The Pleasures and Pitfalls of Deck Sealing

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After a long day at work, I often find comfort and peace just sitting around on my deck.
I have outfitted this space to be my own, with plants, nic-nacs, and of course, my grill.
We even had a hot tub installed, sunken into the deck for ease of entry.
My contractor built the deck with pressure treated lumber and decided to wait until the deck needed a sealer before applying any treatment to it.
You see, pressure treated lumber (often called salt treated), is permeated with a preservative to prevent rot, so left untreated it will last for nearly twenty years without rotting or damage from termites, or so they say.
What really happens is that the wood will eventually become very dry, opening up cracks and shooting up splinters; not the best surface for running around barefoot.
After time, nails will back out and poke up from the constant expanding and contraction of the wood.
If you are noticing these drying effects on your deck you may want to consider using a sealer to preserve the integrity of the wood.
After all, who wants a deck you cant go barefoot on? Often with projects such as this, after you get into it --or should I say in too deep--you realize you might need help.
(I personally suffer from the insidious carefully-read-directionitis gene deficiency.
) I might be able to steer you toward your goal if you heed these suggestions and warnings and if not, call me, advice is always free.
Please heed suggestion number one if your pressure treated lumber is not stamped KDAT, you should wait at least six months before applying any acrylic finish or sealer, this includes any type of paint or stain.
Chemical leaching and drying out of the wood will cause peeling and possibly other types of material failure.
The next thing you should do in this project is choose a product that is right for you.
There are an endless variety of sealers which can be used, some of which are marketed aggressively.
You have probably heard of Thompsons sealer and others, but just because the marketing is good, it doesn't mean those products are the best.
Basically there are two classes of products for this application: oil based and water based acrylics.
Most products available to the consumer are of the oil based variety, and typically these products really last about two years with an initial application.
Look at the labels and take notice of how you should clean up your brushes and equipment.
If clean up is with thinner or mineral spirits, you are looking at an oil based product.
Acrylic based products typically last from three to eight years depending on the number of coats applied, and these products clean up with water and detergent.
As with any coatings material, these products each have pros and cons.
The longer lasting acrylic products cost more per gallon, and usually require additional coats in the initial application.
The acrylics also can be applied to a wet surface, which is actually a benefit since you always need to clean the surface before coating.
Acrylic products will allow you to clean the decks and seal them the same day, which is a major no-no for the oil-based products.
Oil based sealers must be applied to a clean, dry surface, so after cleaning, you will need to wait a couple of days before sealing.
Both classes of products will also come in a variety of colors, all of which are transparent allowing you to see the wood grain detail underneath.
These colors give you a wide variety of hues to choose from and I suggest picking up some samples to bring home.
Unless you want a clear sealer, you will want to see the samples next to your house to avoid having the sealer color clash with the existing siding.
Both oil and acrylics offer clear versions of the product, but beware especially with the oil based products; these will offer the least protection and longevity for the money.
As with all paints and sealers, the ultraviolet rays emitted from the sun are the biggest factor in the deterioration of the material.
These rays dry out the material over time and render the protection ineffective.
Oil based products in general do not weather nearly as well as their acrylic counterparts, so consider this when setting your budget.
Once you have decided on a product and color, you will need to determine how much material you will need to finish the job.
You do not want to run out of material in the middle of the job, this could cause unsightly overlap marks, which are virtually impossible to remove.
Measure the square footage of your deck by multiplying length times width.
Keep in mind that deck surfaces are usually sealed only on the top, where foot traffic occurs, but you may opt to coat the underneath as well.
If so, multiply your figure by two.
If you will be coating the handrails, you will need to measure those as well.
Measure the length of the rails in their entirety.
Then measure the height from the deck surface to the top of the cap.
Multiply the length times height and the multiply times two, to account for both sides.
If you will be sealing other things such as band boards or lattice, measure them as well then and add up all of your figures all to arrive at a total square foot figure.
This will determine how much material you will need to finish the job.
Each material will have slightly different spread rates and you will need to read the labels of each to determine how many square feet per gallon each product will cover.
In fact, if your budget is tight, you may want to measure before deciding on a product.
Now that you have your materials, you are ready to clean the decks.
You will need to use a chemical to kill any mildew, and possibly a brightener if your decks are grey and weathered.
This chemical step is critical, even if you dont notice any visible mildew.
Mildew is a microscopic organism and is often invisible in the early stages of infestation, but must be killed before applying any coating.
If left alive, the mildew will continue to grow through the sealers film and then will be virtually impossible to get rid of, short of stripping the material and starting over.
I recommend a combination of mildewcide and brightener, and personally prefer Flood products.
You can find a dealer near you online, but all major manufacturers produce similar products.
Before applying the cleaners, you will want to protect the surrounding surfaces as required by the products label.
Most cleaners will kill plants and grass if they are left unprotected, but if you keep them wet throughout the process the chemicals are usually diluted sufficiently and no damage is sustained.
Always read the labels carefully and apply the warnings to your situation to avoid damage.
If your deck has been stained or sealed before you will probably need to strip the old material from the surface.
If your deck has been sealed and you simply want to use the same product and color, you can usually apply another coat after a thorough cleaning.
The most common way to apply these cleaners is through a power washer with a chemical pickup tube.
If you do not own a power washer you can easily rent one from your local paint supplier or hardware store.
Ask the dealer to give you a quick lesson on its usage, and be sure to ask specifically how to use the pickup tube.
Mix your chemicals in a five gallon bucket and put the pickup tube into the mixture.
With the chemical applicator tip on the wand, apply the chemical to all needed areas and wait about ten or fifteen minutes.
You will see the wood return to its original color right before your eyes.
After the prescribed time, begin rinsing the chemical thoroughly.
To rinse properly without damaging the wood surface always use the least harsh power washer tip and keep away from the surface of the wood.
If needed, you can get closer to the surface to remove thick buildup of mildew or other contaminants, but beware, most power washers will irreversibly damage wooden surfaces if you get too close or use too harsh a tip.
A good rule is to always use the least amount of pressure needed to get the job done.
You will want to avoid making the wood appear fuzzy.
Continue to rinse the surface until your rinse water runs clear and is free of all yellowish color.
Lastly, rinse all surrounding plants and grass.
If you have chosen an acrylic sealer, you are now ready to apply the base coat of sealer; if not, clean up and relax for a couple of days.
Before applying any sealer, you will want to protect all of the surrounding surfaces that you do not want to get the material on.
Realize that the sealer will drip down through the deck boards, and you may need to cover any concrete or other surfaces under the decks with drop cloths.
Also, depending on your application method, you may need to protect some of the siding or trim that might be over-sprayed if you choose a pump-up type sprayer to apply the material.
Pump-up sprayers are often used to apply these materials since many homeowners already own one for spraying herbicides and pesticides.
Be sure to clean out the sprayer thoroughly before and after use--these materials can clog the tip irreversibly and ruin the pump if not cleaned properly.
If you are brushing, buy a large brush, either 6 or 8 inches, and maybe even one that fits on an extendable pole.
This will allow you to do most of the work in a standing position, dipping out of a five gallon bucket.
Either way read the label on the material and apply it according to the directions with the appropriate number of coats and drying times.
You want to avoid stopping the application in the middle of any given area and starting again once the surrounding area has dried a bit, as this will cause unsightly lap marks.
They can be avoided by starting in a corner and running two or three boards in their entire length.
If sealing the handrails, do those first and partially cover the deck to avoid dripping; those drips will also turn into a type of lap mark that is not easily repaired.
Generally work from top to bottom and work quickly.
Again, pay close attention to the label and recoat as recommended with the appropriate drying times between coats.
Refer to the label to see how long you should wait before replacing any furniture or planters.
I used an acrylic sealer on my decks, rails, bands, posts, and lattice.
While the acrylics are more expensive, and harder to apply, it will keep me from doing the decks every two or three years.
Whatever you decide to use, follow these suggestions and you are sure to enjoy a great looking deck for years to come.
If you enjoy this column and have any suggestions for topics or questions that you might like answered, please write me at info@beachpainting.
com
, or call us at 252-441-8224 ask for Jim.
James Ashe is the owner of Beach Painting Contractors, Inc.
He resides in Kill Devil Hills and is the President of the Outer Banks Chapter of the Painting and Decorating Contractors of America (PDCA).
For more on decks and products to be used click here!
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