Building a DIY cinder block raised garden bed is cheap and easy to do. The best part is that you can put it anywhere, even over the top of the grass.
You can also customize it to make it as small or as large as you need, and to fit it perfectly into any size space that you have.
In this post, I will show you exactly how to build a raised garden bed with concrete cinder blocks, step-by-step.
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How Much Does It Cost To Build A Cinder Block 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.
Of course, that price doesn’t include the cost of the soil or plants, which will likely be the most expensive part of this project. So be sure to budget for that.
Are Cinder Blocks Safe For Raised Beds?
The short answer is “it depends”. Back in the olden days, these blocks were commonly made from ash, and that’s where the term “cinder block” comes from. But these days, they are made out of concrete and not cinder ash.
Because of the ash, old cinder blocks can leach chemicals into the soil, and you don’t want that if you’re growing vegetables. However, if you buy them brand new from the store, then they are most likely made from cement, which is safe to use for a garden.
If you want to be sure you’re building your beds out of concrete rather than true cinder blocks, then just ask the retailer before you buy them.
The two terms are used interchangeably, and “cinder block” is the more common one (heck, the sign at my local home improvement store says that on it, even though they are made with cement).
Tips For Building A Raised Garden Bed With Concrete Blocks
Building a raised bed with cinder blocks is pretty easy, but there are a few important steps you should take to ensure that they look great and fit into the space where you want to put them.
Choose The Location
First, you need to decide on a location. Be sure to choose a spot that is fairly level and gets plenty of sun (here’s how to figure out the sun exposure of your garden).
Then decide on how many cinder block garden beds you want to make. If you’re going to build more than one, you should allow plenty of space between them so that you can easily walk around and reach every corner. I recommend spacing them 2-4′ apart.
Proper spacing is even more important if you build them on top of the grass, and you need to be able to mow in between them.
Create Your Design
Since the blocks are square, and they are all the same size, designing your concrete block raised bed could not be any easier. All you need to do is measure the size of the space where you want to put it.
As you come up with your design plan, be sure to also think about how easy it will be to work in your beds. You don’t want them to be too wide, or it can be difficult to reach the middle.
How Many Cinder Blocks Do I Need?
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.
Once you determine how large your garden will be, it’s easy to figure out how many blocks you need to buy so you won’t have any left over.
The Best Soil To Use
As I mentioned above, cinder blocks are cheap – but buying the soil to fill your new garden bed will probably be your biggest expense for this project. I know it’s easy to think about pinching pennies here… but don’t.
When it comes to gardening, the quality of the soil is super important. It’s the foundation in which plants grow, and they simply cannot thrive in cheap fill dirt.
So, whatever you do, be sure to fill your beds with high quality soil. You can buy compost in bulk, or mix your own quality soil to save money.
How To Build A Cinder Block Garden Bed
Below I’ll walk you through how to make these easy concrete block raised beds in your garden, step by step. Here are the supplies you’ll need, along with the detailed instructions:
Supplies Needed:
- Concrete cinder blocks
- Good quality garden soil
- Tape measure
- Work gloves
- Wheel barrow
- Spade shovel
- Marking paintor spray paint (optional)
- Thick cardboard or newspaper (optional, use if you’re going over grass)
- Tamper tool(optional, needed for leveling the blocks)
- Level (optional, use if you want to make sure your blocks are level)
- Square garden spade (optional, use if you want to remove the sod under the blocks to level them)
Steps:
Step 1: Lay out your design – The first thing to do is to lay out the concrete blocks so that you can make sure everything fits into the space you have planned.
It’s much easier to move them around or change the design if you need to at this point than it will be later on in the project. Be sure to wearthick gloves when moving the blocks to protect your hands from the rough surface.
Step 2: Ensure the blocks are straight – Once you have the blocks laid out, use the tape measure to create a straight line.
Then mark the line using the marking paint. This line will act as a guide to ensure you’re keeping everything straight during the next steps.
Step 3: Remove the grass and level the blocks (optional) – If the area where you’re building your raised garden bed is fairly level, and the cinder blocks lay pretty flat, then you can skip this step if you want to.
But, if you’re putting it on top of your lawn, or the surface is uneven, then it’s a good idea to take the extra step to remove the grass so the blocks will sit level.
The blocks will settle over time regardless, but removing the grass will help to ensure they stay in place so your bed doesn’t become lopsided or uneven.
You don’t have to remove all of the grass, just the section that sits directly below the blocks. The grass in the center of the bed can remain in place.
To make it easy, use a square garden spade to dig out the sod. Then you can use a tamper tool to flatten the ground before laying the block, and a level to help you ensure they are straight.
Step 4: Lay cardboard under the cinder blocks(optional) – This is another optional step, and not required if you’re building your concrete beds on top of soil or rock.
But, if you want to lay them right over the grass or weeds, then I highly recommend putting down a thick layer of cardboard first. This will smother the grass and keep it from growing into the beds.
If you don’t have cardboard, you can use a thick layer of newspaper instead (at least 10 sheets thick). Learn more about smothering weeds and creating a no dig garden bed here.
Step 5: Fill the bed with soil – Once you’re done building your beds, it’s time to fill them with soil. We found it easier to temporarily remove one block so that we could push the wheelbarrow into the bed, rather than trying to dump the soil over the top.
Don’t forget to fill the holes in blocks with soil so you can use them as planters. If you don’t like that idea, then you can fill them with rocks or cheap dirt instead of garden soil, and then cover them with concrete retaining wall caps to give them a more finished look.
Just be sure to fill them with something to weigh them down and hold them in place, otherwise they can move around easier.
Step 6: Add the plants – Planting your new cinder block raised garden bed is the fun part. Just be sure to give it plenty of water after you’re done planting everything to give them a healthy start.
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.
More DIY Garden Projects
- How To Make A ConcreteCinder Block Planter
- How To Make A Zen Garden In Your Backyard
- How To Make A Cheap DIY Compost Bin
Share your tips for building a concrete block raised bed garden in the comments below.
Print Out These Instructions
How To Build A Cinder Block Raised Bed
Anyone can build these concrete cinder block raised garden beds, it doesn't require any special skills. This easy DIY project takes only a few hours, and is very inexpensive - requiring only a few basic tools.
Active Time3 hours
Total Time3 hours
Materials
- Concrete cinder blocks
- Soil for raised beds
- Thick cardboard or newspaper (optional, use if you’re going over grass)
Tools
Instructions
- Lay out your design - Lay out your design to ensure the raised bed fits into the space. It's much easier to move the blocks around or change the design at this point than it will be later on. Be sure to weargloves when moving the block.
- Ensure the blocks are straight - Once your design is laid out, use the tape measure to create a straight line, and mark it using the marking paint. This line will act as a guide to ensure everything is straight during the next steps.
- Remove the grass and level the blocks (optional) - If you're building on top of your lawn, or the area is uneven, it's a good idea to remove the grass so the blocks sit level. You don't have to remove all of the grass, just the section that sits directly underneath the blocks. To make it easier, use a square garden spade to remove the sod. Then you can use a tamper tool to even out the ground before laying the block, and a level to ensure the blocks are straight.
- Lay cardboard under the cinder blocks(optional) - This optional step is not required if you're building the raised bed on top of the soil. But if it's on top of the lawn, put down heavy cardboard to smother the grass. If you don't have cardboard, you can use a thick layer of newspaper (10 sheets thick).
- Fill the beds with soil - Once all of the blocks are in place, fill the bed with soil. If you're using a wheelbarrow, temporarily remove one block so that you can push it into the bed. Don't forget to fill the holes in the blocks with soil so you can use them as planters. If you don't want to do that, then fill them with rocks or cheap dirt instead. That will save you a few bucks, and prevent the blocks from moving.
- Plant your shiny new concrete block raised bed! This is the fun part. Once you're done planting, water your beds well. Keep in mind that the soil will settle over the first few days and weeks, so you may need to add more to fill in the spaces.
Notes
- Standard cinder blocks are 12" (1 foot) long, so you can easily do the math to figure out how many you will need to build each bed. (My beds are 4' x 7', which required 20 blocks per bed.)
- Even though they're commonly called "cinder blocks" most modern ones are made from concrete, which are non-toxic and safe to use in the garden.
- The concrete blocks are heavy, so make sure you are either strong enough to lift them on your own, or have someone who can help with the heavy lifting.
