Build a Raised Garden Bed from Formwork Boards

Why build a raised garden bed from formwork boards?

Formwork boards are industrially manufactured panels made from pressure-treated softwood. They are designed for demanding use on construction sites, and that durability makes them ideal for the garden.

The material withstands pressure and the elements. Its standard thickness of 19 to 27 millimetres provides stability where thinner garden lumber can give way. It helps prevent the boards from bowing under the weight of the soil.

The price per square metre is often lower than that of traditional garden lumber. You get hardware-store quality at industrial prices. Their long service life makes them a worthwhile investment for years to come.

What materials and tools do you need?

The materials list is manageable and focuses on the essentials.

Materials for your formwork-board raised bed

• Formwork boards: 12 pieces (e.g. 200 cm x 20 cm x 2,7 cm) for a bed measuring 200 cm long, 100 cm wide and 80 cm high.
• Corner brackets: 8 heavy-duty galvanized brackets (e.g. 80 mm x 80 mm).
• Screws: Stainless steel screws (4,0 x 60 mm and 4,0 x 40 mm). Stainless steel won't rust in the soil.
• Dimpled membrane: Enough to line the entire inside of the bed. It protects the wood from constant moisture.
• Wire mesh: One piece of hardware cloth to protect the base from voles.
• Filling materials: Coarse yard waste, leaves, compost and garden soil.

A material stand or rolling base makes it much easier to transport the heavy panels and materials.

Tools for safe construction

Your hands are your most important tools. Protect them with sturdy work gloves. The

Leather work gloves, size 8, sturdy gloves

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For tougher cuts or longer jobs, choose the thicker

Leather work gloves, size 10, sturdy gloves

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Mechanic's work gloves XL/10, sturdy workshop gloves

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You will also need a cordless screwdriver, jigsaw, clamps, level, tape measure and pencil. Wear hearing protection when using the saw.

The choice of lumber determines how long the bed lasts. Pressure-treated formwork boards are an affordable, durable alternative to expensive hardwoods. You won't have to compromise on stability.

How do you build a raised garden bed step by step?

The construction follows a simple principle: a sturdy frame made from four walls.

Step 1: Cut and prepare the formwork boards

Plan the dimensions. A classic size is 200 cm long, 100 cm wide and 80 cm high. This gives you a spacious bed that's easy on your back.

Cut the wall sections from the long formwork boards. For our example, cut four pieces measuring 200 cm (long sides), four pieces measuring 100 cm (end sides) and four pieces measuring 80 cm (for the second layer).

Sand the cut edges smooth. This prevents splintering and makes the boards safer to handle.

Step 2: Screw the frame together

Start with the bottom layer. Arrange two long panels and two short panels into a rectangle. The corners should meet at precise 90-degree angles.

Secure each corner with two galvanized brackets. From the outside, drive the 60-mm stainless steel screws through the bracket holes and into the wood. The longer screws provide a secure hold in the thick formwork boards.

Repeat the process for the second layer. Place it on top of the lower layer, offset like a log-cabin wall. This adds stability. Screw the layers together at the corners using the 40-mm screws.

After assembly, check that each corner is square with a level. A crooked frame is difficult to fix later.

Step 3: Line the inside and protect the base

Protect the inside of the bed. Measure the four walls and the base, then cut the dimpled membrane to size.

Staple or nail the membrane to the wooden box, starting at the top. The dimples should face the wood to create an air gap that lets moisture drain away.

First, lay wire mesh across the base to keep rodents out. Place the dimpled membrane over it. Make several holes in the membrane at the base so water can drain. Standing water can damage the roots.

Store leftover materials, such as membrane scraps or wood waste, in practical baskets made from durable materials. This helps keep your work area tidy.

Where should you place and how should you fill the raised bed?

The location can make all the difference to your gardening success. Choose a sunny, level spot. Easy access from all sides makes maintenance much simpler.

Remove the turf from the area. A little leveling is all you need. The raised bed sits directly on the soil, with hardware cloth underneath to keep voles out.

The classic layered filling method in detail

Fill the bed using the "decomposing core" method, working from coarse to fine materials.

1. Drainage layer (approx. 25 cm): Coarse wood chips, thin branches and hedge clippings. This layer provides ventilation and helps water drain.
2. Structural material (approx. 15 cm): Upside-down turf, leaves and unfinished compost. This layer starts to decompose and generates heat.
3. Fine compost (approx. 20 cm): Partially matured compost or manure. It provides nutrients for your plants over the medium term.
4. Planting layer (approx. 20 cm): A mixture of mature compost and high-quality garden soil. Plant young plants or sow seeds in this layer.

Lightly tamp down each layer with your feet. Fill the bed to around five centimeters below the rim. This leaves room for mulch and watering.

The heat generated as the material decomposes inside the bed gives your plants a head start and helps you harvest earlier. It extends the growing season by weeks in spring and again in fall. That more than makes up for the extra effort involved in filling the bed.

How do you maintain and plant your raised bed?

A raised bed made from formwork boards is a dynamic system. During the first year, the soil settles by 10 to 20 centimeters as the contents decompose. Simply top it up with mature compost the following year.

The right planting plan for every season

Start with heavy feeders in the first year. They make the most of the high nutrient content. Plant tomatoes, zucchini, cabbage or celery.

In the second year, grow medium feeders such as lettuce, spinach, carrots or onions. In the third year, plant light feeders such as beans, peas or herbs.

Then replace the top two layers completely to replenish the nutrients. Compost the old material so you can use it later.

For creative gardening projects with kids, find inspiration in wooden animals and figures or classic wooden toys, which can also be used as decorations.

Long-term care for the wood and soil

Check the corner connectors for stability in spring. Tighten any loose screws. It only takes five minutes.

Before winter, you can cover the empty bed with a tarp. This protects the soil from washing away. A wood cover tarp is perfect for the job.

Check the dimpled membrane inside the bed every five years. Replace any damaged sections to keep the wood at the core dry.

With this care, your raised bed made from formwork boards will last for more than a decade. Every year, it provides a fresh harvest at a comfortable working height. Building one is well worth it.

Frequently asked questions

What are the benefits of a raised bed made from formwork boards?

Formwork boards are extremely durable, weather-resistant and cost-effective. The thick wooden panels provide excellent insulation for the bed contents, which speeds up plant growth. Their standard dimensions make them easier to cut, while the sturdy construction helps prevent bowing and ensures a long service life.

Do formwork boards need any special treatment?

Buy pressure-treated formwork boards for outdoor use. They are already protected against weather and rot. Avoid using chemical treatments inside the bed so your plants are not exposed to them. Line the inside with a dimpled membrane.

What tools do I need to build it?

You need a jigsaw or circular saw for cutting, a cordless screwdriver, a level, a tape measure and a clamp. Sturdy work gloves such as PRODUCT_25425 are essential to protect your hands. A workshop trolley is useful for transporting and laying out materials.

How do I fill a raised bed made from formwork boards correctly?

Start with a coarse drainage layer made from branches or wood chips. Add upside-down turf or leaves, followed by coarse compost, and finish with a top layer of mature compost mixed with high-quality garden soil. This layered filling generates heat as it decomposes and provides nutrients.

How long does a raised bed made from formwork boards last?

With pressure-treated formwork boards and a dimpled membrane to prevent direct contact with the soil, a raised bed like this will last 10 to 15 years. You can extend its service life by protecting it from moisture with a wood cover tarp in winter.