Building Raised Garden Beds with Concrete Blocks

Raised garden beds make growing vegetables flowers herbs, and other plants easy and convenient. The elevated structure reduces back strain from bending, improves drainage, and allows control over the soil quality. Concrete blocks are a smart, durable material for constructing raised beds in your backyard, patio, or balcony.

Concrete block raised beds can last for decades with minimal upkeep. They are also fully customizable to any garden size or shape. Follow this guide to learn how concrete blocks work for raised beds tips for construction, and care for garden beds built from these hardy modular bricks.

Why Use Concrete Blocks for Raised Beds?

Concrete masonry units, also called CMUs or concrete blocks, are great for building raised garden beds. Here are some of the top advantages of concrete blocks:

  • Durability: If you build concrete block raised beds the right way, they will last at least 30 years. Concrete holds up well to weather, soil pressure, and seasonal freeze/thaw cycles.

  • Design That Can Be Changed: You can make raised beds of any length, width, or height by stacking concrete blocks. Beds up to 24 inches high can be built without mortar.

  • Good Weight and Stability – Weighing ~30 pounds each, concrete blocks resist shifting and stay neatly in place once laid and filled. Their weight also helps block weeds.

  • Heat Retention – The thermal mass of concrete helps soil stay warmer overnight in spring and fall, extending the growing season.

  • Affordable – Concrete blocks cost less than other raised bed building materials like brick, stone, or prefab kits.

  • Widely Available – Easy to find at home improvement stores and construction supply outlets.

Planning Your Concrete Block Raised Beds

Before building, draw up a plan for your raised bed dimensions and layout. Most standard 8 x 8 x 16 inch concrete blocks will form interior beds about 28-32 inches wide when laid on their sides. This provides a comfortable reach into the center from both sides.

Beds up to 4 feet wide still allow access from one side. For larger beds over 5 feet wide, allow access to the center by incorporating one or more side openings. Any length of bed can be created by adding more blocks.

Arrange multiple beds in a geometric pattern to maximize growing space. For example, a U-shape with three beds creates 50% more space than a single rectangular bed with the same number of blocks.

Plan for 18-24 inches of soil depth for most gardens. Shallower beds 10-12 inches work well for greens and herbs. For root crops like potatoes or carrots, make beds at least 16 inches deep.

Constructing Concrete Block Raised Beds

Step 1: Outline the footprint for your raised bed in your yard using stakes, paint, or chalk. Remove any grass or weeds. Level the soil surface, but don’t overly compact it.

Step 2: Make the bottom row level by digging shallow trenches or adding soil underneath as needed. Use a 2×4 and carpenter’s level across the tops of blocks for accuracy.

Step 3: Stack the second row of blocks, offsetting the blocks so the middle of each sits over the joint between blocks below. Insert 2-3 gravel rocks into each interior cavity for extra drainage.

Step 4: Check again for levelness as you build the bed upwards. Fill interior cavities with soil every 2-3 layers to stabilize the blocks.

Step 5: Leave the top row of blocks with interior cavities open for planting. Optionally face open cavities inwards or finish them off with wood or stone caps.

Step 6: Fill bed with good quality planting mix rich in organic matter. Amend native soil can also be used. Install drip irrigation if desired.

Step 7: Plant your raised bed! Seek crops suitable for your climate and season. Consider mixing flowers, herbs, and vegetables together or grouping compatible plants.

Caring for Concrete Block Raised Beds

Concrete block raised beds are pretty low maintenance. Follow these tips to keep them thriving for years:

  • Replenish mulch annually to retain moisture and nutrition. Organic options like wood chips, straw, and dried leaves work well.

  • Mix 1-2 inches of aged compost or well-rotted manure into the soil each spring. This replaces nutrients that plants consumed the previous season.

  • Pull any weeds promptly to prevent roots from taking hold. Avoid using herbicides which can leach into food crops.

  • Water beds 1-2 inches per week. Check soil moisture before watering and adjust as needed based on weather and plant types.

  • Make repairs immediately if any blocks crack, spall, or shift out of place over time. This will prevent further damage.

  • Expect some natural settling of soil over the first year. Top off beds with extra planting mix as needed.

  • In cold climates, add extra mulch around overwintering plants to protect roots from frost heave and freeze/thaw cycles which can shift blocks.

With smart construction and care, raised beds from concrete blocks can sustainably grow beautiful productive gardens for decades on end. Their durability provides gardeners with an abundance of planting space that only gets better with age. Let your imagination run wild designing the layout of your new concrete block raised bed garden!

Cinder Block Raised Bed


Are concrete blocks good for raised garden beds?

Build your raised bed with a decay-resistant type of wood, such as cedar, black cherry, oak (bur, chestnut, post, white), black locust, Osage orange, or redwood. (Source: USDA Forest Products Lab) Use a non-wood material such as stones, concrete blocks, bricks, or synthetic lumber.

What do I put on the bottom of a raised garden bed on concrete?

When setting up a raised garden bed on concrete, drainage and root health are key concerns. Start with a layer of landscape fabric to prevent soil from washing out. Above this, a layer of gravel or small stones can aid in drainage. Then, fill the bed with a mix of topsoil, compost, and other organic matter.

What is the difference between concrete blocks and cinder blocks?

Cinder blocks are hollow rectangle-shaped structures usually made of concrete and coal cinders which find use in construction sites. Concrete blocks often, on the other hand, are flattened constructs made of steel, wood or cement.

How to use cinder blocks for a raised garden bed?

A staircase pattern is a clever way to use cinder blocks for your raised garden bed. Simply stack the cinder blocks in a staircase pattern and use caps or wood planks to seal up the gaps. You can make each “step” a planter or spread them out. You can also place them next to actual stairs to create a matching wall. 5.

Should you build a garden bed with concrete blocks?

Creating a garden bed is an excellent way to enhance your outdoor space while enjoying the benefits of fresh produce and beautiful flowers. If you’re looking for a durable and affordable option, building a raised garden bed with concrete blocks might just be the perfect solution.

How much does a cinder block garden bed cost?

At just $2 to $3 per block, the most affordable way to build a raised garden bed is with cinder blocks or heavier concrete blocks. Your budget will vary depending on how large your garden is and the type of plants and flowers you want to grow. To make a cinder block garden bed, first prep the ground.

How do you build a raised cinder block garden?

The quick-and-dirty way of building a raised cinder block garden is to arrange the blocks, fill in the perimeter with dirt, and start planting. But there’s a little more to it if you want it to thrive and look beautiful, too. Here, we’ll walk you through how to create a four-by-eight-foot cinder block garden bed.

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