How To Waterproof Wood Furniture For Outdoors: 5 Methods

Summer is just around the corner and with it comes the perfect time to spend our days (and nights!) outside.

The thing is, wooden outdoor furniture -such as chairs and tables- needs protection from the elements otherwise it won’t last long.

Below are 5 of the most effective methods to waterproof and protect your outdoor furniture.

1. Use Varnish

Varnish is a mixture of solvent, drying oil, and resin that produces a hard scratch-resistant finish. It’s flexible, doesn’t turn yellow, and doesn’t crack under stress.

Marine varnish offers excellent protection against moisture and UV rays.

The downside to applying varnish is that it takes a lot longer than other clear coat sealants.

Here’s how to apply varnish effectively:

1. Start here if your wood furniture is old: sand the furniture using 80 grit sandpaper coupled with a 6-inch orbital sander (5-inch is also good).
2. Use a rough brush to scrub the furniture with deck cleaner and water mixture (ratio 1:4).
3. Wash the cleaning mixture off the furniture then allow it to dry completely.
4. Start here if your furniture is new or without a finish: apply a thin layer of varnish using a natural bristle paintbrush, making sure you coat between the slats and cover the crevices.
5. Let the furniture dry completely (overnight should be enough).
6. Apply another thin coat of varnish and let it dry completely before you apply the next layer. Do this up to 8 coats.
7. After applying the last coat, let the furniture dry for at least a full day.

You’ll probably need to reapply varnish every 2 or 3 years. Here are some tips to ensure the best results:

• Apply varnish at room temperature to support proper adhesion and drying.
• Don’t vigorously stir or shake varnish before application to prevent the formation of air bubbles on the surface of the coat. These bubbles stay visible even after varnish dries

2. Use Polyurethane

Polyurethane is basically plastic in liquid form.

Once it dries, it creates a scratch-resistant and dent-resistant finish that’s also impenetrable by water.

Polyurethane sealants can be water-based or oil-based polyurethanes are available, so you need to make sure you’re using an oil-based variety before applying it to your outdoor wood furniture, otherwise, it won’t be waterproof.

The finish of an oil-based polyurethane looks similar to varnish but is less time-consuming to achieve as it requires only 2 coats, not 8 like varnish.

On the downside, you should be more careful while applying polyurethane because it contains more volatile organic compounds that can cause irritation and health issues.

Here’s how to apply polyurethane effectively:

1. If your wood furniture is old or has another finish, follow steps 1 to 3 in the varnish section then come back here. If your furniture is new or lacks a finish, go right ahead.
2. Apply a thin layer of polyurethane using a natural bristle paintbrush.
3. Make sure you coat between the slats and cover any crevices or gaps.
4. Let the furniture dry completely (overnight should be enough).
5. Apply another thin coat of polyurethane and let it dry for at least a full day.

Polyurethane lasts around 5 to 8 years before it requires reapplication. Here are some tips to ensure the best results:

• Apply polyurethane at room temperature.
• Provide good ventilation.
• Don’t vigorously stir or shake polyurethane before application to prevent air bubbles.

3. Use Lacquer

Lacquer is resin (synthetic or tree) dissolved in an alcohol vehicle. It’s thinner than both varnish and polyurethane, so it has deeper penetration and a higher level of protection.

Lacquer gives a scratch-resistant finish with a warm tinge that looks great on wood (especially darker varieties).

It also dries faster than other sealants, so application is less time-consuming.

Lacquer is available in multiple sheen options and is very durable, easily lasting more than 10 or 15 years with proper use.

On the downside, it contains high levels of volatile organic compounds.

Here’s how to apply lacquer effectively:

1. If your wood furniture is old or has another finish, follow steps 1 to 3 in the varnish section then come back here. If your furniture is new or lacks a finish, go right ahead.
2. Apply a thin layer of lacquer using a natural bristle paintbrush. Make sure you coat between the slats and cover any crevices or grooves.
3. Let the furniture dry completely for about 2 hours.
4. Apply another thin coat of lacquer and let it dry for another 2 hours.

Lacquer lasts longer than both varnish and polyurethane, so it can take at least a decade before you need to reapply. Here are some tips to ensure the best results:

• Apply lacquer at room temperature.
• Work in good ventilation.
• Don’t vigorously stir or shake lacquer before application.

4. Use Stained Sealant

Using a stained sealant is an excellent way to color and waterproof your wood furniture when you’re short on time.

In the same process, the stain will add a rich pigment to the wood while the sealant provides a layer of protection.

Typically the sealant in these products is polyurethane.

As for the stain, it can vary in the concentration of pigment and shine value to give you a range of finishes from transparent and flat to glossy opaque.

On the downside, stained sealants also contain volatile organic compounds.

Here’s how to apply stained sealants effectively:

1. If your wood furniture is old or has another finish, follow steps 1 to 3 in the varnish section then come back here. If your furniture is new or lacks a finish, go right ahead.
2. Apply a thin layer of the stained sealant using a natural bristle paintbrush. Make sure you coat between the slats and cover any grooves.
3. Let the furniture dry completely for at least 8 hours.
4. Apply another thin coat of stained sealant and let it dry for at least a full day before using the furniture.

Stained sealants last around 5 to 10 years before they require reapplication. Here are some tips to ensure the best results:

• Apply the product at room temperature.
• Work somewhere with adequate ventilation.
• Don’t vigorously stir or shake the product before application.

5. Use Natural Oils

The easiest and safest way to waterproof furniture for outdoor use is to use natural oils.

Unlike the sealants we discussed above, they’re free of volatile organic compounds so you won’t have to worry about toxicity.

The only issue with natural oils is that they provide a lower level of protection than varnish, polyurethane, or lacquer.

This means you’re looking at moderate waterproofing that’s more suitable for wood furniture in sheltered locations.

Examples of natural oils you can apply on wood include linseed oil (raw or polymerized) or tung oil.

These have been used for centuries to protect and waterproof wood.

These are the types used in most hand-rubbed oil finishes.

Here’s how to apply natural oils effectively:

1. If your wood furniture is old or has another finish, follow steps 1 to 3 in the varnish section then come back here. If your furniture is new or lacks a finish, go right ahead.
2. Apply a thin layer of oil using a natural bristle paintbrush. Make sure you coat between the slats and cover any grooves.
3. Check that the wood is saturated then wipe the excess oil with a clean rag. Rub well to remove any residual oil.
4. Let the furniture dry completely for at least 8 hours.
5. Repeat for as many coats as you want then wait for a full day before using the furniture to ensure thorough drying.

Natural oils aren’t as durable as other sealants, they may require reapplication every 6 months to 1 year. 

An important tip to keep in mind is to dunk the used rags in water immediately after rubbing the oil and the rag becoming saturated.

This is to avoid the spontaneous combustion of rags once the oil starts to dry.

How To Waterproof Painted Wood Furniture For Outdoors

Waterproofing painted wood furniture for outdoors is a simple process that resembles the steps we explained above. Here’s how you can do it:

1. Clean the Wood

Use a rough brush to scrub the furniture with liquid detergent and water mixture (ratio 1:4). 

2. Give It Time to Dry

Then, wash the cleaning mixture off the furniture and let it dry completely for a few hours.

3. Apply Your Sealant of Choice

Before applying your sealant of choice, don’t forget to apply a layer of primer to improve the durability of the sealant.

As for the type of sealant you should use, it’s best to go with either polyurethane or varnish for sealing painted wood. Use a natural bristle paintbrush.

4. Leave to Dry

Finally, allow the painted wood furniture to dry thoroughly for at least 24 hours before using it.