Ask the Builder

Crash course for new homeowners on cleaning and sealing decks

When staining a deck, homeowners must decide whether to have a tinted or clear finish.
When staining a deck, homeowners must decide whether to have a tinted or clear finish. (Tim Carter)
By Tim Carter
Saturday, June 5, 2010

DEAR TIM: I just bought my first home, and I need to learn how to stain a deck. I have so many questions. For example, how do you clean a deck before you start? Is there a difference between deck stains? Should I just paint my deck instead? Are there decks that don't have to be stained? -- Jamie F., Nederland, Colo.

DEAR JAMIE: Let me start by saying that it's impossible to completely cover this topic in one column. But I can give you a crash course on cleaning and sealing a deck that will yield you great results over time.

Let's start with selecting a stain. You can get at least two types of deck stain or sealer. One type is a penetrating finish that is designed to soak into dry wood. Other deck stains are formulated to perform much like varnishes or urethane. These products soak into the wood, but they also form a film on the surface much like a sheet of plastic wrap.

The problem with these film-forming deck stains is that they almost always peel when they eventually fail. The peeling is unsightly, and when you go to re-stain the deck, you must completely remove or strip off the old film. As you might imagine, this can be a tough job.

I prefer the penetrating deck stains and sealers that don't peel when they fail. It's easy to prepare a previously stained deck for re-coating if you have a penetrating finish on the deck.

Next you'll need to decide whether you want your deck to be a color or prefer having a clear finish. I happen to prefer colored stains that are a medium shade of brown. Some people love a clear look that shows the natural color of the wood from the mill, while others prefer the gray look you see on weathered boardwalks or fishing piers.

The pigments used to color a deck stain perform a very important job. They help to absorb the ultraviolet (UV) light from the sun that bleaches out the natural color of wood, causing it to turn gray. Some clear deck stains contain ingredients that also act to block the sun much as the sunscreen lotions we put on our own bodies.

I tested the latest clear technology deck sealer last year, and it failed miserably. The cedar wood where I applied the sealer looked great for a month, but then it started to turn gray. Within four months, my cedar was so gray it looked like a neglected fishing pier.

I complained to the sealer manufacturer, and they sent me three different ones to test. I applied the products about a month ago, and I'll know more by the end of the summer. I posted a video on my AsktheBuilder YouTube channel that shows me applying these deck stains.

You need to clean all wood surfaces before you apply deck stain or sealer. This cleaning process is meant to get rid of all dirt, weathered sealers or stains and damaged wood fibers that might be barely hanging on at the surface.

Many people promote the use of pressure washers when cleaning a wood deck. If you apply too much pressure, use the wrong tip on the cleaning wand or hold the tool too close to the wood, you can cause serious damage. The enormous pressure easily erodes the soft springwood that's between the darker bands of summerwood. To get the wood smooth again, you have to sand the deck. That's a tremendous amount of work.

I've found that cleaning the deck with oxygen bleach is a less aggressive method that works well. Don't confuse oxygen bleach with the household chlorine bleach you might have in a white plastic jug in your home. Chlorine bleach takes the natural color out of wood, it's highly toxic to all vegetation and trees around your deck, and it can accelerate the corrosion of metal fasteners and structural connectors.

Oxygen bleach has none of these bad characteristics. It's a powder you add to warm water. The oxygen ions that are then released in the solution are powerful cleaners that deep clean the wood. It's best to apply the oxygen bleach to dry wood so it soaks in, deeply cleaning the wood.

Tim Carter is a columnist for Tribune Media Services. He can be contacted via his Web site,

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