It may be best to first define some terms used for deck finishing:
Sealer, Stain and Waterproofer are words you can use interchangeably and are single products. You don't apply a stain and then a sealer like you would an interior finish. These products are available as:
Clear which has no pigmentation and just seals the wood against moisture. This type of product lets the sun (UV) turn the deck gray. Toners which have a very small amount of pigment and offer minimum UV protection. Semi-transparent which allows the grain of wood to show through but has a richer color and better UV protection Solids which are more like paint hiding all of the wood's grain. These products also do not penetrate the wood. There are also classifications of finishes. For simplicity, they can be narrowed down to two types: film forming and penetrating. A film forming finish will form a barrier over the wood. At first, this type of finish offers the best protection (while it is intact) Unfortunately, outdoor elements and moisture quickly cause this type of finish to expand and contract at differing rates than the wood. This causes the finish to lose it's integrity and quickly break down into a peeling mess.
Most professionals prefer to use an oil based, penetrating, semi transparent sealer. These seem to have the best balance of longevity, durability and ease of maintenance. From this author's personal experience I stay away from anything that is not oil based. Water based sealers offer no conditioning for the wood. (Think of the way an emollient softens your skin and keeps it moist versus water that lays on the surface of your skin then evaporates away) The downsides of course are odor and cleanup.
Another type of sealer is called an acrylic. These types of products are not friendly for exterior surfaces. They are film formers so they crack, they peel, they flake, they cause wood to rot from the inside out, they are very maintenance intensive and if you ever decide you want to remove them be prepared to spend a hefty amount. If you have seen commercials on TV for 5 and 7 year "guaranteed" sealers, these are acrylics. I watch these commercials and just shake my head in disbelief. I have NEVER seen a sealer last for seven years, nor five years for that matter. I strongly recommend anyone reading this article stay away from acrylics. You'll thank me in the future.
Where To Buy Quality Products
I would avoid anything you would see at a home store. Products like Behr and CWF have a host of inherent problems like cheaper pigmentation and mildewcide. My recommendation is to go into a paint store like MAB, Sherwin Williams, Benjamin Moore etc. You will see products made by Cabots', Sikkens SRD, Deckscapes, and TWP. Follow the manufacturer's recommendations on temperature, amount of coats etc.
Application
Again, first read the manufacturer's directions on application. Some common methods include brushing, rolling, spraying or using a stain pad. Your goal should be even application with attention paid not to leave any puddles or shiny spots. Oil based penetrating sealers are best applied heavily, allowed a short time for penetration into the wood and then brushed out to remove excess. Following the proper steps for cleaning, pH balancing, and choosing a high quality sealer will give you longer life without the inherent problems from mold or finish failure that seem to plague many homeowners.
Where To Buy Quality Products
I would avoid anything you would see at a home store. Products like Behr and CWF have a host of inherent problems like cheaper pigmentation and mildewcide. My recommendation is to go into a paint store like MAB, Sherwin Williams, Benjamin Moore etc. You will see products made by Cabots', Sikkens SRD, Deckscapes, and TWP. Follow the manufacturer's recommendations on temperature, amount of coats etc.
Application
Again, first read the manufacturer's directions on application. Some common methods include brushing, rolling, spraying or using a stain pad. Your goal should be even application with attention paid not to leave any puddles or shiny spots. Oil based penetrating sealers are best applied heavily, allowed a short time for penetration into the wood and then brushed out to remove excess. Following the proper steps for cleaning, pH balancing, and choosing a high quality sealer will give you longer life without the inherent problems from mold or finish failure that seem to plague many homeowners.
