While wood does make for a nice aesthetic for your raised garden bed, it will rot over time. Cinder blocks, on the other hand, make a much stronger edge that can stand up to the weather and give plants great drainage.
Cinder blocks are often confused for concrete blocks, but there is a difference despite their similar appearances. Cinder blocks are made from concrete and a cinder aggregate that makes them lighter. Concrete blocks are made from pure concrete. This feature makes it much easier for you to build a raised garden with them.
A quick and dirty way to make a raised cinder block garden is to put the blocks in place, add dirt around the edges, and then plant. 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.
Raised garden beds made from concrete blocks are an increasingly popular option for home gardeners. Concrete block raised beds offer numerous advantages over traditional in-ground gardening and other types of raised beds. In this comprehensive guide, we’ll explore the benefits of using concrete blocks to build raised garden beds and provide step-by-step instructions to create your own.
Why Choose Concrete Blocks for Raised Beds?
There are several excellent reasons to select concrete blocks when building a raised bed garden
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Durability – Concrete blocks are extremely sturdy and durable. Unlike wood or other materials, concrete block raised beds will last for many years without rotting or deteriorating.
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Affordability – Concrete blocks are an affordable option compared to things like brick, stone, or decorative wood. They can often be found cheaply or even free on sites like Craigslist and Freecycle.
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Design flexibility – Concrete blocks allow for countless design possibilities. Beds can be any length, shape or height. Blocks stack and arrange easily to create custom beds.
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Pest deterrent – The solid concrete walls act as a barrier to burrowing pests like gophers and moles. Rabbits also have a harder time accessing plants.
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Weed prevention – Concrete blocks prevent weeds from surrounding areas encroaching into the garden bed.
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Convenience – Built-in “pockets” in many concrete blocks are perfect for additional planting, trellising or adding hoop structures.
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No chemicals – Unlike railroad ties or treated lumber, plain concrete blocks don’t leach chemicals into the soil. They are safe for edible gardens.
Concrete Block Raised Bed Designs
A major benefit of building with concrete blocks is the creative freedom. Beds can be designed in straight rows, squares, L-shapes or any geometric pattern. The blocks make it easy to create unique multi-level beds, too.
Some popular design ideas include:
- Single layer blocks for shorter beds
- Double or triple stacked blocks for deep beds
- Mix of full blocks with half blocks for a staggered, interlocking design
- Incorporating decorative concrete caps or corner blocks
- Contrasting block types and colors for visual interest
Square foot gardening is an excellent approach for concrete block raised beds. The modular block layout lends itself well to organizing crops into organized square foot sections.
Step-by-Step Instructions
Building your own concrete block raised bed is straightforward. With a few simple tools and materials, you can construct a bed in a weekend:
Supplies Needed
- Concrete blocks – Standard 8″ x 8″ x 16″ blocks are typical. Calculate how many blocks are needed based on bed dimensions.
- Gravel or crushed rock – For leveling and stabilizing the base
- Sand – Helps fill in gravel gaps
- Landscaping adhesive – Use construction adhesive to secure stacked rows of blocks
- Topsoil – High-quality gardening soil for filling the bed
- (Optional) Concrete surfacing product – For capping blocks to give a smoother finish
Tools
- Tape measure
- Shovel
- Level
- Wheelbarrow
- Mason’s trowel
- Masonry hammer
- Masonry chisel
- Safety gear – Gloves, goggles, mask
Instructions
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Plan layout – Measure area and diagram shape and size of bed(s). Calculate number of blocks needed.
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Prepare site – Remove any existing grass, plants or debris. Level ground surface.
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Add gravel base – Spread 2-4″ thick layer of gravel as a foundation. Shovel on thin layer of sand.
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Arrange blocks – Place first row of blocks end-to-end onto gravel base. Check level frequently.
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Stagger blocks – Second row should have blocks offset from seams below. Use landscape adhesive between layers.
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Check level – Use level tool often to ensure blocks remain even as stacked. Adjust as needed.
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Repeat stacking – Continue adding rows to desired height, alternating direction and using adhesive.
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(Optional) Finish surface – Use concrete resurfacer to coat blocks for a smoother finish if desired.
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Add soil – Shovel high-quality topsoil into beds. Mound soil 2-3″ below top edge.
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Plant! Enjoy your new raised bed gardening space! Amend soil as needed.
With the right materials and tools, building a raised bed from concrete blocks is very achievable. The modular nature of concrete blocks makes construction simple. Maintain focus on keeping the structure level, and enjoy the flexibility to create custom beds to suit your space and style. With proper care, a DIY concrete block raised bed will provide many years of productive gardening!
How to Build a DIY Cinder Block Garden Bed
First, pick a spot for your garden bed that gets enough daytime sunlight for the plants you want to grow. To keep your new garden moist, you should also be close to a water source, or at least close enough for your garden hose to reach.
- Figure out the Size: A normal cinder block is 8 inches by 8 inches by 16 inches. Let’s find out how much a 4×8 garden needs. Long: 8 feet 12 inches, which is 96 inches, divided by 16 = 6 cinder blocks for one side of the bed, divided by 2 = 12 cinder blocks for the long edges of the garden. Width: 4 feet, which is 48 inches, divided by 16 = 3 cinder blocks, divided by 2 = 6 cinder blocks for the short edges of the garden. Garden Bed Perimeter: 12 x 6 = 18 cinder blocks. Change the math to get the cinder block garden bed size you want.
- Mark Off the Area: To mark off the edges of your bed, use wooden stakes. Then, tie a piece of string or thin rope to the stakes to make a fence around the bed.
- Prepare the Ground: Look at the ground where you are and decide how to get it ready for the bed. If you need to, cut down the grass or dig some holes to make the soil flat for planting. For better weed control, put down a layer of landscaping fabric before putting down your cinder blocks and then filling in the gaps with soil.
- Set up the cinder blocks: Place the blocks around the outside with the holes facing up. The edge of the soil and mulch you’ll be adding will be this, so make sure the cinder blocks are level and not tilted or with gaps between them.
- Adding Another Layer of Blocks (Optional): If you want a bed with higher edges, you can stack your cinder blocks, but you’ll need to double the number you calculated. Even though the cinder blocks are big, you’ll need to make sure they stay in place. Put a wooden stake or a piece of rebar through the first layer of cinder blocks’ holes. Then, put the second layer on top of the first, making sure the stake is still going through the blocks’ holes. Filling them in with dirt secures them further. When you choose the height of your bed, think about what kinds of flowers and plants you want to grow. A shorter border will make small plants stand out more, while taller plants will be able to easily grow up and over the border. For some plants, roots may need more space to grow.
- Fill Around With Dirt: Put dirt around the edges of the cinder blocks (i.e. e. , the openings in the blocks) with dirt and/or mulch. You can also fill the holes in the cinder blocks with soil to keep them in place. This also makes room for more plants if you want to garden in them.
- Fill with topsoil and plant. Put topsoil in the middle of the bed. There you have it! You can now plant any flowers, plants, herbs, or vegetables you want and enjoy your new garden.
Make a Cinder Block Raised Bed
FAQ
Are concrete blocks safe for raised garden beds?
How many cinder blocks do I need for a 4×8 raised bed?
What is the best block for a raised bed?
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.
What is a cinder block raised bed?
Cinder block raised beds are easy to make with a little hard labor and simple planning. A garden bed with cinder blocks will never rot and can last many years with little to no maintenance. The concrete blocks form a sturdy growing bed and also allow for planting in their center holes.
How thick should a raised concrete bed be?
If you build any higher than 500mm the mass of soil could overwhelm the structure. Therefore it is also important to consider the width of the bed as well as just the height. If you are building concrete raised beds higher than 500mm (two blocks) go for double thickness or 200mm thick. Do you need to line a raised concrete bed?
How many cinder blocks do you need for a raised bed?
It’s super easy to figure out how many concrete blocks you’ll need for building a raised bed, because they are all the same size. The blocks are 12″ (1 foot) long, which makes for really easy math. The beds we built (the ones in the photos) are 4′ x 7′, so we needed 20 cinder blocks to construct each one.
How much does it cost to build a raised bed?
Using concrete cinder blocks to build raised beds is very inexpensive. At my local home improvement store, the blocks are only about $1 each. So you could make a nice sized bed for about $20. But the price of the blocks will likely vary based on where you live, and the exact cost of your project depends on how large you decide to make it.
Should you build a cinder block garden?
Also, keep in mind that the soil in your raised bed will settle over the first few days and weeks, so you may need to add more to fill in the holes and spaces. If you’re looking for a cheap and easy raised bed project, then building a cinder block garden is the perfect project for you.