How To Build A Wood Planter Box

A wooden planter box is more than just a container for your favorite plants; it is also a fashionable and customisable piece that can be used to give elegance to any garden, patio, or balcony the homeowner may have. Constructing a wooden planter box is a gratifying way to demonstrate your creative abilities and green thumb, regardless of whether you are an experienced do-it-yourself enthusiast or a novice seeking for a straightforward project. In this post, we will walk you through the process of making your very own planter box, beginning with the selection of the ideal wood and continuing through the assembly and finishing of the box. Congratulations!

Your dreams of gardening are about to come true, so get ready to roll up your sleeves and get started!
For the purpose of lining a wooden planter box, you may make use of materials like as plastic sheeting, landscape fabric, or liners that are waterproof. To fit the interior of the planter box, just cut the lining material to the appropriate dimensions, making sure that it covers the bottom and sides, and then trim away any excess. In this way, the soil is prevented from coming into direct touch with the wood, which in turn serves to extend the life of the planter box.

How To Build A Planter Box For Vegetables

Item	Description
Pressure-treated timber	Dimensions: 5cm x 5cm Quantities: 9 lengths of 1m 7 lengths of 60cm 23 lengths of 40cm 1 length of 45cm
Gravel board	Dimensions: 15cm x 1cm Length: 3.45m
Tools	Saw Drill 3mm wood drill bit Screwdriver Try square Pencil Tape measure
Zinc-plated screws	75 x 7.5cm screws 20 x 5cm screws
Total time	A weekend
Step 1: Preparation	Mark and cut all timber pieces to the specified lengths. Ensure cuts are square for a smooth finish. Use a 3mm drill bit to create holes about 2.5cm from the ends of each timber length.
Step 2: Frame Layout	Lay out two 100cm, 60cm, and 40cm lengths to form the planner frame. Ensure drilled holes are on the same side. Check angles with a try square and fix with 7.5cm screws.
Step 3: Bottom Board Installation	Cut treated gravel boards for the planter bottom. Place the bottom boards on the frame, allowing for gaps up to 5cm. Pre-drill and check the frame square before attaching with 5cm screws.
Step 4: Overturning the Frame	Flip the frame so the bottom boards are on the ground. Lay the next course with alternating corner joins. Ensure ends are flush and secure with 7.5cm screws.
Step 5: Building Up Edges	Build up four layers by repeating the previous steps. Instead of a final 60cm piece, use a 100cm length across the gap for support.
Step 6: Crossbar Cutting	Measure and cut the crossbar piece in place for a perfect fit.
Step 7: Attaching Crossbar Pieces	Attach one end of the crossbar with a 7.5cm screw from above. Screw in the other end from the outside of the frame.
Step 8: Laying Additional Pieces	Place the 45cm length across the other gap, aligning it with the adjacent side. Check angles and secure into place.
Step 9: Finalizing Timber Courses	Finish with two 40cm lengths at right angles to the 45cm piece. Cut the final length to fit the remaining gap. Continue adding 40cm lengths with alternating joints until four layers are achieved.

Why Should You Construct Your Own Grow Box?

If you are wanting to incorporate some high-quality and visually appealing outdoor planters into your porch or patio, you will rapidly find yourself in a state of confusion due to the abundance of options available at the hardware store. On top of that, you can end up spending quite an amount of money for only one, and obviously, you will spend considerably more money if you require two or three!

I am very interested in constructing this do-it-yourself wooden planter box!
What’s the answer? Try your hand at it! The layout is quite straightforward, and it does not call for a great deal of labor on your part. Spend a half an hour on the construction, then spend some time obtaining the necessary resources. This project is ideal for you if you have a limited amount of space that you need to fill.

🌲 Choose the Right Wood

• Best choices: cedar, redwood, teak, pressure-treated wood—naturally rot-resistant
• Softer woods need more waterproofing protection.

💧 Seal the Wood Interior

• Sealant options: polyurethane, marine varnish, tung oil.
• Application:
  1. Sand the interior.
  2. Brush on two coats, covering every surface (include bottom and edges!).
  3. Let it cure at least 24 hours before adding soil.

🧰 Add a Waterproof Liner

• Options: plastic/pond liner, landscaping fabric, thick garbage bags, pond liner .
• Tips:
  • Fit it snugly, fold over edges for coverage.
  • Poke drainage holes.
  • Staple or glue plastic liner to keep it in place (tiny staples near top won’t leak) .

➕ Install Proper Drainage

• Drill holes in the bottom.
• Layer rocks, pebbles, or landscaping fabric to stop soil clogging.
• Elevate the planter slightly (bricks/blocks) for airflow and water escape.

🛡️ Use Waterproof Membrane for Extra Protection

• Liquid rubber or bitumen membranes create a seamless, durable inner coat .
• Benefits:
  • Flexes with wood; prevents leaks at seams and screws.
  • Plant-safe once cured
  • Apply 2–4 coats, focus on corners and drainage hole rims.

🧶 Optional: Epoxy or Resin Coat

• Redditors suggest epoxy for a glossy, durable barrier—but it can hide wood movement joints and requires care in drainage .

🛠️ Quick Comparison Table

Method	Pros	Cons
Sealant only	Easy, keeps wood looking natural	Might fail if liner leaks or wears
Plastic/pond liner	Simple, effective moisture barrier	Needs precise fitting and drainage holes
Liquid membrane	Seamless, flexible, plant-safe	More costly, requires dry prep and curing time
Epoxy/resin	Very durable	Can trap moisture, may crack with wood movement

🧵 Reddit Wisdom

“Stapling a plastic liner inside is probably the most effective, simple method.”

✅ Final Recommendations

1. Use rot-resistant wood (cedar, redwood).
2. Seal interior with oil/varnish for first barrier.
3. Line inside with plastic or pond liner, staple near top, add drainage holes.
4. Boost with liquid waterproof membrane—focus on seams and holes.
5. Ensure good drainage (drill holes + gravel + elevation).
6. Optional: epoxy for maximum protection if lined correctly.

🎥 Want a visual walkthrough?

Here’s a helpful video:

Why It Is Important to Consider Protecting the Interior of a Wooden Planter
As a result of its inherently porous nature, wood is sensitive to the absorption of water, the formation of mould, and eventually breakdown. Those who do not properly waterproof their wooden planters are at risk of:

1. Take in an excessive amount of moisture, which will eventually cause decay.
2. As a result of water damage, cracks and warping manifest themselves.
3. mould and mildew, harming plant health.
4. Deteriorate rapidly, hence shortening their longevity time. It is possible to ensure that your planter will continue to be in excellent condition for many years by employing waterproofing measures.

(Shows sealing and liner steps clearly.)

✨ Summary

Combining sealant, liner, and a waterproof membrane gives your planter the best defense—ensuring it lasts, breathes, and supports healthy plants.