A raised bed is the simplest fix for the two things that make growing food hard in this part of Ontario: heavy clay that stays cold and wet into May, and soil that no one has fed for twenty years. Lift the growing space above the clay and you get soil you control, drainage you control, and a bed that warms up a week or two earlier in spring. This guide covers the sizes, materials, fill and costs we use on beds across Hamilton, Burlington and Oakville.
What size should a raised bed be?
Three numbers decide whether a bed is pleasant to use or annoying forever.
| Dimension | What to use | Why |
|---|---|---|
| Width | 4 ft, or 2 to 3 ft against a wall or fence | Most adults reach about 2 ft comfortably. Anything wider means stepping in the bed and compacting it. |
| Length | 6 to 12 ft | Lumber comes in 8, 10 and 12 ft, so those lengths waste nothing. Longer beds need a cross tie to stop the sides bowing. |
| Height | 12 to 18 in for most vegetables | 6 in suits lettuce and herbs, 12 in suits almost everything, 18 to 24 in suits carrots, parsnips and easier bending. 30 to 36 in lets you work standing or from a seat. |
| Path between beds | 18 in minimum, 24 to 36 in for a wheelbarrow | Skimping here is the single most common regret. A wheelbarrow that will not fit turns every soil delivery into bucket work. |
If the bed sits on existing lawn or clay and is 12 inches or higher, roots have plenty of room and you do not need to dig underneath. On a driveway, patio or anywhere with no soil below, go to 18 inches minimum.
How much soil does a raised bed need?
This is where budgets go wrong, because bagged soil looks cheap until you count the bags. One cubic yard is 27 cubic feet, and a 25 litre bag holds about 0.88 cubic feet.
| Bed | Depth | Cubic feet | Cubic yards | 25 L bags |
|---|---|---|---|---|
| 4 x 4 ft | 12 in | 16 | 0.6 | 18 |
| 4 x 8 ft | 6 in | 16 | 0.6 | 18 |
| 4 x 8 ft | 12 in | 32 | 1.2 | 36 |
| 4 x 8 ft | 18 in | 48 | 1.8 | 54 |
| 4 x 10 ft | 12 in | 40 | 1.5 | 45 |
| 4 x 12 ft | 18 in | 72 | 2.7 | 81 |
| Three 4 x 8 beds | 12 in | 96 | 3.6 | 108 |
In Ontario, triple mix runs about $45 to $65 per cubic yard if you load it yourself at the yard, and small delivered loads run roughly $125 for one yard, $175 for two and $235 for three. Bagged soil at garden centre prices works out to roughly double the bulk price once you have filled a 4 x 8 bed. Our mulch and topsoil calculator does the volume for any bed size.
What to build a raised bed from
| Material | Lifespan in Ontario | Notes |
|---|---|---|
| Cedar | 10 - 15 years | Naturally rot resistant, easy to cut, looks good untreated. The default for a bed you will see from the house. |
| Pressure-treated (ACQ or copper azole) | 15 - 20 years | Cheapest long-lasting option. See the safety note below. |
| Hemlock, spruce or pine | 4 - 7 years | Cheap and fine for a trial bed. It will rot from the bottom up. |
| Galvanized or corrugated steel | 20+ years | Modern look, no rot, arrives as a kit. Dries out faster, so watering matters more. |
| Composite boards | 25+ years | Most expensive, zero maintenance, needs a wood or metal frame behind it on tall beds. |
| Concrete block or armour stone | Decades | Permanent, heavy, good for terracing a slope. Costs the most to install. |
Is pressure-treated wood safe for a vegetable bed?
This is the question we get most, and the answer has changed. The treatment people worry about is CCA, which contained arsenic. It left the Canadian residential lumber market in early 2004. Everything sold to homeowners since then is ACQ or copper azole: copper based, no arsenic, and registered for use by Health Canada's Pest Management Regulatory Agency. Copper binds tightly in soil and does not travel far from the board. If you want a belt-and-braces approach, staple heavy poly to the inside faces of the boards only, never the base, so water can still drain. If you have old grey lumber from before 2004, especially with a green tint and small incision marks, do not use it for food.
Raised garden bed ideas that work here
1. The classic three-bed kitchen garden
Three 4 x 8 beds with 30 inch gravel paths between them fits into a 14 x 12 ft corner and gives enough space for a real vegetable supply: one bed for tomatoes and peppers, one for roots and greens, one for beans, squash and herbs. Rotating what goes in each bed each year cuts disease.
2. The tall accessible bed
A bed at 30 to 36 inches high lets you garden standing up or from a stool, which is the difference between a garden that gets used and one that does not. Build the bottom half as a hollow frame with a false floor at 18 inches so you are not paying to fill the whole thing with soil.
3. The L-shaped or U-shaped bed
Running beds along two or three sides of a patio turns leftover space into planting and gives the sitting area a wall of green. Keep the arms 3 ft wide if you can only reach in from one side.
4. The metal bed for a modern yard
Corrugated galvanized steel beds suit modern homes and new-build yards, and they go together in an afternoon. The outer inch of soil does get warmer against the metal in July, but the bulk of the bed does not cook. The real difference is that they drain and dry faster, so plan on a drip line.
5. Beds built into a slope
On a sloped yard, a row of beds stepping down the hill turns a mowing problem into a garden. The uphill side needs to hold back soil, so this becomes a small retaining wall job. Our retaining wall cost guide covers where that line sits.
6. Beds with a hoop cover
Two lengths of conduit or PVC bent into hoops across the bed, with row cover clipped on, buys you two to three weeks at each end of the Ontario season and keeps cabbage moths off brassicas. In April it acts as a mini greenhouse; in July swap the plastic for insect netting.
7. The cut-flower bed
A raised bed of dahlias, zinnias, cosmos and snapdragons gives you something to cut all summer and is far easier to keep tidy than a mixed border. For the ornamental beds around it, see our garden bed design guide.
8. The herb bed by the back door
A small 2 x 6 bed within ten steps of the kitchen gets used. One 30 feet down the garden does not.
Building a bed that lasts
- Pick a spot with 6+ hours of sun. Tomatoes, peppers and squash need it. Leafy greens and herbs will take 4 hours. Sun is the one thing you cannot fix later.
- Level the ground. A bed on a slope drains to one end and the soil ends up 3 inches deep at the top. Cut into the high side rather than building up the low side.
- Line the base with cardboard, not plastic. Plain corrugated cardboard smothers the grass and rots away in a season. Plastic traps water and roots.
- Add hardware cloth if you have voles. Half-inch galvanized mesh stapled across the bottom before you fill stops voles and moles coming up from below. It is a ten dollar step you cannot do later.
- Screw, do not nail, and use exterior or stainless screws. Add a cross tie or a stake at the midpoint of any side longer than 8 feet, or the boards bow outward.
- Fill in layers and water each layer so the soil settles before you plant, or you will be topping up all season.
- Mulch the surface with straw or fine bark once plants are in. Raised beds dry out faster than ground beds.
When to build and plant in Ontario
You can build and fill a bed any time the ground is not frozen, and late fall is a good time because the soil settles over winter and is ready in April. For planting, the Hamilton and Halton area sits around zone 6a, with the last spring frost usually in the first half of May and the first fall frost around mid to late October. A raised bed warms up one to two weeks ahead of ground soil, so peas, spinach, lettuce and radish can go in from early to mid April. Tomatoes, peppers, cucumbers, squash and basil wait until after the last frost date, which in practice means the Victoria Day weekend for most people. Our Ontario landscape maintenance calendar sets out the rest of the year.
Watering, because this is where beds fail
A raised bed dries faster than the ground around it, and a bed against a south wall can need water every day in July. Hand watering works until the first week you go away. A simple drip line or soaker hose on a tap timer costs under a hundred dollars and is the single best upgrade to a vegetable bed. If you already have irrigation, a drip zone can be added to it: see our irrigation system cost guide, and remember to blow the lines out in fall.
What raised beds cost
| Option | 2026 Ontario range | What it includes |
|---|---|---|
| DIY materials, 4 x 8 at 12 in, pressure-treated | $60 - $120 | Lumber and screws only |
| DIY materials, 4 x 8 at 12 in, cedar | $120 - $250 | Lumber and screws only |
| Cedar or steel kit | $200 - $500 | Flat-packed bed, no soil |
| Soil to fill a 4 x 8 at 12 in, bulk | $100 - $150 | About 1.2 cu yd delivered |
| Soil to fill the same bed, bagged | $200 - $250 | About 36 bags |
| Built and filled by a crew, 4 x 8 at 16 - 18 in | $700 - $1,500 | Cedar bed, site prep, soil, delivery |
| Three-bed kitchen garden with gravel paths | $3,000 - $6,000 | Beds, soil, path base and stone, edging |
Prices are 2026 Ontario estimates and assume reasonable access. Steel beds sit near the middle of the range and stone or block beds sit well above it.
Frequently asked questions
How deep should a raised garden bed be?
12 inches suits almost every vegetable. Use 6 inches for lettuce and herbs, 18 to 24 inches for carrots, parsnips and easier bending, and 18 inches minimum if the bed sits on a driveway or patio with no soil below.
How much soil do I need for a 4 x 8 raised bed?
32 cubic feet at 12 inches deep, which is 1.2 cubic yards or about 36 bags of 25 litres. At 18 inches deep it is 48 cubic feet, or 1.8 cubic yards.
Is pressure-treated wood safe for vegetable beds in Canada?
Yes, for lumber bought since 2004. Arsenic-based CCA left the Canadian residential market in early 2004 and today's treatments are ACQ or copper azole, copper based with no arsenic. Do not reuse old pre-2004 treated lumber for food gardens.
What is the best material for a raised bed in Ontario?
Cedar for looks and 10 to 15 years of life, galvanized steel for 20 years and a modern look, pressure-treated for the lowest cost per year. Avoid untreated pine or spruce unless you accept rebuilding in about five years.
How wide should a raised bed be?
Four feet if you can walk around both sides, two to three feet if it is against a wall or fence. Any wider and you end up standing in the bed, which compacts the soil.
Do I need to remove the grass under a raised bed?
No, not for a bed 12 inches or deeper. Lay plain cardboard over the grass first and it will smother and rot away. Do not use plastic sheeting.
When can I plant a raised bed in Hamilton or Burlington?
Peas, spinach, lettuce and radish from early to mid April, since a raised bed warms a week or two earlier than ground soil. Tomatoes, peppers, cucumbers and basil after the last frost, usually the Victoria Day weekend.
Why did my raised bed soil sink?
Fresh mixes settle 15 to 20 percent in the first season as the organic matter breaks down. Top up with an inch or two of compost each spring instead of refilling with new soil.