The soil around a newly built house has usually been driven over by trucks, scraped, filled and graded. It can be hard enough that a shovel bounces. Raised beds get around that: instead of fixing the whole yard before you can grow anything, you build a few boxes, fill them with good soil and plant the same spring.
University of Minnesota Extension lists compacted soil in housing developments as one of the main reasons to garden in raised beds, along with soil that warms earlier in spring and fewer problems with stubborn weeds.[1] Here is how to size them, fill them and keep the cost sensible.
Key takeaways
- Make beds narrow enough to reach the middle without stepping in; walking on the soil compacts it.
- Boards of 6 feet or less are less likely to warp than long ones.
- Fill with about 1/2 to 2/3 topsoil and 1/2 to 1/3 plant-based compost, bought in bulk if you can.
- Avoid old lumber and railroad ties; CCA-treated wood can leach arsenic into vegetables.
Pick the sunniest spot near a tap
Tomatoes, peppers and eggplants need at least 6 to 8 hours of direct sun a day. If your best spot only gets a few hours, you can still grow lettuce, kale, radishes and other greens.[1] Put the beds where a hose reaches easily. Raised beds dry out faster than ground soil, and the taller the bed, the more often it needs water.[1]
How big to make each bed
Width is set by your arm. You should be able to reach the center comfortably from the side, so you never need to step into the bed.[1] For most adults that means about 4 feet wide if you can reach from both sides, less if the bed is against a fence.
Height is less important than people think. Extension says most gardeners don't need beds more than a few inches high, though one or two feet helps on very hot sites such as pavement, and about 27 inches is comfortable for wheelchair users.[1] Several short beds are better than one long one: shorter boards warp less, and separate beds make crop rotation easier.[1]
Choosing the sides
Wood is the cheapest and easiest. Cedar and hemlock cost more than pine or fir but last much longer. Galvanized steel costs more again, and Extension notes it resists rust for upwards of 50 years.[1]
Skip old and arsenic-treated wood
Railroad ties and lumber treated with chromated copper arsenate (CCA) can leach arsenic into food crops. Newer treatments use copper instead; if you use treated wood, choose lumber rated for ground contact and consider lining the inside faces. Extension also warns that some prefabricated metal beds sold online have been found to contain lead.[1]
Filling it: the part that costs the most
Extension recommends roughly 1/2 to 2/3 topsoil and 1/2 to 1/3 plant-based compost. Potting soil dries out too quickly for raised beds, and too much compost can repel water once it dries.[1] Kill the grass underneath and loosen the soil before filling; a barrier between the bed and the ground is usually unnecessary and can stunt roots.[1]
Work out the volume before you shop. A bed 4 feet by 8 feet filled 1 foot deep holds 32 cubic feet, a little over 1 cubic yard. Two or three beds that size are where bulk delivery by the yard, which Extension says is generally much cheaper than bags, starts to pay off.[1]
What it adds up to
HomeGuide puts a 4 by 8 foot raised bed kit at $150 to $480, and a custom-built 5 by 12 foot bed at $1,200 to $4,000 installed.[2] The difference is mostly labor and material. If you build it yourself from untreated lumber, the soil often costs more than the box.
Laying out the paths
The space between beds is part of the garden too. Make at least one path wide enough for a wheelbarrow, because you will move compost and mulch every year. Narrower paths are fine elsewhere, as long as you can kneel comfortably. Grass paths look tidy but need mowing and edging, and the grass creeps into the beds. Wood chips or bark mulch over cardboard are cheap, easy to walk on and smother weeds.
If you can, run long beds roughly north to south so both sides get similar sun. Put tall crops such as staked tomatoes or pole beans at the north end so they don’t shade everything else.
A sensible first season
New gardeners usually plant too much of everything at once and then harvest twenty heads of lettuce in the same week. Start with a few crops you actually eat, and plant quick ones like lettuce, radishes and spinach in small batches every couple of weeks so the harvest is spread out.
Leave room for two or three big summer plants, such as a tomato, a zucchini or a pepper, and give them more space than the seedling looks like it needs. Your local Extension office publishes planting dates for your area, which is the most reliable guide to when each crop goes in.
Watering without the daily chore
Raised beds dry out faster than the ground, so watering is the job that decides whether the garden survives July. A soaker hose or drip line snaked through each bed and connected to an inexpensive timer at the tap takes care of most of it, and it puts water at the roots instead of on the leaves. A few inches of straw or shredded leaves on top of the soil slows evaporation further.
To check whether a bed needs water, push a finger into the soil. If it is dry a couple of inches down, water deeply rather than giving it a quick splash.
Keeping the beds going year after year
Soil in a raised bed settles and breaks down, so expect the level to drop a little each year. Top it up with a layer of compost in spring or fall rather than replacing the soil. Covering beds over winter with shredded leaves protects the surface and feeds it as the leaves rot.
Move crop families to a different bed each year where you can, especially tomatoes and their relatives, which share pests and diseases. This is where several small beds earn their keep: rotation is easy when each bed is its own unit.
Plug your house size, land price and quotes into the free calculator. It uses the same NAHB 2024 averages as this guide.
Frequently asked questions
How deep should a raised garden bed be?
University of Minnesota Extension says most gardeners do not need beds more than a few inches above the ground, though 1 to 2 feet helps on very hot sites and about 27 inches suits wheelchair users.
What soil should I put in a raised bed?
About 1/2 to 2/3 topsoil mixed with 1/2 to 1/3 plant-based compost. Potting soil dries out too quickly for beds.
Is pressure-treated wood safe for vegetable beds?
Avoid old lumber and CCA-treated wood, which can leach arsenic. Newer copper-based treatments are used today; choose ground-contact lumber and consider lining the beds.
How far apart should raised beds be?
Leave at least one path wide enough for a wheelbarrow, and enough room elsewhere to kneel comfortably. Mulch paths are cheaper and easier to maintain than grass.
Do I need to replace raised bed soil every year?
No. The soil settles and breaks down, so top it up with compost each year and rotate crops between beds instead of replacing it.
Should I put anything under a raised garden bed?
Usually nothing but loosened soil. Kill the grass first, for example by covering it or digging it out. A solid barrier is rarely needed and can limit roots; hardware cloth is the exception where burrowing animals are a problem.
Sources
- University of Minnesota Extension, "Raised bed gardens" Verified
- HomeGuide, "How much does a flower bed or raised garden bed cost?", December 23, 2025 Verified
Figures last checked October 19, 2026. National averages are a planning guide, not a quote. See our editorial policy and data sources.
