spray, roller and pad. Brushing is considered to be the best technique for detail work such as spindles and railings. However, for large horizontal deck surfaces, spray application is quickest and easiest. Either airless power sprayers or pump hand-held sprayers can be used. It is important when spray applying finishes to back brush or back roll the wet coating. This evens out the finish and eliminates drips and lap marks. Pads are also well suited to coat decks. Individual boards should be coated along their entire length to prevent lap marking. Paint rollers are more suitable for applying siding finishes than for deck coatings. However, they can be used successfully to apply clear finishes and water repellants to decks. As for most exterior coatings, it is vital that deck finishes be applied under proper weather conditions. Solvent borne coatings are a bit more forgiving than water-based formulations and can usually be applied when outside temperatures are in the range of 40-90°F. Water-based products should not usually be applied if outside temperatures will fall below 50°F within 24 hours after application. Deck coatings ideally should not be applied if precipitation is forecast for the 12-24 hour period after coating. This will prevent the possibility of water spotting or wash-off. Once they dry, of course, these finishes will be resistant to precipitation.

Label Instructions: Since each commercial formulation is a little different, the manufacturers label instructions should be consulted and understood before the product is used. This is important not only from an application and performance standpoint but also with regard to user safety and environmental considerations. Unfortunately, many consumers fail to read the product label until after they experience a problem, at which point it may be too late for easy corrective action. Wear Proper Clothes: To protect against skin irritation, a long-sleeved shirt, long pants and goggles. Also use an OSHA approved mask to protect against inhalation of vapors if using solvent based products.

Depending upon exposure, application technique and deck use conditions, water repellants and clear finishes can perform for up to two years before the need to recoat. Since these are transparent finishes, application is usually easy, requiring no more than one to two hours for the typical deck.

Stain Application Guidelines:
Prior to use, mix all cans together to insure uniform color, (referred to as "boxing")
Even If you are using a standard factory mixed color you should not eliminate this step. You need to be assured that you are starting out with the same color and even factory mixed colors can vary from batch to batch.
Take an empty 5 gallon pail and add up to 4 gallons of stain, mix thoroughly using a long 3' or so 1" x 2" or mixing paddle.

Routinely stir during application. When you get down to the 1-2 gallon level add another gallon if you are using a large amount for the total job. By adding new material at intervals like this small color differences will not be noticed if there is a small difference in color between batches. Before applying stain, test on a sample piece of wood from your deck or in an out of the way place, to verify the color and look you want.
Apply between the temperatures of 50° and 90°F. Do not apply when hot, wet or windy weather conditions are expected within 36 hours. Always wait for moisture to dry before application.

Method of Application:
Apply liberally to dry wood to the point of saturation, two coats applied wet on wet are ideal, this allows the wood to soak up as much as possible. Do not allow to puddle, remove any excess after 10 minutes or so. A separate dry applicator can be used for removing excess.

The preferred application methods are: a quality paint brush, an airless sprayer (rentable) a pump-type garden sprayer, stain pad or a short nap roller, 1/4". Individual boards should be coated along their entire length to prevent lap marking.

The wood coating should saturate all checks or splits. All exposed ends should be coated several times until all wood pores are saturated.

Care and Maintenance:
Stained wood surfaces may need to be retreated every 2-3 years or earlier depending on weather exposure.
A close inspection of treated surfaces should be done annually.