These are actually concrete block garden beds covered in surface bonding cement, but that was too much of a mouthful for a title. Ha!
I wanted to plant some berry plants along our fence line, parallel to our septic lines, but I didn’t want well….poop berries or a ruined septic system, so I needed to come up with a way to contain the berries and keep them the requisite 10 feet away.
Concrete block beds seemed like a good choice, but I didn’t want them to look like concrete blocks. I found this QuikWall product from Quikrete that not only pretties up the blocks a bit but also literally cements them together into a sturdy, permanent structure. It was all a bit of an experiment because the only tutorials I could find when I started this project last year, were for small walls. It made sense though that if this stuff can make walls sturdy then it could handle a foot tall garden bed…And it did!
*I used 19 concrete blocks, 19 caps, and about 1.5 bags of surface bonding cement per bed. I found my concrete blocks from Home Depot for $1.45 a piece.
*I wasn’t able to find QuikWall at my local big box store, although I think some locations carry it, so I ordered it through my local tile shop.
**You want to use a gravel that can be compacted like what is used in driveways. I used granite gravel with “minus” or gravel dust that gets in between the rocks and helps it compact so that when you walk on it, you don’t sink. Do not use pebble gravel or any gravel that has smooth rocks. This will not compact and will create an unsteady base for your blocks.
I put together a video tutorial below that documents what I did. It shows you how the mixture looks being spread on, which is probably the most helpful part. I still recommend reading the written tutorial because there are lot of details that I didn’t include because it would have made the video too long.
I sometimes use the word “cinder” in place of “concrete” when describing these concrete blocks. To a lay person, these terms are often used interchangeably and I wanted to use terms that would be easily recognized. I also used them interchangeably, not knowing there was an important difference, until I shared this post.
Older cinder blocks are made with fly ash and contain chemicals that can be harmful to your health. Newer concrete blocks that you can get at the hardware store do not contain fly ash. They are made of water, stone, and concrete and they are safe for food. If you are using these beds to grow food, please use new concrete blocks.
Gardening is a rewarding and relaxing hobby that allows you to grow your own fresh fruits, vegetables, and flowers right in your backyard. And using raised garden beds can make gardening even easier and more accessible. Poured concrete is one of the best materials for constructing durable, long-lasting raised beds. In this comprehensive guide, we’ll walk through everything you need to know to build your own poured concrete raised garden beds from start to finish.
What are Poured Concrete Raised Beds?
Poured concrete raised beds are a type of gardening bed that sits above ground level They are constructed by building a wooden form, then filling it with wet concrete that hardens into a solid, sturdy bed.
The main benefits of poured concrete raised beds include
-
Durability – Concrete is extremely tough and can last for decades without rotting or deteriorating. This makes poured concrete a great long-term investment.
-
Weed Prevention – Concrete forms an impenetrable surface that prevents weed growth up from the ground. This reduces maintenance.
-
Customization – Concrete can be poured into any shape or size bed you desire. You can make square, rectangular, circular, or curved beds.
-
Height – Concrete beds can be made taller more easily than other materials, allowing for improved ergonomics.
-
Low Maintenance – Other than occasional cleaning, concrete raised beds require very little ongoing care and maintenance.
Design and Material Considerations
When planning your poured concrete raised beds, there are a few key factors to consider:
-
Size – Typical raised beds range from 2-4 feet wide and 8-12 feet long. Make sure to leave at least 2 feet of space between beds for walking.
-
Height – Most raised beds are between 6-18 inches tall. Shorter beds (6-8 inches) are good for access, while taller beds (12-18 inches) raise plants to a more comfortable working height.
-
Shape – Square and rectangular beds are the most common, but you can make any shape that fits your space.
-
Location – Pick a sunny, flat spot in your yard with good drainage. Avoid low areas that collect water.
-
Soil – Pouring concrete forms the structure only – you’ll still need to fill the bed with good quality gardening soil and compost.
-
Concrete Mix – Use a high strength 4000+ PSI concrete mix without large aggregates. Fiber reinforcing is also recommended.
-
Wood for Forms – Use good quality plywood or dimensional lumber to build sturdy forms. Waterproofing the wood helps achieve clean concrete edges after removal.
Building the Wooden Forms
The first step in creating poured concrete raised beds is constructing a wooden form to hold the wet concrete as it hardens. Here’s an overview of how to build raised bed forms:
Materials Needed
- 3/4″ plywood or 2x lumber for sides
- 2x lumber for base
- Screws and/or nails
- Wood glue (optional)
- PVC pipes – Used to create drainage/planting holes
- Form release agent
- Mineral oil to treat wood
Cutting the Pieces
Use a circular saw to cut the following form pieces out of plywood or dimensional lumber:
- Sides – Cut 4 pieces the length you want your bed, typically 8-12 feet. Rip to desired height, usually 6-18 inches.
- Ends – Cut 2 pieces the width you want your bed, typically 2-4 feet wide.
- Base – Cut 1 piece the exact interior dimensions of the form.
Assembling the Form
Screw or nail the sides to the base, making sure corners are square. Then attach the end pieces between the sides. Use wood glue for extra strength if desired.
Insert PVC pipes in the bottom at intervals to create drainage and planting holes in your finished bed.
Finally, coat the inside of the form with a release agent so concrete won’t stick to the wood.
Mixing and Pouring the Concrete
Once your form is built, it’s time to mix and pour the concrete:
-
Concrete Mix – Use a high strength 4000+ PSI mix without large aggregate. Add fiber reinforcement.
-
Water – Only use as much water as necessary for proper concrete consistency to avoid weakening the concrete.
-
Mixing – Mix concrete in a wheelbarrow or with a power mixer. Hand mixing in small batches also works. Thoroughly blend concrete and water.
-
Pouring – Pour concrete into the form in layers, tamping frequently with a board to compact it and minimize air pockets.
-
Finishing – Screed off excess concrete flush with the top of the form using a straight 2×4. Then float or trowel the surface smooth.
-
Curing – Cover the poured concrete with plastic sheeting and mist with water for 1-2 weeks to cure properly. Do not remove forms or handle concrete during this time.
Removing Forms and Using Your Concrete Beds
After allowing the poured concrete to fully cure:
-
Form Removal – Remove screws/nails and carefully separate the form boards from the hardened concrete.
-
Filling – Add good quality garden soil mixed with compost up to 1-2 inches from the bed’s top.
-
Planting – Your concrete raised bed is now ready for planting seeds and transplants! Add mulch on top of the soil to help retain moisture.
-
Drainage – Make sure beds have drainage holes/gaps to prevent excess water buildup. Add gravel, sand or decomposed granite in the bottom below the soil to improve drainage.
-
Maintenance – Occasionally hose down the concrete to clean. Replenish soil nutrients each season by top dressing with compost.
Building your own poured concrete raised garden beds is a satisfying DIY project that results in beautiful, functional beds that will enhance your garden for years to come. With some basic construction skills and materials, you can create custom raised beds tailored exactly to your space and gardening needs.
Step Two: Prep the area and remove the grass.
Remove any grass or weeds from the area and start leveling out the ground if you’re on an incline. The gravel that will be added in the next step will help with the leveling a little bit too, so don’t worry if it’s not perfectly level at this point.
If you have rocky soil like I do, then I highly recommend using a pick axe rather than a shovel. It will save you so much time and frustration.
Step Four: Add concrete blocks.
Now is the time to get picky about leveling. As you add your concrete blocks, ensure that they are perfectly level. You may have to add or subtract gravel to get this just right. I also recommend re-compacting any disturbed gravel, which I didn’t always do and ended up regretting later (I’ll explain at the end).
This step takes the longest, but it’s very important to get right as it determines the stability of the beds and makes the next steps much easier.
Concrete Raised Planter
FAQ
Is concrete good for raised garden beds?
Raised beds can be placed on paved surfaces, including concrete and asphalt, with some modifications to support drainage and healthy plant roots.
How to maintain a concrete raised garden bed?
Due to quick drying, ensure deep, regular watering to maintain soil moisture. Lateral watering throughout the bed is very important, ensuring water reaches deep down below rather than just a few inches on the top. Ensure the whole bed is getting water, not just isolated areas.
Are concrete sleepers safe for vegetable gardens?
Concrete sleepers a durable, low-maintenance, chemical-free solution for raised garden beds. They are resistant to rot, insects and unaffected by moisture. They are also free from chemicals, which makes them safe for growing food.
What to put under raised garden beds on concrete?
You Can Use a Layer of Cardboard at the Bottom of Raised Beds to Prevent Weeds If your budget doesn’t allow for weed barrier cloth, you can add several layers of cardboard to the bottom of your raised bed before filling it with soil. The cardboard will decompose in about 4 to 6 months.