How to Build Raised Beds Cheaply – DIY Guide
Build raised beds cheaply by using reclaimed timber, scaffold boards, or sleepers cut to length. A basic 1.2 x 2.4 m bed can be built for under £30 using second-hand materials, four corner posts, and basic fixings. No specialist tools required.
Mark Out and Cut Your Boards
Decide on your bed dimensions before cutting anything — 1.2 m wide is the standard recommendation so you can reach the centre from either side without standing in the bed. Length can be whatever suits your space, though 2.4 m is practical because it makes efficient use of standard board lengths. Use a tape measure and carpenter’s square to mark your cuts clearly, then cut to length with a hand saw or circular saw. For a double-height bed (recommended for root vegetables), you will need two boards stacked per side. Cut your corner posts to a length 200–300 mm longer than the board height so they can be driven into the ground for stability.
Assemble the Frame on Flat Ground
Lay out all four sides on a flat surface before fixing anything together. Position a corner post at each internal corner so the boards butt up against them, then drill pilot holes and drive 75–100 mm galvanised screws through the boards into the corner posts. Galvanised fixings are essential — standard zinc-plated screws will rust within a season when buried in damp soil. Use a carpenter’s square to check each corner is at 90 degrees as you go, and check the assembled frame is square by measuring diagonals — they should be equal. If you are building a longer bed (over 1.5 m), fit an additional central support post on each long side to prevent the boards bowing outward once filled.
Position and Level the Bed
Choose a spot that receives at least six hours of direct sunlight per day for most vegetables, or partial shade for salad crops and herbs. Use a string line to mark the footprint, then remove any turf or perennial weeds within the area. Place the assembled frame in position and use a spirit level across the top edges in both directions — if the ground slopes, pack under the lower side with soil or gravel until the frame sits level. Drive the corner posts into the ground using a mallet or club hammer, checking level again after each post is set. A level bed ensures water distributes evenly and soil does not wash to one end. For more ideas on getting the most from your outdoor space, browse our Garden Guide.
Line the Base and Fill the Bed
Lay weed-suppressing membrane across the base of the bed and up the inside edges by about 50 mm to prevent weeds pushing through from below while still allowing drainage. A thin layer of gravel or sharp sand beneath the membrane improves drainage on heavy clay soils. Filling a raised bed cheaply is its own subject — a mix of topsoil, homemade compost, and well-rotted manure is the most cost-effective approach. Avoid filling entirely with bought compost as it compacts quickly and is expensive. Fill to within 25–50 mm of the top to allow for watering without overflow. Firm gently by hand rather than compacting with your feet.
Treat the Timber and Finish Off
Apply a plant-safe, water-based wood preservative to all external surfaces of the timber once the bed is in place and filled. Do not apply preservative to internal surfaces that will be in contact with growing medium. Two coats on the outside will significantly extend the life of the timber — untreated softwood in direct ground contact may last only two to three seasons, whereas treated timber can last five to ten years. Reapply preservative each autumn before the wet season. If you want a neater finish, the top edges of the boards can be lightly sanded to remove splinters. Your bed is now ready to plant — seeding and establishing bare ground nearby at the same time makes efficient use of the day.
Frequently Asked Questions
What is the cheapest material for building a raised bed?
Reclaimed scaffold boards are consistently the cheapest option — they are thick, durable, and often available free or very cheaply from scaffolding companies and online marketplaces. Old fence boards and sawn structural timber offcuts are also good low-cost choices, provided they have not been treated with chemicals unsafe for edible growing.
How deep does a raised bed need to be?
A minimum of 200 mm depth suits most salad crops, herbs, and shallow-rooted vegetables. For root vegetables such as carrots and parsnips, aim for 300–400 mm. One scaffold board laid flat gives approximately 225 mm, which covers the majority of common vegetable crops.
Do I need to remove the grass before building a raised bed?
You do not need to dig the turf out — a layer of cardboard or weed-suppressing membrane laid directly over short grass is sufficient for most situations. The grass will die off beneath and eventually break down into organic matter. Laying the membrane before filling prevents persistent weeds such as couch grass pushing through from below. For more on managing the surrounding lawn, our guide on how to feed and weed a lawn is worth reading.
How long will a cheap timber raised bed last?
Untreated softwood in ground contact typically lasts two to four seasons before the base begins to rot. Applying a plant-safe wood preservative to external surfaces each year can extend this to five to ten years. Hardwood and oak sleepers last considerably longer but cost significantly more upfront.
Can I use old pallets to build a raised bed cheaply?
Pallets marked HT (heat-treated) are safe to use in the garden. Pallets marked MB (methyl bromide) have been chemically treated and should never be used near edible crops. Always check the pallet stamp before using — if you cannot identify the treatment mark, do not risk it for a vegetable bed.
Before filling, staple a double layer of weed-suppressing membrane to the inside faces of the timber boards from soil level down — not just the base. This stops moisture wicking directly into the wood end-grain from the growing medium, which is where rot starts fastest, and can double the working life of cheap softwood boards.
Sources
- RHS — Raised beds: how to make and fill them — rhs.org.uk
- Which? — How to build a raised bed — which.co.uk
- HSE — Wood preservatives: safety in the garden — hse.gov.uk
This guide is for general information only. Always work safely and follow manufacturer instructions. DIYnut accepts no liability for injury or damage arising from DIY work.
