There are several reasons why one might venture into building a raised bed and for urban gardeners, its likely due to limited space. Raised beds are also a great way to manage weeds, and it provides access to individuals with disabilities (a bad back or knee). In any case, it is also a good idea to consider some of the disadvantages of raised beds. If you have decided to construct your own, check out this step-by-step guide on how to build a raised bed.
Guidelines to Building a Raised Bed
Step 1: Planning
Decide where you want your raised bed to go. Find a spot that gets the most sun and then start taking down some measurements. I recommend a bed no wider than 4 feet to easily manage and harvest crops. The length of the bed is more negotiable, but the depth should be at least 6-12 inches to allow proper rooting. If building on solid ground like concrete or pavement, the bed should be at least 18 inches deep.
Step 2: Choosing Materials
There is a variety of materials for raised garden beds but I stick to wood since its affordable and attractive. If you also opt for wood, make sure that they are untreated to keep your homegrown food safe from toxic chemicals. Instead, look for naturally rot-resistant wood like redwood, cedar, or douglas fir. Redwood can withstand the elements for a long time (20 years) but its pretty expensive. If you’re on a budget, go for douglas fir which can last 5-7 years.
Step 3: Prepping the Location
Placing raised beds on concrete or pavement can have drainage issues, so stick with bare ground if you can. Before constructing the bed in its permanent place, work the soil. Remove as much weed as you can, then grab a garden fork and loosen the top 6-8 inches for better drainage.
- If building directly on grass, place a weed barrier such as cardboard or newspaper.
- In case of rodent (e.g. gophers) problems, line the bottom of the bed with 1/2 inch hardware cloth.
- Try your best to level the surface if you have to place your bed on a slope.
Step 4: Building the Raised Bed
Cut the wood to your specific measurements, then use screws or nails to secure the corners. To avoid splitting the wood, drill some pilot holes. Wooden posts will also have to go in every corner to secure the raised bed. Ideally, each post should be 2 feet underground to make sure that the frames stay put.
Step 5: Fill the Bed with Soil
Use this calculator to figure out how much soil your raised bed needs. To avoid rot and slow drainage, stick with loam or sandy loam. Loam is soil composed of 40% sand, 40% silt, and 20% clay, while sandy loam is a mixture with more than 40% sand. Garden stores should carry potting soil ideal for raised beds, but I recommend ordering bulk garden soil as a cheaper option. When ordering in bulk, ask the retailer about the contents of what your getting.
Once you have purchased a soil mixture, do a quick mason jar soil test. If your mix is heavy on clay, amend it with organic matter or perlite for better drainage.
Other things to consider:
- Fill your bed with at least 6 inches of soil
- During the first watering, you may encounter a hydrophobic soil
Once you fill your bed with soil, you’re ready to start planting. Check out my How to Grow blog posts to help you decide which crops to grow.