Guide to Sealing Indoor and Outdoor Wood 

 October 29, 2020

By  Dale Keese

You have been working on a wood project for several weeks now and it is coming to an end. You have poured hours and hours of sweat and tears on weekends in your backyard and are finally proud of your handiwork. But even after so many weeks of toiling, you feel something is lacking.

Deck with a Sea View

Slowly, it dawns on you that you have done all the rough work, but forgot about the finishing. A wood finish will not only make it appear richer and deeper but also forms a sort of film on the surface that seals the wood.

Essentially, the pores of the wood are sealed and stained, giving it a smoother, more even look and feel. Wood finishing also protects it from the elements. If this is not the first time you have worked with wood, you would probably know the importance of the processes of sealing the wood and staining it. However, a lot of people are confused between the two processes and often mistake one for the other.

While staining will enhance the look and feel of the wood, sealing will protect the wood from rotting and other elements. Let us quickly clarify how different these two processes are once and for all.

  • Sealers are applied to the outside of the wood and its main purpose is to repel moisture and make it waterproof. This is done because moisture in the wood can lead to rotting and fungal growth.
  • Sealers have limited ultraviolet ray protection, so the color of the wood can turn to gray and fade, leading to splitting and cracking.
  • Sealers can be applied to any wood surface and can be applied using a paintbrush.
  • Sealers need reapplication from time to time but are easy to apply. They do not need much expertise and may need to be reapplied every year, depending on the quality of the sealer.

What is a Wood Stain?

  • Stains go deep inside the wood, unlike sealers that are applied to the surface.
  • They can change the color of the wood because they contain pigments.
  • Apart from some water-repelling qualities, they also protect against UV rays and are available in opaque, transparent, or semi-transparent variants.
  • They are more expensive than wood sealers but can last much longer.

There are products available on the market known as stain-sealer combos, which will do both jobs in a few coats. Now that we have established the differences between the two, we can continue our article about wood sealing.

No matter what your purpose of sealing the wood is, you want it to last a long time and hence you need to seal it properly. Wood sealers can be put into two categories: acrylic or water-based and solvent or oil-based. Let us take a look at these.

Oil-Based vs Water-Based Wood Sealers

The most common question when someone suggests any of these two sealers is: What is the difference? In effect, both of these sealers act as an extra layer on the wood, protecting it from damage and elements. Remember that these layers are not permanent and will show signs of wear over time.

Standing in the Rain

The most common and basic sealers are made up of polyurethane, which is plastic. It is also available in a lot of varieties such as satin or glossy. It is mostly used for side tables, bookcases or tables, and desks; that is to say, any wood structure that is to be used indoors.

Let us look at both these sealers based on their properties.

  • Color: A water-based sealer has a clear hue, while an oil-based sealer will be slightly amber. The water-based sealer will retain its clarity over time, meaning it will not cloud or color, while the oil-based sealer will turn darker and will continue to do so.
  • Durability: This is something that has been a topic of debate for hardware store owners. Both types of sealers vary somewhat when it comes to durability. But if good-quality products are used, this difference is barely noticeable. The misconception is that water-based sealers are “weaker”, but it has been proven several times that if applied properly and taken care of, these can last as long as oil-based sealers.
  • Odor: You will barely notice when a water-based sealer is being applied in the house. It has no smell, and you would not need to wear a respirator. You and your pets can remain in the house while a water-based sealer is being applied. On the other hand, an oil-based sealer has a caustic smell that can seep into your clothes and cling to you for hours. You would need to wear a respirator while applying an oil-based sealer. Also, it would be ideal for the house to be vacant or well-ventilated for the same purpose.
  • Heat-Resistance: Water-based sealants, save a few exceptions, are generally used for wood structures that are not exposed to extremes. They cannot handle heat or chemicals well. Oil-based sealants have better resistance to heat and hence can be used on kitchen tables.
  • Texture: With an oil-based sealer, two coats are all you need but they tend to develop dents since it is soft in density. A water-based sealer is a harder coat but needs three to four coats, depending on the wood surface and the quality of the sealer. Usually, experts use three coats of the sealer, regardless if it is water or oil-based.
  • Time to Dry: You can apply many coats of a water-based sealer in a day, usually three to four coats in the same day because it tends to dry faster, in say, about four to six hours. On the other hand, an oil-based sealer usually can only be applied once a day because of its thicker consistency, and hence, needs a longer time frame to dry.
  • Cost: Oil-based sealers are usually cheaper and you can get a five-gallon can for about $120 to $150, whereas a water-based sealer would cost $200 upwards for the same quantity.

While talking about sealing or finishing woodwork, you may have come across terms such as lacquer, varnish, shellac, and polyurethane. Though these names are used in the same vein, they have different uses. The common factor between them is that they all make for excellent sealants.

Experts will tell you that there are countless ways to seal the wood. But they will also say it is not as straightforward as just picking up a product and following instructions. If we dig deeper, we will find that different kinds of materials can be used on different types of wood. Let us take a look at these.

Minimalist Furniture


This is one of the most widely-used products used for sealing and finishing wood because of the gloss it leaves behind. It adds a warm, amber color to wood and is thinner than other finishes. Usually, one coat of lacquer is sufficient. Lacquer is made up of plant or synthetic resin, which is dissolved in alcohol and is available in a variety of sheen.

One of the reasons it is such a popular choice is because it dries fast approximately between 15 and 30 minutes, and is scratch resistant. But one of its drawbacks is that it tends to turn yellow over time, which could be unwanted if the wood it is being applied to is light in color.

It can be either sprayed on or can be applied using a brush. You should be warned that it emits strong fumes so open windows and keep the room well ventilated before you work.


Shellac is a natural product that has been in use for a long time. It is made from the secretion of an insect that is typical in Southeast Asia, specifically India and Thailand, which is scraped from wood bark and the flakes are treated with alcohol. Applying this on wood not only gives it a protective layer but also adds an amber color.

One of its major drawbacks is that it is not heat-resistant and will crack or flake if exposed to intense heat. Shellac can be applied by using a brush.

Shellac dries pretty fast, from 30 to 60 minutes, which means you can also touch-up if you feel your handiwork is lacking. It blends in with most types of wood shades easily. Most of the time, shellac is used on woodwork and trim.

Applying Varnish


The varnish is another popular material that is not only used with wood but also other surfaces. It is generally used as a topcoat for a shiny finish and can be used for outdoor wood projects because it solidifies into a hard shell and resists yellowing. In addition, it provides UV protection.

Overall, varnish is a great all-around, easily available, and popular choice because of its wide usage on almost any kind of surface. They do not have a very hard finish, which means they can withstand any sudden changes in the temperature. You should not apply it on antique-looking wood furniture though since varnish tends to look "plastic-y", which may ruin the desired effect.

They are usually available in clear or lightly-colored finishes and some variants are known to discourage the formation of mold or algae. For this reason, varnish can be used on outdoor projects which have proximity to water, such as beach chairs and boats.

Applying varnish is easy. Just take care and never shake the container too vigorously before use. Shaking the container leaves too many bubbles inside, causing cracks in the finish after drying.

You may find upon opening a varnish container that it already had formed bubbles. This can be easily rectified by thinning it a little by using mineral spirits and stirring it gently. This will make the varnish easy to apply on most surfaces.

Creating Your Own

You can make your own solution by mixing turpentine oil and varnish. This simple solution is versatile; the oil penetrates the surface of the wood and the varnish does what it is supposed to do. It is a win-win solution if you are feeling adventurous, and you do not need any special equipment to do that.

All you need is a clean cotton cloth and work over the desired area. It spreads easily and smoothly and dries off fast enough for you to put in more coats. You do not need to worry if you find you have put excess solution; you can just wipe it off with another clean cloth and let it dry.

Wood Sealing Instructions

Now that you know the differences between oil- and water-based sealers, we trust you will make an informed decision when it comes to sealing your wood projects, which brings us to the main event: how to seal the wood.

In this short tutorial, we will assume that you have already decided on a sealer that is suitable for your needs, whether it is a water- or oil-based sealer. If the surface you are going to use it on is of a lighter shade, we recommend that you use a water-based sealer because it is colorless and will enhance the natural look and feel of the wood. Unless you want to make the surface look very glossy, avoid an oil-based sealer.

Make sure that the sealer will also limit dirt build-up and protect against UV rays. While selecting your sealers, you should always read the instructions on the back of the sealer’s container to see if the manufacturer advises wearing any safety gear. Regardless, if you are doing a DIY seal wood project, you should always wear safety gear such as thick rubber gloves to protect your skin and a mask to prevent you from inhaling toxins.

Living Room

Required Materials

  • A high-grade oil and water-based sealer of your choice
  • A brush with natural bristles
  • A few pieces of wood
  • Sandpaper (different grit varieties, from 100 to 400)
  • A small bucket (to use with the sealer)


  1. 1
    We are assuming that the surface that you want to seal has recently been painted. You have to make sure that the paint has completely dried off and that it is not sticky to the touch. If it is, you will need to set it aside and let it dry completely before you can seal it.
  2. 2
    If you are using a water-based sealer, do not stir it too vigorously when you pour it into the bucket. Doing so will create bubbles under the surface of the sealer and will stick to the brush when you put it in. These bubbles will prevent a smooth application of the sealer. Be gentle with the brush and squeeze out the excess sealer back into the bucket. For the same reason, do not shake the container vigorously.
  3. 3
    Apply long, slow, and even strokes. Start from the middle and work your way to the edges. If you think you have left out some areas, do not worry. Let the sealer dry off first and then cover with a second coat. Do not paint over the wet sealer immediately. This is applicable to both water- and oil-based sealers.
  4. 4
    Do not go overboard with the layering or coats. Too many layers or over-enthusiastic strokes will end in disaster for this project. Your work will show that you were hasty in the application and the seal may look superficial and obvious.
  5. 5
    Let the sealer dry completely and try not to touch it. You can check after a few hours just to be on the safer side and if it does not feel wet, it is ready to use.

Now, let us move on to bigger subjects and find out how you can go about waterproofing a deck.

Wooden Deck Sealing Instructions

If you happen to have a wooden deck, you are probably aware that it is a great asset to any home. But you are also probably aware that wooden decks would require proper and constant care. Taking care of it would ensure that the deck has a longer lifespan and looks as good as it did on the first day.

If the deck is new, experts suggest that the deck should be left to weather and dry for as long as three to nine months before you can seal it.

Working on Wood Floors

Cleaning the Deck

First off, the deck needs to be cleared of algae, gunk, dirt, and sediments that have settled in. You can go about it in many ways. If you have a small deck, you can get this accomplished the old-fashioned way by getting on your knees and sanding out the rough parts thoroughly. You can sweep it thoroughly afterward before applying a deck cleaner (completely optional).

Another efficient way to do this is by using a pressure hose (do not set this to very high because you may end up damaging your deck). Clear the deck of any equipment, tables, and chairs to do this. Go over the deck thoroughly with the hose and wash away anything that has attached itself to the deck over time, such as debris and mud.

Once you are satisfied that the hose has done its job, use a palm sander to smooth away all the rough edges, splinters, or kinks that may have developed.

If you are not satisfied with your cleaning efforts, you may want to follow it up with a deck cleaner. These are readily available on the market. You can even make your own with available materials in the house. Here is how:

  1. 1
    You will need a bucket that can accommodate a regular broom or, ideally, a deck broom’s head. Fill the bucket halfway with warm water and add two and a half cups of oxygen bleach. Avoid chlorine bleach because it can be harsh on deck boards and cause discoloration.
  2. 2
    Stir until the powder dissolves and disappears. Add half a cup of mild liquid dishwashing soap and stir and let it sit for a bit.
  3. 3
    You may want to cover any shrubs or plants using clear plastic sheets before you clean the deck. Though the solution you have made is pretty mild, you should still take preventive measures.
  4. 4
    You can either use the broom or a paint roller to apply this solution to your deck generously. What you will be doing is saturate the deck with this solution and letting it get in the spots that are difficult to get to. Work the broom or the roller to work up a little lather too and work your way from one corner of the deck to the other.
  5. 5
    Once you have cleaned the deck to your satisfaction, leave the solution on for up to 15 minutes. If you have used a commercial product, follow the instructions at the back of the container.
  6. 6
    Rinse the deck with the garden hose, albeit, with less pressure. The deck needs to be completely dry before you start sealing it. This may take up to 72 hours depending upon the weather.
Food Styling

Working with the Deck Sealer

There are several sealing products available on the market (for this specific purpose) at online or hardware stores. Prices vary from $30 to $45 per gallon. Most of these are versatile products that can be applied to a variety of wooden structures such as patios and fences as well. They are either water- or oil-based or made up of natural ingredients.

Most of these sealers have UV blocking or waterproofing qualities and are available in transparent or opaque formulas. Choose a seal that retains the natural color of your deck.

Since you have already cleaned and sanded your deck, you do not need to do any more preparation. Although a final sweep after it is dry could go a long way as you may come across loose screws or exposed nails. What you should do though, is check the weather forecast and choose days with moderate weather. Let us start sealing the deck.

  1. 1
    You may need to protect your siding or railings. Tape them off with masking tape or painter’s tape so as not to get the sealer on them.
  2. 2
    Use a bristle brush to apply the sealer thoroughly across the surface of the deck. You can use an alternative applicator such as a roller, but a bristle brush is much more effective since you can go between the boards.
  3. 3
    Work in strokes, covering three to four boards in one go. Work carefully, and try not to drip the sealer too much on the boards since the splotches will stand out and will be difficult to get rid of.
  4. 4
    Be thorough and be patient because this may take a while. Follow the manufacturer’s instructions. You may need to seal the deck twice, but not more than that.

Now that you know how to seal and waterproof wooden structures, here are some tips with regards to how you can protect your investment and keep them looking good.

Atrium with Hammock

Tips for Maintenance

  • Seal Regularly: Whatever you are using the sealant on, make sure to reapply the seal at least once every two years. Remember that wood is nature’s product and hence, is vulnerable to temperature changes, moisture, and UV rays. Sealing becomes all the more important if the wooden structure is outdoors, such as lawn chairs or a deck. Sealing will add more years to the wood and you will need to use a good penetrating sealer with it.
  • Clean Regularly: You will not want dust to settle on your wood furniture or deck. Clean away the dust particles and any other impurities as regularly as you can. A daily wipe is recommended but once in two to three days is also enough.
  • Clean Stains: If you have stubborn stains on your furniture, you need to clean them off before you set about sealing it. You can make a simple oxygen bleach paste to tackle it. Just mix one and a half teaspoons of bleach in a quarter bowl of water until the consistency is paste-like. Apply this paste on the stains and leave it on for 15 to 30 minutes. Rinse it off and repeat if necessary. Sealing over stains will make them difficult to get rid of later.
  • Avoid Paint: Some guides will tell you to paint over your furniture or deck with paint. This is a lazy practice and would spell disaster later. Eventually, the paint will start to bubble, crack, and peel off under harsh conditions. This means you will have to keep repainting every season. On the other hand, oil-based sealers fade naturally and are not harsh on the wood.
  • Don’t Let Moisture Settle: Take care of outdoor wood structures and furniture. If you live in an area that sees a lot of snow, you should be shoveling it off as soon as possible. The same goes for indoor furniture. Avoid spillage, but if it happens, wipe it off immediately. Not doing so will trap the moisture in over time.


This concludes our extensive guide on sealing and waterproofing wood. You can now identify the various sealants and their usage. In most cases, a good quality sealant will do the job, but remember to do it every two years or so and do not ignore regular maintenance. We hope that you found this article helpful and will help you tackle sealing jobs around the house.

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