Building basic raised beds is about as easy as a project gets. All you need is your measurements, a few tools, screws and lumber.
Choosing your lumber is a personal preference. Most people recommend wood that is naturally rot resistant such as cedar, juniper or redwood. In my opinion you will want your wood to be untreated so not to contaminate your food.
The lumber we used to build the beds above was a mix of reclaimed wood from our cabin renovation a few years ago and untreated pine. The wood we are using today is untreated construction lumber. It was the only untreated wood available in the size we need. If you end up with construction lumber or a softer wood like pine that's fine too. The longevity is the only concern when using a softer untreated wood. We built our first 7 raised beds in 2016 and they look like they have plenty of years left in them. Your weather conditions and the type of wood you choose will play in to the length of your garden beds life.
As far as measurements go that is also up to you and the amount of space you have for a bed. Our garden is very large so the best measurements for us were 3 1/2ft wide by 10ft long. Ideally you should be able to reach the back of your bed if it can only be managed from one side, or you should be able to comfortably reach the middle of the bed if it is accessible from both sides. The height of our beds is about 12". This is a comfortable height for me and deep enough for my deepest rooted plants to have decent soil.
We are building a 3 1/2' x 10' bed so our measurements for this tutorial will be based on that. Our garden beds are built with 4 x 4 legs. We use a post hole digger when we place them in the ground. We dig 6 holes approximately 4" deep. The legs ensure that your garden bed will stay in place and provide overall stability to the box.
Building Materials and Tools
Two 10ft 2 x 12
One 8ft 2 x 12
One 8ft 4 x 4
3" Construction Screws
Step 1. Cut your 4 x 4 into 16" sections which will give you 6 legs
Step 2. Cut your 8ft board into two 42" (3 1/2') sections.
Now your lumber should look like this...
*Tip- From now on keep an eye on the good sides of your boards facing any knots or damage to the inside of the box.
Step 3. Attach 4 x 4 legs to the 10 ft boards. Do this by laying out your 10ft board and placing one "leg" under each end and one in the middle at the 5ft mark. Line them up flush with the top of the board. Fasten with 3" screws. We used 3 per leg. Repeat this step for both 10ft boards
Step 4. This step is easier with two people. Attach your short sides. Do this by postioning one of your 10ft boards with the legs facing up into the air. Bring one of the short ends flush with the end like this...
...when all of your sides are flush use two screws to fasten your short side to the end of your 10 ft board and one screw directly into the 4 x 4 leg like below.
Now we should be looking like this...
Step 6. Same as step 5. Attach your last side by pulling it into the box and making your corners flush like below. Fasten the last board as you have done in the last step.
Flip that puppy over and you've got yourself a garden bed!
The benefits of raised beds are plentiful. We are in Wisconsin- Zone 4, our growing period is pretty short. Our last frost day usually falls in early May. We benefit from our black raised beds doubly because the soil in them warms up much faster than the ground soil. Raised beds keep pathway weeds from your garden soil, prevent soil compaction, provide good drainage, prevent soil erosion and its the best way to control the health of your soil.
Painting the beds is controversial but of course completely up to you. I painted ours because our wood was so mismatched and some of it was really beaten up. I painted just the outside of the boxes to prevent as much leaching as possible. I used an exterior paint that was leftover from our shed. If you are worried about contamination a quick google search for "food safe exterior stain" will bring up a bunch of options.
Ideally you'll want to place your raised bed in a level location that gets full sun. Situate your beds so the long side faces south to ensure equal light reaching all of your plants.
Soil requirements for raised beds are a little different than other gardening methods. An ideal mix would be 1/3 peat moss + 1/3 vermiculite + 1/3 compost. Peat moss is another controversial garden subject that I have personally skipped using in my own garden. I use the second best option which is 1/2 topsoil and 1/2 compost. We purchased both by the truckload from our local plant nursery but you can easily find both in smaller amounts at your local home improvement store. Another great method for building up soil in your raised beds is the Lasagna Method.
Watering methods are your own preference. I prefer to water by hand to keep finicky plants leaves dry and to make sure each plant is getting their required amount of water. I find drip and soaker hoses to be a pain with multiple beds. Sprinklers tend to cover too large of an area and end up watering your paths resulting in more weeds.