How to seal a deck (or fence)

How to seal a deck

Most all decks (and lumber fences) have one thing in common;

Nearly every one of them is built structurally with "pressure treated" pine; this includes support posts that go into the ground and pretty much all of the framing underneath. If it's a fence, the posts are almost always pressure treated pine.

Pressure treated is lumber that has been soaked in chemicals under pressure so that the lumber resists insects and rot - for a while.

Deck skirts, flooring, railings, balusters, and steps might be a different type of lumber altogether, or a composite type of lumber, pressure treated pine, white pine, or something else entirely.

Lumber fences are usually pine, but sometimes they could be made of cedar.

Methods of sealing a deck (or fence)

"If all else fails, read the directions"

When it comes to sealing any kind of lumber, there is one important rule regardless ofwhat type of sealer (or stain) you are using,  and regardless of what your method is when applying the sealer: 

   •  Do not overapply - even though you think it will be better and last longer - because you're wrong.

All manufacturers of deck sealers have instructions labeled right on the container.

These instructions tell you what types of surfaces you can apply their sealer to (including fences), how many square feet the product will cover (in a perfect world), and they tell you how to apply their product, along with clean-up procedure and material safety.

For the novice, it is very important that you read & follow those instructions, which include cleaning the deck (or fence) first.

There are three different ways to apply sealer; Brush, Roll, & Spray.

• Brushing

Brushing sealer is highly proper and will work with any sealer. It is also very laborious and time consuming, but it does ensure that the sealer gets into the pores of the lumber, and it helps to spread the sealer evenly. Some manufacturers specifically state on their label to brush their product only.

• Rolling

Using a roller to apply sealer is perfectly fine with most sealer manufacturers. A roller can apply sealer much faster than just a brush, however, you will still need to use a brush to get up near the house siding and for areas that a roller can not get to, and you will need a brush to use for the final strokes - to work the sealer into the wood pores.

• Spraying

Spraying deck sealer is just too awesome. Most sealers approve using a garden type pump sprayer, or you can leave the spraying for the pro's who have the proper spraying equipment and tip sizes. 

The goal...

The goal of applying any sealer is to keep water out and / or protect from U.V. rays. Regardless of which method you choose to apply your sealer, it is recommended that you use a brush to deliver the final strokes and work everything into the pores, and to even everything out.

Don't think for a moment that you can just goop it on; too much sealer and it will crack, chip, flake, and peel. Too much sealer and your lumber can't "breathe", causing certain areas to rot underneath the sealer.

...also; when using a straight-up oil type sealer; whatever doesn't get absorbed into the lumber will just sit on horizontal surfaces (like handrails and deck flooring) and will remain sticky / tacky, sometimes taking weeks or even months to dry.

⇒  All lumber is different, the more tightly packed the pores are; the less sealer you will need. New lumber usually requires less sealer than old, sun baked, dried out lumber. Containers of sealer show how many square feet it will cover in ideal situations; older decks (or fences) are going to need  more.

  Make sure your deck has been cleaned, and it must be completely dry.

This does not mean to make sure your deck "looks" clean, it means that you must actually clean the deck because there is dust, pollen, algae, mold spores, etc.., and if you apply sealer over a dirty deck, the sealer might fail or discolor. Brand new pressure treated pine or cedar decks have "millglaze"; wood sugers forming a barrier created from the process of cutting the lumber - which needs to be removed.

If you are not going to get a professional to prepare your deck, you can use a bucket of deck cleaner solution found at the hardware store, a scrub brush, and a garden hose. 

⇒  Schedule this on a day when it will not be raining & temperatures are above 50° fahrenheit

⇒  Transparent colors may look different on new lumber Vs. old lumber; sample testing your color in an inconspicuous area is always a good idea to see how it will look. Allow your sample to dry, because it looks different when you first put it on.

⇒  You need to stir / mix your sealer - some sealers need to be stirred constantly while you are applying them.

Make sure your sealer has been shaken at the store, or you can use paint paddles to stir. If you have several gallons of the same stuff, "Box" all of your sealer together into a larger container. "Boxing" means to mix all the same product from individual containers back and forth, in order to achieve a uniform color. An easy way to do this; is to use a 5 gallon bucket to pour everything into, and then stir. You then can redistribute your sealer back into the original containers and put the lids back on until you need to use it, and you will be certain that every matches - even if you need to do touch ups later.

⇒  Do not apply your sealer in direct sunlight on a super hot sunny day - if at all possible.

How to seal a deck the right way

Check list

⇒  Ideally, have everything off the deck. This inlcudes removing bird feeders, tiki torches, wind chimes, hanging planter boxes, etc..

⇒  If you can't remove something because it is too heavy, try moving it to the other side of the deck, or aleast out of the way until you can finish the heavy item will eventually sit.

⇒  Once the sealer has been applied, you might be tempted to apply a second coat; make sure you follow the manufacturers directions. Applying a second coat the wrong way can lead to the sealer peeling, chipping and flaking, and some manufacturers don't recommend a second coat.

⇒  The very last thing you will be applying sealer to; will be the deck floor itself. The first thing you need to apply sealer to; would be any trellises and gazebos, then the deck balusters (including the inside and outside top & bottom rails - but not the top hand rail just yet).

⇒  It really doesn't matter if you start on the outside of the deck or the inside. A good idea is to do all the areas you really don't want to do first - that way; everything else is cake. Sometimes it helps if you have someone on the outside of the deck while someone is on the inside of the deck - to check for runs and get everything uniform.

⇒  Pay close attention to how the lumber is reacting to the sealer as you are applying it; if you see that the lumber is just sucking up your sealer, give it more - but only at this moment. If the lumber is not absorbing the sealer, push the remaining sealer into the next section you will be working on.

⇒  You want the lumber to "drink" all that it wants; but only right now at this moment. If it gets absorbed - give it more, but only right now at this moment. If the lumber is not absorbing the sealer - use your brush and push it into the next section you will be working on - do not leave any excess sealer on the lumber that is not being absorbed. Your final brush strokes go back into the area you just left - this creates a "wet edge" and eliminates any "start & stop" brush marks on the deck.


⇒  You can not stop what you are doing to answer the phone or stop to talk to someone unless you are at a "stop point". A stop point is when you completely finish a board or section of lumber. If you stop midway, you just might leave a "lap mark" which will be obvious when the work is done.

After you seal everything else, you can now do the top handrails of your deck, then do the deck flooring, then work your way down the steps. If you have no steps, work your way back into your patio door or over your ladder.

Contact us to do your deck - or if you do it yourself - Good luck!

**Although this page talks mainly about deck sealing, fence sealing is done exactly the same way.**

Same principle to seal a deck - just insert the word "fence" where it says "deck".