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5 Steps on How to Waterproof the Inside of a Wood Planter Box!

If you have a deep interest in tending to plant life and enhancing your outdoor areas with organic beauty, then you likely recognize the significance of a finely crafted wood planter box for your indoor plants.

Wooden planter boxes contribute a touch of old-world allure and sophistication to any garden or patio scene.

However, to guarantee their endurance, it’s vital to address a common issue.

It is important to waterproof a wooden planter box!

In this post, we will explore how to waterproof the inside of a wood planter box, enabling it to stand strong against different weather elements while creating a nurturing habitat for your cherished flora.

Whether you possess ample gardening experience or are a newcomer seeking to enhance your surroundings, our guidance will assist you in waterproofing your wood planter box and making an impressive and eco-friendly potted garden that will thrive throughout multiple seasons.

Let’s begin!

How to Waterproof the Inside of a Wood Planter Box
Image via Pixabay

How to Waterproof the Inside of a Wood Planter Box?

Here are the steps to waterproof the inside of a wood planter box:

1.   Choose the Right Sealant for Your Planter Box

When it comes to preserving the inner lining of a wooden planter box from water damage, the most crucial phase involves selecting the most suitable protective substance.

Given the multitude of options available, it becomes imperative to opt for a specific solution designed exclusively for wood and outdoor applications.

The preferred sealants should provide comprehensive protection to your planter against water, UV rays, and the development of mold. Prominent choices such as polyurethane, linseed oil, and marine-grade varnishes are renowned for their robustness and water-sealant attributes.

The ideal option will vary depending on the selected woods for planter boxes.

It’s also advisable to select products that dry properly, are environmentally friendly, and are safe for plants, considering their direct contact with the soil and roots.

By making an appropriate selection, you will waterproof the inside of your wooden planter box correctly and establish a strong foundation for a successful preservation process, ensuring that the inner lining of your wood planter box doesn’t get wet throughout all seasons.

2.   Prepare the Wood Planter Box

Prior to waterproofing your wooden planter using the protective sealant, it’s crucial to prepare your wooden planter box to achieve optimal effectiveness and endurance.

  • Commence by meticulously cleaning both the inside walls and the exterior of your wooden planter boxes.

  • Employ a firm brush or sandpaper to remove the remnants of prior paint or excess varnish. Then, use clean cloth to remove any dirt. This measure not only enhances the adhesion of the sealant but also prevents any pre-existing mold or mildew from being trapped beneath the waterproof layer.

  • Next, carefully inspect the wooden planter box for any cracks, fissures, or openings in the wood. Address these imperfections by sealing them with wood filler or putty, as they may compromise the waterproofing process. Allow the filler to thoroughly dry and subsequently sand the surface until it attains a smooth and even texture.

  • To preclude water from seeping into the lower section of the wood planter boxes, establish appropriate drainage hole apertures. These holes will facilitate the escape of excess water, thwarting waterlogging that could prove detrimental to the plant roots. Drill holes, evenly dispersed across the bottom of the box, ensuring that the drainage hole apertures are sufficient to enable proper water flow.

With all that done, you are now ready to move to the next step.

3.   Apply Waterproof Product to Your Wood Planter

Following the selection of the appropriate protective substance and preparation of the wooden planter box, it is now time to administer the waterproof product using the most effective method.

  • Ensure that you are working in a well-ventilated area to avoid inhaling any fumes emitted by the sealant.

  • In the case of a brush-on sealant, commence by dipping the brush into the product and uniformly applying it to the interior of the planter boxes. Employ smooth and even strokes, adhering to the direction of the wood grain. Guarantee comprehensive coverage, including all corners and edges, establishing a robust barrier against moisture. If you want to apply a second coat, allow the first seal to dry completely.

  • For spray-on sealants, hold the can at a consistent distance from the wood surface and employ a back-and-forth motion while spraying. Exercise caution to avoid oversaturation, preventing any drips or puddles. If necessary, apply thin additional coats instead of a single wet, heavy one, as this yields superior results.

  • When utilizing oil-based sealants, allow the initial coat to dry completely before adding more coats to further protect the wood planter. Water-based sealants typically dry faster, but follow the manufacturer’s guidelines for the recommended drying time between applications.

Replicate the application process for the outer surface, ensuring the entire box is well protected.

4.   Allow Drying and Curing

Following the application of the water-resistant substance to both the interior and exterior of the planter box, the pivotal phase of allowing adequate drying and curing commences.

“Drying refers to the process wherein the solvent or water content within the sealant evaporates, leaving behind a safeguarding film on the exposed wood surface.”

This typically takes a few hours to a day, contingent on the sealant type and prevailing environmental conditions. Excess varnish takes longer to dry thoroughly.

Throughout the drying period, it’s essential to maintain the planter box in a well-ventilated area, shielded from direct sunlight and rain. Adequate ventilation facilitates the dispersion of fumes and helps avert the development of bubbles or uneven drying.

Opting for a covered location or a garage can prove ideal for safeguarding the planters from outdoor elements during this stage.

Curing entails the comprehensive chemical hardening and bonding of the sealant to the wood planter, ensuring its efficacy in repelling moisture and furnishing long-term protection. Curing times can significantly vary based on the sealant type and the manufacturer’s recommendations.

How to Waterproof the Inside of a Wood Planter Box 1
Image via Pexles

5.   Test for Waterproof Wooden Planter Box

To execute the test, prepare a bucket or container with water and submerge the wooden planter box inside, ensuring complete immersion.

Allow it to rest in the water for several hours, ideally overnight.

During this waiting period, inspect the exterior of the planter box for any indications of moisture or water seepage. Focus your attention on seams, corners, and edges of wood planters only, as these are common areas prone to water penetration.

Remove the planter box from the water and dry the exterior using a towel. Examine the interior of the box for any water leakage or moisture. Should you observe any water ingress or signs of moisture on the exterior, it might signify an insufficient seal or a spot that requires further attention.

In the event of encountering any leaks or unsatisfactory outcomes, consider reapplying the waterproofing seal product to cover the affected areas or applying an additional coat to protect and fortify the seal. Ensure you allocate sufficient time for drying and curing any touch-ups you undertake.

Alternatively, if the planter box successfully passes the waterproofing test, congratulations are in order!

You have effectively established a water-resistant barrier that will protect your plants and wooden box for an extended duration.


Once you master the skill to waterproof a wooden planter box, you will have indispensable wooden planter like any gardening enthusiast aiming to cultivate a sustainable and flourishing container garden.

With dutiful maintenance and attentiveness, your waterproofed wood planter boxes will serve as a testament to your unwavering commitment to nurturing nature’s splendor in your outdoor spaces.

Roll up your sleeves, embark on this gratifying expedition, and witness plants in your wooden planter box prosper and blossom, as you craft an oasis of greenery that imparts delight and serenity to your surroundings.