Calculate exactly how much lumber, screws, and soil you need to build raised garden beds. Get a complete materials list and cost estimate.
Raised garden beds are one of the best investments a Canadian gardener can make. They warm up faster in spring (critical when you're trying to extend a short growing season), drain better than compacted in-ground soil, and let you control your soil mix completely. For gardeners dealing with heavy clay soil in Alberta, rocky ground in BC, or shallow topsoil on the Prairies, a raised bed is often the only practical way to grow a productive vegetable garden.
The most common mistake is underestimating materials — especially soil. A single 4x8x12-inch raised bed needs 32 cubic feet of soil, which is far more than most first-time builders expect. This calculator gives you an exact shopping list so you don't make two trips to the hardware store.
A 4x8 foot raised bed that is 12 inches deep needs 32 cubic feet of soil, which is about 1.2 cubic yards or roughly 21 bags of bagged soil (1.5 cubic feet per bag). At 6 inches deep it needs 16 cubic feet (11 bags). At 24 inches deep you'll need 64 cubic feet — at that volume it's much cheaper to order bulk soil by the yard rather than buying bags. Use our calculator above to get the exact numbers for your specific dimensions.
Cedar is the best choice for Canadian raised beds. It's naturally rot-resistant, weathers beautifully, and contains no chemicals that could leach into your food. Untreated cedar typically lasts 10–15 years. Pressure-treated pine (rated for ground contact) is a more affordable option and modern treatments are considered safe for vegetable gardens. Avoid old railroad ties, creosote-treated wood, or any lumber with unknown treatments. Composite lumber lasts the longest but costs significantly more upfront.
4x8 feet is the most popular size because it maximizes growing space while keeping every part of the bed reachable from the sides without stepping in. Keep the width to 4 feet maximum (or 3 feet if you can only access from one side). Length can be anything you like. For depth, 12 inches works for most vegetables. Deeper beds (18–24 inches) are better for root vegetables like carrots and parsnips, or for raised beds built over hardscape like concrete or gravel.
The classic "Mel's Mix" for raised beds is one-third compost, one-third peat moss (or coco coir), and one-third coarse vermiculite or perlite. This creates a light, moisture-retentive, and nutrient-rich mix. For budget-conscious gardeners, a 60/30/10 mix of quality topsoil, compost, and peat moss also works well. Never use straight garden soil in a raised bed — it compacts badly and drains poorly. Add a fresh layer of compost to the top each spring to replenish nutrients.
It depends on what's underneath. If your bed sits on grass or soil, you don't need a bottom — roots will grow down, and earthworms will come up to improve your soil over time. Lay cardboard or newspaper on the grass first to suppress weeds before filling. If the bed sits on concrete, gravel, or pavers, add a layer of hardware cloth or wire mesh to deter burrowing animals like voles and gophers, then fill with soil. A weed barrier fabric is optional and somewhat controversial — it can restrict drainage over time.
A basic 4x8x12-inch raised bed built from pressure-treated pine typically costs $150–$250 CAD including lumber, screws, and soil. A cedar version runs $250–$400 CAD. The biggest variable is soil — if you buy bagged soil at retail it's expensive; ordering bulk topsoil and compost by the cubic yard from a local supplier is significantly cheaper and better for large or multiple beds. Use the cost estimator in our calculator above to get a rough total for your specific build.
Cedar is rot-resistant and chemical-free (best for vegetables). Pressure-treated pine is affordable but ensure it's rated for gardens. Avoid railroad ties or creosote-treated wood.
4x8 feet is most popular (can reach middle from both sides). Keep width under 4 feet for easy reach. Height of 12 inches works for most vegetables.
Use 3-inch deck screws (not nails). Add corner braces for strength. Drill pilot holes to prevent splitting. Consider adding a bottom wire mesh to prevent burrowing pests.
Use 60% topsoil, 30% compost, 10% peat moss or coconut coir. Mix in perlite or vermiculite for drainage. Don't use garden soil alone—it compacts too much.
Plan what to plant once your bed is built.