How to Build a Raised Garden Bed That Will Last

I’ve built raised garden beds out of railroad ties or cedar fencing, 2x4s, bricks and even a beautiful woven lattice. But when I got serious about not having to build new raised beds every few years, I developed a simple, sturdy design that anyone can follow.

It is the only way I’ve bothered making raised beds for the last 10 years, regardless of where I was building them—the Arizona desert, rainy Pacific Northwest or suburban Georgia. This design will provide you with a financially reasonable and technically easy way to get beds together quickly for any sized space. It offers a better amount of bed depth than most plans I see, and requires very few tools. The sturdiness of the beds mean they won’t move over time, lean over, and are impervious to getting dinged up by your wheelbarrow.

Use the right wood

The most common mistake I see for raised bed building is not choosing the right wood. A lot of time is often spent on considering pressure treated (PT) wood versus untreated, or what variety of wood—cedar versus redwood. But the biggest problem is that people generally get lumber that’s too thin and/or small. Messing around with cedar pickets, which are thin and flimsy, or 2x4s, which don’t give you any vertical height, doesn’t serve you long-term. The answer is to go large: I use 2x12s or 2x10s. This means that you need fewer planks of wood stacked vertically. I don’t use pressure-treated wood, because even though the methods they use currently to treat the wood aren’t considered toxic, I go out of my way to not introduce unneeded chemicals into my edible garden.

While you can use variety you want, and hardwoods or cedar will certainly last longer, it’s not essential. Using pine or redwood, in planks of wood this beefy, will still last eight years or longer. When the wood breaks down, it benefits your garden because it’s essentially compost, and by keeping the beds inexpensive and easy to make, creating new ones in eight to 10 years won’t seem cumbersome. 

Check out suppliers other than big box stores

Big box stores aren’t the only game in town for getting wood. Look specifically for lumber stores and get some prices, or—my favorite hack—hit up Craigslist for independent millers selling “rough cut” wood.

The benefit of independent millers (people with their own saw mill or setup) is that the wood is likely to be cheaper, and you might get a deal for all the cuts you need. Also, independent millers don’t cut everything down to the same length just for uniformity, like you get at Home Depot. As they’re slicing a tree into 2x12s, if the plank ends up being 15 feet long, and you only need 12, they don’t chop the last three feet off, because it’s just more work, and there’s no benefit to doing it. As a result, you get longer cuts for the same price, while supporting someone local. While I don’t see it as a downside, this wood is usually “rough cut”—it hasn’t gone through a sanding process to make the sides smooth. They also have not been kiln dried as they would be for a big box store, meaning they still hold a lot of moisture. For the purpose of building raised beds, neither of these issues is a problem. The raised beds will live outside under constant watering, and really doesn’t require the smooth sides. I actually prefer the rough cuts; I think it makes the beds less inviting to pests. 

Determining the size of your beds

A raised bed is a rectangle. That rectangle can be any length you want; you are limited only by the length of wood planks you can obtain (12 or 16 feet is common). However, in terms of the width of the bed, you want to think really hard about making it any wider than four feet (but anything in the two to four foot range is fine). There’s a simple reason: You have to be able to reach everything in the middle of the bed, and anything wider than four feet makes that quite difficult. The height of the bed will always be 22 1/2” tall, because we’ll use two 2x12s stacked vertically (and 2x12s are actually only 11 ½” once dried). Consider, as you are designing the beds, if the space you are putting them in slopes dramatically, as this might mean breaking a long bed into two, so you can terrace the ground for each bed. Make sure you allow at least three feet between beds, but four feet is better. This will allow you to maneuver a wheelbarrow through the aisles, which you’ll find really helpful. Don’t be afraid to grab some landscaping flags to lay out where the beds will go and just walk around, making sure you can reach everything and it’s comfortable to walk around. 

Sketch out the entire space, laying out the final dimensions of the beds. This is going to help you visualize the wood you need. For each bed, you’ll need one 2x12x16 for the shorter sides, and then two 2x12s for each of the longer sides, at whatever length you design the beds to be. Ideally, you get planks a little longer than the beds, so you can square off the ends of the planks. 

Determine how much wood you’ll need

The planks you lay horizontally will need vertical supports to keep the bed together. You’ll place these in every corner, and then every four feet of length along the long side. For an eight-foot-long bed, you need one additional vertical support in the middle. For a twelve-foot bed, you need two additional supports. This support is just a 2×4 that is 20” tall (roughly the same height as the beds). Add up the lengths to determine how much vertical plank you need. For instance, on an eight-foot bed, you need six vertical supports, which is 144” or a 2x4x12’ plank. For beds that are longer than 12 feet, I like to put in some additional bracing in the middle of the bed, all the way across the width. This helps stop the bed from bowing in the middle over time. The brace is just additional 2x12s, stacked vertically, the entire width of the bed. 

Credit: Amanda Blum

The tools you’ll need

The beauty of this design is that you need very few tools. You’ll benefit from a chop saw, but a circular saw will do in a pinch. Also: a power drill, wood glue, 2 ½” construction screws and a power sander, and the sander is optional.  While you can get your cuts done at a big box store, you’ll save a lot of money doing it yourself, and it’s very likely you’ll make at least one mistake on the cuts you need, so having the ability to make cuts where you’re building is very helpful. The sander is used on corners to round sharp edges. This helps reduce clothing getting caught or getting scratches as you walk around the corners of the beds, but isn’t essential. Since you’ll be using construction screws, you won’t be pre-drilling anything (and construction screws come with the right drill bit in the package), but a decent power drill, even a hammer drill, is absolutely essential.  While not essential, I benefited a lot from buying corner clamps so that I could get a real 90-degree corner on my beds. 

The build

This is obvious, but lumber is dimensional: You’re not joining up two sheets of paper. Where two pieces of wood meet in a corner (where they join), you have to be deliberate about which piece of wood is on the “outside,” through which you’ll screw into the other piece of wood. The shorter pieces should always live on the outside, and you screw through the short side, into the longer piece of wood. Because of this, when accounting for the real length of the wood you need for those long sides, you deduct the three inches (1 ½ inches from either end) because the width of the short end of the wood makes up the difference. In an eight-foot bed, rather than the long pieces of wood being 96”, you’d make them 93”. When they butt up against the short sides of the bed, they end up being 96” total length. 

Start on a flat surface, and build the first level of the bed. Join one corner, using the clamps if you have them, making sure the short length of wood is on the outside. Take the time and care to make sure the cuts are all 90 degrees, and the wood is lined up precisely. Use wood glue between the two pieces of wood. Using your drill, screw through the shorter piece of wood into the longer piece of wood. Use two screws for this, one four inches off the ground and a second about eight inches off the ground. Be sure to place the screws an inch away from the edge of the wood, and ensure you are screwing perpendicular to the wood, so it goes in straight. Continue going around the bed screwing the corners together until you have a complete rectangle. Do this a second time, so now you have two rectangles. You can usually just put the second one together on top of the first, as they should be replicas of each other. 

Next, put in your vertical supports. Place a 2×4 cut to 20” in each corner vertically. Put the longer side of the 2×4 along the longer side of the bed. Now, screw through the bed from the outside, into the vertical support, placing four screws on each side of the corner. Go around and do this in all four corners, and then every four feet along the length. The vertical support won’t be as tall as the bed—it should be a little bit shorter. This will hide the supports once you have soil in the bed, for a cleaner look. 

If the bed requires bracing in the middle, take another measurement of the distance between the width of the bed, and then cut two 2×12” inch pieces to that length. Put them in place with wood glue, and then screw from the outside of the bed into the ends of the 2x12s.

Now, move the bed into place. What I like about this process is that once you put the bed down, you’ll see precisely where you might need to level the ground a bit and can just do so with a shovel, with the bed in place. Lift the bed, dig it out a bit, and put it back down. You don’t need to be precise about pre-leveling the space. Fill the beds with good soil, and you’re ready to go. These beds are sturdy enough that you can tip a wheelbarrow into them and not damage the bed. 

You can take a sander to the corners to smooth them out a little—a power sander makes very quick work of this. I don’t stain or seal my raised beds, because I don’t want to introduce anything that can leach into the soil. However, there are whey-based stains that are okay to use in this instance. 

Image Credit: Amanda Blum