How to waterproof wood for outdoor furniture

How to Waterproof Wood Furniture for Outdoors ( Proven Methods)

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Last updated on September 11th, 2023

Whenever you are building a new deck or purchasing some new wooden furniture, it’s always a good idea to ensure it’s weatherproof so it can be able to withstand outdoor elements. Not treating wood makes it susceptible to warping, cracking and rotting when left in harsh weather. So, if you use your wood pieces for a long time, it’s essential you waterproof them. The real challenge, then, is figuring out how to waterproof wood furniture for outdoors.

The three surefire ways to waterproof wood include:

  • Using natural oils such as tung or linseed oil.
  • Applying thin clear coats of polyurethane or some other sealant.
  • Using a stain-sealer combo.

Applying these products to outdoor wood will help it retain its shape for a long time, which is a great way to save time and money! However, it will take a little bit of time and effort, which is no big deal compared to what you stand to gain. In this write-up, we will review the different methods for waterproofing outdoor wood as well as the benefits and downsides of using the products involved.

Why Waterproof Outdoor Wood Furniture?

Outdoor wood furniture left outside is at the mercy of the elements – sun, rain, snow, and even frost. This means that it can swell, warp, crack, fade and even rot unless it’s properly sealed or treated. And that might cost a good chunk of money to fix or replace. So, the question isn’t can you weatherproof outdoor wood, but how to.

Waterproofing outdoor furniture goes a long way to preserve its integrity. Not only will it keep it from rot but also protect it against UV rays, insects, frost, cats, and other unfavorable conditions.

This doesn’t mean your furnishings will suddenly become foolproof, but it will take a long time before you start thinking about replacing them. With proper maintenance, some can even last for more than two decades.

Waterproofing wood is not limited to your outdoor chairs and tables but also includes other wooden structures such as your deck, shed, and even fencing.

The importance of waterproofing wood

The major importance of waterproofing your outdoor wood furniture is to maximize the lifespan.

Wood is a porous material, so it tends to absorb water when exposed to inclement weather. Damage from rain and humidity can cause the wood to swell, warp, or even rot, thus decreasing its useful life. So, it’s essential to treat any wood that you intend to leave outside, even if it’s kept undercover on your porch or pergola.

When you fail to seal or waterproof outdoor wood, you’re simply setting it up to fall apart too soon. And this can be as early as the end of every humid summer. You might have no other choice but to get a replacement, which might not always be convenient. Perhaps, that’s not the best way to spend your money.

On the other hand, when you waterproof the wood, it will not only protect it from rot but also ensure it remains in pristine condition for a long time. As a result, you’re able to keep the furniture much longer.

How to Waterproof Wood Furniture for Outdoors?

There are basically three approaches to waterproof wood furniture for outdoor use. One of them is to use a sealant such as polyurethane, lacquer, or varnish. Another method is to rub the wood with natural oils such as linseed or walnut oil. Thirdly, you can apply a stain-sealer combo.

METHOD ONE: Using Natural Oils/Hand-rubbed Oil Finish

Natural oils have been employed for centuries and remain the easiest way to waterproof outdoor wood furniture. They are commonly used on dark-grained wood such as mahogany and walnut and do not contain any of the VOCs commonly found in synthetic sealants. As a result, they are the least toxic and the way to go if you want the easiest and safest solution.

However, natural oils seep into the body of the wood and so only provide moderate protection. So, they are best used on outdoor wood furniture kept in sheltered locations. They are usually applied in multiple thin coats.

There are two major types of natural oils – linseed oil and tung oil.

Linseed Oil

Linseed oil is available in three forms – raw, boiled, and polymerized linseed oil. Raw linseed oil offers the best look and protection but can take as long as two weeks or more to dry, making it less practical. Boiled linseed has a shorter drying time but releases harmful VOCs. They usually contain heavy metal or petroleum-based drying agents, which is responsible for the short drying time. Polymerized linseed is simply pure linseed oil heated to a very thick texture.

Tung Oil

Like linseed oil, tung oil is non-toxic and eco-friendly and often needs to be applied in multiple thin coats for the best result. It dries just about the same time as polymerized linseed oil and usually leaves a yellowish hue, which makes it ideal for light woods. Generally, it performs better than linseed oil because it creates a harder surface layer when dried.

Whatever natural oil you choose, you can blend them with other ingredients to hasten the drying time and eliminate stickiness. There are also pre-blended natural oil (linseed or tung) products available, which you can purchase to save time. A standard blend is usually made up of one-part oil, one-part polyurethane, and one-part mineral spirits.

Follow the steps below to apply a natural oil to wood:

  1. Start by stirring the oil thoroughly. Then apply it on the wood surface with a natural bristle paintbrush. Make sure the wood piece is sanded and cleaned before applying the oil.
  2. Allow the oil to settle into the wood, and apply more to any area that looks dry.
  3. Remove any excess oil with a dry clean cloth or rag. Then, give the wood a few hours to dry completely. We recommend allowing it to stay overnight.
  4. Next, sand lightly using fine-grit sandpaper; then apply the second coat following the same steps above. You can apply as many coats as you want, depending on the type of finish you wish to obtain.

NOTE: As earlier indicated, natural oils are best for dark-grain wood. For lighter-colored wood such as ash or pine, you’re better off using a sealant or stain-sealer combo. Also, you can reduce the amount of mineral spirits if you want the mixture to be thicker, or you can reduce the amount of polyurethane if you want to get more working time. For quick drying time and a glossier finish, add more polyurethane!

METHOD TWO: Using Sealants

Sealants offer better protection than natural oils because instead of penetrating into the wood, they create a hard-shell, glossy film on top of it. This film offers better protection against scratches and moisture but tends to peel away after some time. So, the wood needs to be sanded off and refinished. The major downside with using sealants is that they often contain harmful VOCs, which are not usually present in natural oils. So, you need a lot of ventilation when applying them.

The three main types of products you will find in this category are varnish, polyurethane, and lacquer. All three products are very popular and possess excellent waterproofing properties. They are also quick to dry (some take only 15 minutes) and can be applied using a brush or spray. It is best to apply them at room temperature.

Polyurethane

As the name suggests, polyurethane sealants contain polyurethane resins, acrylic, and other types of solvents. They come in various finishes, from high gloss to soft sheen. They are commonly used on light-toned wood because they don’t cause yellowing.

The sealants could be oil-based or water-based. Oil-based polyurethane sealants offer the most durability but can be difficult to clean up (requires turpentine or mineral spirits). Water-based polyurethane, on the other hand, can be easily removed with water and soap.

Varnish

Varnish is a blend of resin, drying oil and solvent. It doesn’t cause yellowing, just like polyurethane. For outdoor wood, you will need marine varnish, which provides protection from water and sun damage. For indoor wood furniture, spar varnish is usually recommended. To clean up the varnish, you will also need mineral spirits or turpentine.

Lacquer

Lacquer is typically made by dissolving synthetic or tree resin in alcohol. It tends to form a yellowish tint over time, making it unappealing on lighter wood. However, on deep-toned wood, it leaves behind a rich, warm, hard-shell finish.

Here’s how to waterproof outdoor wood pieces with a sealant.

  1. Prep the wood by sanding down the surface to remove any imperfections or previous coating. You can do this with a rough sandpaper.
  2. Next, even out the surface with another (finer) sandpaper. Then, wipe off the sanding residues on the surface.
  3. Choose a marine sealant and apply it evenly on the wood surface with a brush or sprayer. Give it 4-10 hours to dry according to the product instructions.
  4. Some sealants may require another light sanding before you apply the next coat. In this case, sand down the furniture again with a finer grit paper or steel wool. Then, wipe off the dust with a dry clean cloth.
  5. Now, apply the second coat and allow it to dry completely. You can sand the furniture again and apply another coat and so on until you get the desired finish. When you’re done, we recommend allowing the wood piece to cure for at least 3 days before using it again.

NOTE: Unlike natural oils, don’t shake or stir sealants before using them, as this can cause air bubbles on the wood surface.

METHOD THREE: Using Stain-sealant Combo

If you have a large project to waterproof and don’t have a lot of time to spare, you can use a quality stain-sealant combo (or an all-in-one stain and polyurethane sealer). As the name suggests, a stain-sealant combo adds color to your project while simultaneously providing water protection, usually with two easy coats. They are typically made of color pigments and binders and can be alkyd-based, water-based, or oil-based. Also, the amount of pigment in the mixture determines whether the finish will be opaque, transparent, or translucent. So, you will find the product in different tints and shine values.

The main advantage of using a stain-sealer combo is that it doesn’t cause yellowing or darken your wood over time. However, it does contain VOCs. You will need to reapply it annually or after every two years, depending on where you use the furniture.

How to waterproof outdoor wood with a stain-sealer

  1. For weathered wood pieces or those with an old finish, start by sanding it with an 80 grit sandpaper or a 5″/6″ orbital sander.
  2. Then scrub it clean using a stiff-bristled brush dipped in a cleaning formula (four parts water plus one part deck cleaner)
  3. Rinse off the cleaner and allow the furniture to dry completely
  4. For bare wood or new unfinished furniture, you can apply a thin coat of the stain-sealer at once using a bristle paintbrush.
  5. Give the piece until the next day to dry.
  6. Then apply another coat of stain-sealer, working it into every corner and slats in the furniture.
  7. Give it the next 24 hours or more to dry before using it.

NOTE: Make sure you have your respirator on while working with a stain sealer. Also, the work area should be well-ventilated. When done, you can clean up the paintbrush using mineral spirits.

How to Waterproof Painted Wood Furniture for Outdoors?

There are two main solutions available for waterproofing painted wood – you can use a wood sealant, or you can use natural oil.

Using Natural Oil

Natural oil products like tung, linseed, or walnut oil can be used to waterproof painted wood. The good thing about these products is that they are all effective and readily available. However, their prices vary, with walnut and linseed being cheaper while tung oil is more expensive. Because of the price difference, it is more common to use walnut or linseed oil for large projects while tung oil is used for small projects. You can obtain each of the products from a grocery or hardware store.

Step-by-step Instructions for Using Natural Oil

Prepare the Table

Start by removing any imperfections on the wood surface. This involves sanding down any markings, loose bits, and blemishes. Start with a rough (thick) sandpaper, then scrape it again with a fine-grit sandpaper. This will renew the wood seam and prepare it for absorption. Next, wipe down the dust from the wood surface.

Prepare the Oil

Once the furniture is ready, prepare the oil mixture you want to use. Mix one part of the oil (Tung oil, walnut oil, or linseed oil), one part turpentine, and one-half part apple cider vinegar. Shake very well!

Preparing the oil this way provides a more durable finish for the wood.

Apply the First Coat

Now, layer the first coat of the mixture on the wood surface. Use a dry cloth for this. Some people might pour the oil directly on the wood piece and then proceed to spread it with a paintbrush. But we don’t recommend this as it can create puddles on the wood and cause the oil not to be evenly distributed. In worse cases, it could lead to discoloration. So, the best plan is to use a dry cloth; put a bit of oil on it, then work it on the wood till it dries. Then add more oil. Make sure you’re wearing your hand gloves.

Allow it to Dry

Allow the wood piece to dry for at least half an hour. Then, remove excess oil with a clean cloth. After that, allow the wood to absorb the mixture well. Leave it to dry for 1-2 days (or more), depending on the weather. When it’s fully dry, scrape the surface with steel wool and wipe with a dry cloth to prepare it for the second coat.

Apply the Final Coat

Now, apply a second coat just like you applied the first. Allow it to dry for a day or two, and then sand with steel wool.

You may need to apply a third or fourth coat depending on the condition of the furniture and how well it absorbs the oil mixture. Altogether, the entire process might take several days or even weeks, but once you’re done, the wood piece should stay waterproof for a long time.

Using a Wood Sealant

Using sealant is arguably the best way to waterproof painted wood furniture. It is also the most convenient and easiest. While you can expect a change in appearance, it’s usually beautiful and shiny.

Step-by-step Waterproofing Process With a Sealer

  1. Clean the painted wood: Start by cleaning the wood furniture. Prepare a cleaning solution by mixing one gallon of water with a quarter of liquid detergent. Mix well in a bucket. Now dip your cleaning brush into the mixture and use it to scrub the painted wood surface thoroughly.
  2. Rinse and dry: Next, hose down the furniture with clean water and allow it to dry (might take up to 3 hours).
  3. Apply primer: Once the wood surface is dry (with the paint stripped), apply primer evenly with a brush. Doing this will make the sealer to last longer.
  4. Apply sealant: Now, apply a good sealant (polyurethane or varnish) evenly on the wood using a paintbrush. Then leave it to dry. This might take a day or two.

NOTE: By all means, try to work outdoors whether you’re using sealant or oil.

https://www.youtube.com/watch?v=65TDjszudVA=16s

What types of furniture can be used outdoors?

It is not news that some woods take longer to decay than others. So, it’s very important to choose wisely when picking wood for outdoor use. In other words, before putting out your money for any patio or garden furniture, you must check the type of wood it’s made from. Although you may end up spending more money initially on a high-quality piece, it will pay off in the long run as you get more years of use from it.

Having said that, the market is filled with numerous kinds of natural wood; however, only a handful have proven to be formidable and durable when used outdoors. They are listed below:

  • Acacia
  • Cypress
  • Cedar
  • Black locust
  • Redwood
  • Rosewood
  • Satin
  • Sal
  • Teak wood (very expensive)
  • Ipe
  • Mahogany
  • Eucalyptus
  • Shorea
  • White Oak

Other Methods to Make sure your outdoor furniture lasts longer

Besides sealing wood, there are other ways to make it last longer.

Change the Location

If you have your wooden furniture in an area where it’s constantly exposed to extreme weather conditions such as sunlight and high humidity, you could move it to a new location that doesn’t get as much weather exposure. This is the best route to take if you have a lot of garden space or areas to keep your outdoor furniture. Ideally, you want to keep them somewhere that provides shade from direct sunlight, such as a pergola.

Move furniture indoors

Even when you’ve sealed wooden furniture, it’s still recommended to take them indoors during harsh seasons like winter. Many sealants and finishes can’t withstand the freezing temperatures in winter for long. So, it’s best to move the furniture indoors until the next dry season. Doing this will greatly prolong the lifespan of your furniture.

Use a furniture cover.

Lastly, you can invest in a heavy-duty outdoor furniture cover. This is often the route most people take, especially when they have heavy furnishings. You can cover outdoor furniture during winter or when you don’t plan on using them for a long time. Doing this protects the furniture from moisture, UV rays, and other bad weather conditions.

Regular cleaning

Cleaning outdoor furniture regularly is another way to make sure they last longer. Things like mold, mildew, and dirt can easily cause wood to deteriorate. Cleaning helps to prevent these things from accumulating on the wood surface.

Frequently Asked Questions

What can I use to protect wood furniture outside?

There are various things you can use to protect wooden furniture. The most common ones are natural oils and sealants. You can also use an outdoor furniture cover.

What’s the best way to protect wood furniture from UV radiation?

All the methods we discussed above are sufficient for protecting wood furniture from harmful UV rays. However, we recommend using linseed or Tung oil on stained outdoor furniture and water-based -polyurethane or -lacquer on indoor furniture.

How do you seal wood without it getting darker?

The best way to seal wood without altering the color is to coat it with a water-based sealant. This could be polyurethane or acrylic lacquer. Both products will give the wood a shiny finish without making it darker. Oil-based sealers, on the other hand, will cause yellowing in pine and darken other types of wood. The same outcome (yellowing) is recorded when using linseed or other natural oils.

How often should I oil wood furniture?

This depends on how protected the wood furniture is. If the furniture is used indoors or in an enclosed area outdoors (such as a pergola), you should oil it yearly. However, if they’re used outside where they’re exposed to the elements, it’s best to oil them at least twice per year. The gist is to apply a new coat of oil whenever the wood starts looking dry; this helps preserve its water-resistance and keep it in a pristine condition.

Does Paint Protect Wood Outdoors?

Yes. Applying paint over wood helps protect it from outdoor elements by making it waterproof and able to withstand cold and hot temperatures. When applying paint to outdoor wood furniture, make sure it’s exterior paint rated for outdoor use. Also, it’s advisable to apply a coat of primer before the paint.