How to Build a Raised Garden Bed

Planning, Building, and Planting a Raised Garden Bed

December 21, 2018
raised-garden-bed

Learn how to easily build your own raised garden bed!

Crestock

Raised garden beds are fairly easy to construct, even easier to maintain, and offer myriad benefits for your garden (and you)! Here’s how to build a raised garden bed in your backyard, as well as some advice on using the right wood and soil.

Raised beds are an easy way to get into gardening! Whether you purchase a kit or build your own, there are many great reasons for using raised bed gardening.

What is a Raised Garden Bed?

A raised garden bed (or simply “raised bed”) is a large planting container that sits aboveground and is filled with soil and plants. It is a box with no bottom or top—a frame, really—that is placed in a sunny spot and filled with good-quality soil—to become a source of pride and pleasure, and a centerpiece of the garden.

Why Should I Build a Raised Garden Bed?

Raised beds have many benefits. Here are a few reasons why you should consider using one:

  • Garden chores are made easier and more comfortable thanks to less bending and kneeling. Save your knees and back from the strain and pain of tending the garden!
  • Productivity of plants is improved due to better drainage and deeper rooting.
  • Raised beds are ideal for small spaces where a conventional row garden might be too wild and unwieldy. Raised beds help to keep things organized and in check.
  • Planting in a raised bed gives you full control over soil quality and content, which is especially important in areas where the existing soil is rocky, nutrient-poor, or riddled with weeds.
  • Raised beds allow for a longer growing season, since you can work the soil more quickly in the spring in frost-hardened regions, or convert the bed into a cold frame in the fall.
  • Fewer weeds are seen in raised beds thanks to the bed being elevated away from surrounding weeds and being filled with disease- and weed-free soil.
  • Raised beds allow for easier square-foot gardening and companion planting.

Learn more about the benefits of raised garden beds

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Choosing the Right Wood for Raised Beds

Many people are concerned about the safety of their wood frame. First, rest assured that CCA pressure-treated wood is banned, as it was known to leach arsenic. To ensure that the wood lasts, there are several options:

  • Regular pressure-treated lumber sold today has a mixture of chemicals applied to prevent the moist soil and weather from rotting it. Although pressure-treated wood is certified as safe for organic growing, some people have reservations about using it, and there are various eco-friendly alternatives. 
  • More expensive woods, such as cedar, contain natural oils which prevent rotting and make them much more durable. They are more expensive to buy, but they will last many more years.
  • Choosing thicker boards can make the wood last longer. For example, 2-inch-thick locally sourced larch should last 10 years, even without treatment.
  • Avoid using railroad ties, as they may be treated with creosote, which is toxic.

Alternatives to wood include concrete blocks or bricks. However, keep in mind that concrete will increase the soil pH over time, and you will have to amend the soil accordingly to grow your best garden.

How Big Should Your Raised Bed Be?

  • First, you need a location that has level ground and gets the right amount of sunlight (6 to 8 hours per day). This should narrow down your options a bit.
  • In terms of bed size, 4 feet is a common width. Lumber is often cut in 4-foot increments, and you also want to be able to access the garden without stepping into the bed. Making the bed too wide will make it difficult to reach the middle, which makes weeding and harvesting a pain.
  • Length isn’t as important. Typical plots are often 4 feet wide by 8 feet long or 4 feet wide by 12 feet long. Make your bed as long as you like or build multiple raised beds for different crops.
  • The depth of the bed can vary, but 6 inches of soil should be the minimum. Most garden plants need at least 6 to 12 inches for their roots, so 12 inches is ideal.

Preparing the Site for a Raised Bed

  • Before you establish the bed, break up and loosen the soil underneath with a garden fork so that it’s not compacted. Go about 6 to 8 inches deep. For improved rooting, some gardeners like to remove the top layer (about a spade’s depth), dig down another layer, and then return the top layer and mix the soil layers together.
  • If you’re planning to put your raised bed in a space currently occupied by a lawn, lay down a sheet of cardboard, a tarp, or a piece of landscaping fabric to kill off the grass first. After about six weeks (or less, depending on the weather), the grass should be dead and will be much easier to remove.

Building a Raised Garden Bed

  • To support timber beds, place wooden stakes at every corner (and every few feet for longer beds). Place on the inside of the bed so that the stakes are less visible.
  • Drive the stakes about 60% (2 feet) into the ground and leave the rest of the stakes exposed aboveground.
  • Ensure that the stakes are level so that they’re in the ground at the same height, or you’ll have uneven beds.
  • Set the lowest boards a couple inches below ground level. Check that they are level.
  • Use galvanized nails (or screws) to fix the boards to the stakes.
  • Add any additional rows of boards, fixing them to the stakes, too.

Check out our video on how to build raised beds for your vegetables:

Soil for Raised Garden Beds

The soil blend that you put into your raised bed is its most important ingredient. More gardens fail or falter due to poor soil than almost anything else. 

  • Fill the beds with a mix of topsoil, compost, and other organic material, such as manure, to give your plants a nutrient-rich environment (see recipes below). Learn more about soil amendments and preparing soil for planting.
  • Note that the soil in a raised bed will dry out more quickly. During the spring and fall, this is fine, but during the summer, add straw, mulch, or hay on top of the soil to help it retain moisture.
  • Frequent watering will be critical with raised beds, especially in the early stages of plant growth. Otherwise, raised beds need little maintenance.

Raised Bed Soil Recipe

For a 4x8-foot raised bed:

  • 4 bags (2 cubic feet each) topsoil (Note: Avoid using topsoil from your yard, as it may contain weeds and pests.)
  • 2 pails (3 cubic feet each) peat moss
  • 2 bags (2–3 cubic feet each) compost or composted cow manure
  • 2-inch layer of shredded leaves or grass clippings (grass clippings should be herbicide- and fertilizer-free)

Makes enough for a depth of about 9 inches.

Raised garden bed. Photo by Oregon State University/Wikimedia Commons.
Square-foot gardening in a raised bed. Photo by Oregon State University/Wikimedia Commons.

Planning a Raised Bed Garden

To plan out the perfect garden for your space, try the Almanac Garden Planner! In minutes, you can create a garden plan right on your computer.

The Garden Planner has a “Raised Garden Bed” feature. It also has a specific square-foot gardening (SFG) feature, which involves dividing the bed into squares to make the organization of your garden a lot simpler (see photo above).

Which ever garden you select, the Garden Planner will show you the number of crops that fit in each space so you don’t waste seed or overcrowd. There’s even a companion planting tool so you plant crops that thrive together and avoid plants that inhibit each other.

Test out our Garden Planner with a free 7-day trial—plenty of time to plan your first garden! If you enjoy the Garden Planner, we hope you’ll subscribe. Otherwise, this is ample time to play around and give it a go!

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Learn More

Have you ever thought about building your own raised garden bed? Or do you have one already? Tell us about it below!

Reader Comments

Leave a Comment

Hi I have a LOT of old wood

Hi I have a LOT of old wood from the prebious owners of my house that I would like to turn into raised beds. I'm worried about cca in the wood that could leech into the soil. Is there a way to test for or prevent this?

This link gives information

The Editors's picture

This link gives information on how to identify if your wood has been treated with CCA, including where to purchase arsenic testing kits: http://www.beyondpesticides.or...
If in doubt, do not use anywhere near your edible plants.
 

I am building my first raised

I am building my first raised beds this year and would like to use rail road ties as my borders...is this safe or should I go with untreated material

We'd avoid railroad ties,

The Editors's picture

We'd avoid railroad ties, even old ones. They leach toxic chemicals for decades. Concrete blocks are an inexpensive substitute.

I didnt find any guidelines

I didnt find any guidelines to build a garden bed in this article. Is it been removed ?

Also I have found some websites from where we can purchase the garden beds online like raisedgardenbed.net.au and birdiesgardenproducts.com.au
Is it fine if I purchase garden beds from there and start my home garden ?

Thanks for writing! We are

The Editors's picture

Thanks for writing! We are not sure why the content has disappeared and will look into it! Very odd!

Hi, check out you tube for

Hi, check out you tube for building your own from old pallets. Lots of firms will give the away for free and the timber is perfect for this job. Good luck Steve.

I have noticed different

I have noticed different heights of raised garden beds. Other than building high for the convenience of not having to bend over, are there recommended heights/depths of beds for different types of vegetables?
Very informative site. Thank you.

The most common height for

The Editors's picture

The most common height for raised beds is probably 12 inches. This allows for sufficient drainage for most crops. It assumes you have 12 inches or so of good soil beneath the beds. You can go higher (up to 24 inches) if you have a bad back but then you may need to build cross-supports because the sides of the bed could bow from the weight.

Is it recommended to install

Is it recommended to install a drainage system in a concrete block raised bed to prevent the creation of a mud pit?

Raised beds tend to dry out

Raised beds tend to dry out relatively quickly, and are often used to make it possible to grow a garden where soil drainage is poor, so you should not normally experience problems with drainage in a raised bed. Make sure to mix the soil below with the bed with the soil you’re adding to the bed to prevent the water sitting on top of the garden soil, especially if you have very heavy clay soil. If you're worried that the water will pool on top of it you could leave a few small gaps between the blocks, or drill some holes in them, to let the water escape.

We want to put raised beds in

We want to put raised beds in the backyard and have septic tanks back there somewhere. The grass grows very well over the tanks - would a raised bed be a mistake over the tanks?
Thanks for your advice.

This is a bit of a grey area

The Editors's picture

This is a bit of a grey area so we'll advise you best we can: There is a risk of contamination from growing near septic tank leach fields as it’s not always easy to know if the system is working perfectly. As long as the system is working perfectly then you should be able to grow a some edible crops above it, however it’s generally thought that raised beds can reduce the evaporation of moisture from the soil, which isn’t good for the system.
Definitely avoid growing root crops and perhaps leafy greens near a septic tank. Fruiting vegetables such as tomatoes whose fruit is held high above the soil surface should be fine. Personally, I’d consider planting shallow-rooted, pollinator-attracting flowers in the septic tank area instead.
 

I am building a raised garden

I am building a raised garden and wondering if i should put some sort of material under the soil? I am afraid the grass will shoot up through the soil if I dont? What do you recommend?

If placed directly onto

If placed directly onto grass, it’s possible that grass and weeds will grow up through the bed. A good option is lining the base of the bed with a porous material such as overlapping sheets of cardboard, several layers of newspaper, or landscape fabric to stop unwanted plants growing up into the bed while still allowing water to soak away.

I would like to build a

I would like to build a raised bed garden on top of an old basketball pad which gets total sun all day long. Would this cause too much heat from the sun heating up the concrete? Thank you, Ron

I wouldn’t be too concerned

I wouldn’t be too concerned about the heat as the raised bed will shade the surface beneath, but I would be worried that the solid surface beneath the beds would cause problems with drainage. You would need to either break up or remove the concrete below the bed, or else make gaps in the sides of the bed for water to escape.

I have been preparing a

I have been preparing a portion of our yard this week to start a raised bed vegetable garden. I am using organic soil and seeds, so the safety of my vegetables is important to me. I have the garden next to the house, but have read that this may be a bad thing to do because of possible contaminants. Our house is lead-free of paint, but are there other contaminants to worry about? I guess I should have our soil tested. If I want the organic soil in the beds to be as pristine as possible, should I place a barrier between the organic soil and our current soil? Landscape fabric? Rocks? I'm not sure. Thanks so much for any advice.

Many people do grow close to

Many people do grow close to their house without problems, and it's not something I would personally worry about too much, but if you're very concerned at all I would recommend having your soil tested and seek expert advice on the findings.

Thank you. I did have it

Thank you. I did have it tested for arsenic and lead and the levels came back within normal limits.

Also, for the love of Pete,

Also, for the love of Pete, calling the hard rock-like stuff in your driveway cement is the same as calling a cake by the name flour. It's concrete, of which cement is a component.

Hey, really there's no need

Hey, really there's no need for unnecessary ruddiness. But, to be that completely technical guy....

Cement was actually patented in the mid 1800's in Europe and anything from there after of similar mixture in the United States become known as concrete.
Essentially the same thing but known as a different name.
Now It is also true that what we call in the US cement doesn't always have to be of the substance in which was patented in Europe. Similar to the all cactus plants are under the classification of succulents but not all succulents are cactus. We have advanced the word into many other meanings. Such as "rubber cement" or "cement adhesive."

Hence to say, it's a common and reasonable mistake to Americans depending on your generation line I would guess. But to say calling cake by the name of flour is super extreme and can only have the intent to be hurtful and obnoxious. It's a common reality even in the days of 1800's we can say, that flour, and cake, are two separate things. And seeing how you have to mix flour to create a cake makes this example just plan nonsense. You don't need cement to create concrete. Cement and concrete are the same ingredients just mixed to different recipes.

Thank you...
Now please don't purposefully make a comment intending to be hurtful again.

CCA has never been banned, it

CCA has never been banned, it was a voluntary effort by manufacturers to stop using it in response to public outcry regarding its use in boardwalks and children's play equipment.

http://www.epa.gov/oppad001/re...

An easy way to ensure that your lumber wasn't treated with CCA is that most companies now use copper azole, which turns the lumber green (copper). If your lumber is green, it was not treated with CCA.

I have 20 "storage

I have 20 "storage containers" I got to use as raised bed gardens. They are 32"x 48" and 16" high with 5" gap between ground and bottom of box. They are made with a pressed/composite type wood. They were used to ship auto parts. My ? Is what can I use to paint/protect the outside if them to prevent weathering. The inside I was recommended to line with plastic.

There are many eco-paints on

There are many eco-paints on the market these days for wood; your local hardware shop may stock them, or look online. Raw linseed oil (as opposed to boiled linseed oil, which is mixed with solvents) can be used too. Lining the inside with plastic is a great idea, but if you're extending this across the base remember to make plenty of drainage holes.

Can you use old tires for

Can you use old tires for raised garden beds?

Sure, old tires stacked on

Sure, old tires stacked on top of each other work especially well for potatoes.

I am considering purchasing a

I am considering purchasing a 1 inch thick cedar for my garden bed, because I cannot find a 2 inch thick cut. Is 1 inch thick enough?

Consider connecting 1-inch

Consider connecting 1-inch thick cedar boards with 2-inch-long brown screws (sold in most home improvement stores) or 3-inch deck screws. Drive screws through the side boards of the beds into four-by-four vertical posts in each corner.

My lawn is Bermuda grass. A

My lawn is Bermuda grass. A first try at a raised bed (after digging out a place in the back lawn) resulted in Bermuda eventually taking over the bed. It loves water! An old blacktop pad seems a good spot for the bed if the soil is deep enough. There's enough sun. But, will that work?

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