How To Build A Cinder Block Raised Garden Bed (2024)

FAQs

Are cinder blocks good for raised garden beds? ›

There are a lot of options when it comes to the material used to build a raised bed border. Wood is a common choice. Bricks and stones are good options, too. But if you want something cheap and attractive that's not going to go anywhere, you can't do better than cinder blocks.

I planted each of these cloves in its own cinder-block hole. Each one will grow into a full bulb. I also planted two bunches of basil, two bunches of cilantro and one bunch of oregano. Each of these grows in its own cinder-block hole as well.

Dampen the footing surface with water and place a one-inch bed of mortar on the footing. Furrow the mortar bed using the tip of the trowel to create a “v” to help distribute the mortar evenly. The mortar should be workable but firm enough to support the weight of the block.

Leaving a 1/4″ gap between every third cinder block, place the blocks hole side up. 20 blocks will give an interior bed area of 4′ x 8′.

Stay away from old-fashioned cinder blocks, which may contain heavy metals—not a good thing for food gardens. Second, a concrete block bed can affect your soil's pH, making it more alkaline, so it's not good for growing acid-loving plants like blueberries.

Prepare the Site and Lay the Anchor Block

Building a raised bed to last will require some hard labor but after it's done the bed will last for years to come. It will take 32 concrete blocks and 16 caps to build this raised bed. The first anchor block will take the longest to set in place.

I decided to place most of the cement blocks with the holes facing up, instead of on edge, as I had the idea to fill them with soil and plant in them. I wasn't sure how much the plants would like this arrangement, but it turns out that I picked the right type of plant and it worked out very well!

If you plan to use blocks as a raised bed material -- and many people do – and you are concerned about potential risks, you could seal the blocks with polymer paint.

They should have at least 8 inches of soil depth to accommodate the root systems of plants, because the majority of plant roots require 6 – 8 inches of soil for healthy root growth. A depth of 8 – 12 inches will suffice for most gardening situations.

Soil is the foundation of your garden, and you want it to be healthy so you can set your plants up for success! We recommend buying high-quality, nutrient-rich soil in bulk. Or, you can make a soil mix with equal parts topsoil, organic materials (leaves, composted manure, ground bark), and coarse sand.

Do cinder blocks leach chemicals? ›

There is a lot of research on this because of how often concrete is used for everything. There is some leaching but it is extremely slow and extremely low levels.

Lay out the first layer of cinder blocks.

Put ³⁄₈ inch (0.95 cm) plywood spacers in between the blocks. You will use spacers for straight walls and walls with turns.

Sleeve Anchors – sleeve anchors have excellent holding values in the block and can be used in all three sections of the cinder block with relatively high success rate. They are easy to use; come pre-assembled and come in a variety of different diameters and lengths to meet most cinder block fastening applications.

Filled Blocks Promote More Efficient Drainage

You may end up with entire sections of a retaining wall that need replacing. You can avoid a situation like that entirely by filling your hollow blocks with gravel or other stones.

We had never heard of this and after some internet research and speaking with an expert we have learned the problem is when these bricks are made with Fly Ash (which ours are - an 8% concentration) which is a by-product of coal - they can leach things such as radium and arsenic.