Raised Garden Bed from Pallets: Safety Check and Build Guide

Key Takeaways

• A pallet is only safe to grow food in only when the stamp says HT and its last load is known, because the mark records how the wood was treated and nothing about what it has carried since.
• An unmarked pallet is not an untreated pallet by definition, but it is an untraceable one, and nothing can tell you what soaked into it.
• Untreated pallet softwood in permanent contact with wet soil rots through in three to four years, so the box is a short-term structure however well it is built.
• A raised bed measuring 1.2 by 1.2 metres filled to 250mm takes around 415 litres of soil once settlement is allowed for.

I will show you how to build a raised garden bed from pallets properly, because plenty of people will anyway. But my position is plain: if you are growing anything you intend to eat, a pallet is the wrong box, and I would put the same weekend into railway sleepers or sawn treated timber. Here is why, then the build.

Are Pallets Safe to Grow Food In?

Pallets are safe to grow food in only when the treatment stamp reads HT and you know what the pallet carried on its last job.

The stamp is the easy half. A pallet that has crossed a border since 2002 carries an IPPC mark (a boxed wheat-ear logo) with a treatment code beside it. HT means heat treated, the timber held at 56°C to the core for half an hour to kill insects. Nothing chemical goes in. MB means fumigated with methyl bromide, the code the internet tells you to avoid.

Here is the bit that gets missed. Methyl bromide fumigation has been banned as a pallet treatment across the EU since March 2010. So a pallet stamped MB in a British yard is either fifteen years old or came in from outside Europe, and either way it has had a long and unknown life.

The chemical I would actually worry about is one nobody stamps for. Between 2009 and 2011 the US Food and Drug Administration traced three medicine recalls, Tylenol among them, to wooden pallets treated abroad with a fungicide called tribromophenol. Damp pallets grew mould, the mould turned it into a chemical called TBA, and the taint got into sealed bottles stacked on top. People reported nausea and vomiting. The pallet industry disputed the cause, and the fungicide is banned in Europe, but the point stands: a pallet’s history is not written on it.

On the older worry, that preservative leaches into the crop, the best test I have seen is Oregon State University’s six-year trial. They built beds from copper-treated timber, the worst case, and found copper rose in the soil only within an inch of the boards and never rose in the vegetables, across twelve crops and four seasons. A heat-treated pallet has no preservative in it to begin with. Treatment is not the risk but the cargo is.

What the HT Stamp Does Not Tell You

The HT stamp tells you how a pallet was treated at the factory, and nothing about the twenty jobs it has done since. That is the whole problem with pallets for growing food. They carry drums of chemicals, fertiliser, fish, cement, paint, animal feed. A spill soaks into bare softwood and a wash does not get it back out. Sanding takes off the surface, not what is in the grain.

The bacteria side is smaller but real. A US consumer group swabbed 70 wooden food pallets and found E. coli on one in ten and Listeria on three in a hundred. Small sample, but it tells you what an outdoor-stored, absorbent, well-travelled bit of timber picks up.

And ISPM 15, the standard behind the stamp, only applies to pallets crossing borders. A pallet that has spent its life inside the UK may carry no mark at all and be perfectly untreated softwood. Unmarked does not mean unsafe. It means you cannot check.

Which Pallets to Take, and Which to Leave

Take a pallet only if all of the following are true:

• Stamped HT or DH, with a legible IPPC mark
• Its last load is known to you (a garden centre, a builders’ merchant, a food shop you can ask)
• Dry, unstained, no smell of oil, chemical or rot
• Plain timber, not painted blue or red (those belong to pallet pools like CHEP and LPR and are not yours to take)

Walk away from:

• Anything stamped MB
• Anything with no stamp and no known history
• Any board that is dark-stained, greasy, or smells of anything but wood
• Pallets from a yard that handles chemicals, whatever the stamp says

Taking a Pallet Apart, or Leaving It Whole

A pallet comes apart fastest with a reciprocating saw run between the boards to cut the nails, and it stays together strongest if you leave it whole.

Prising boards off with a crowbar splits about one in three, because the ring-shank nails hold better than the softwood does. A reciprocating saw with a metal blade slid between board and bearer cuts each nail in a second and the boards come off clean. Gloves and eye protection: pallet timber splinters and the nail ends are sharp.

The alternative is to stand whole pallets on edge as the four walls. Faster, stiffer, and the corner blocks become posts. The cost is a 14cm-thick wall with gaps between every slat, which is what the lining section is about.

Building the Bed

A pallet raised bed goes up in an afternoon with a drill, long screws and a spirit level. This is the whole-pallet method; the dismantled-board method is the same shape with more screws.

1. Level the ground. Scrape it flat and check with a spirit level on a board. A bed on a slope pushes its soil weight into the downhill wall.
2. Stand four pallets on edge to form the rectangle, deck boards facing out. Set each corner post on a paving slab or a brick so the end grain is not sitting in mud.
3. Screw the corners through the pallet blocks, three 120mm exterior screws per corner, driven into the block rather than the slats. Screws in slats pull out within a season.
4. Brace the long walls. Anything over 1.2m needs a batten screwed across the inside at half height, or the wet soil bows the wall out by spring.
5. Fill the gaps. Screw spare slats across the inside of each wall to close the slots, or the soil pushes through the liner and out.
6. Sand the top edges. Two minutes with a mouse sander saves a summer of splinters.

Do not oil or seal the inside face. The next two sections say why.

How Deep Does a Raised Bed Need to Be?

A raised bed for vegetables needs 200 to 300mm of soil; a whole pallet on edge gives 800mm, twice the soil bill for no gain.

• Salads, herbs, strawberries: 200mm is plenty
• Beans, brassicas, courgettes: 250mm
• Carrots, parsnips, potatoes: 300mm, and not in a freshly filled bed (they fork in fresh organic matter)
• A pallet cut down to two boards high gives roughly 250mm, which is the depth I would build to

Should You Line a Pallet Raised Bed?

A pallet raised bed should be lined on the walls with non-woven weed fabric, stapled every 10cm, and left open at the bottom.

The lining is doing one job, and it is not weed control. It is separation: keeping the soil inside a wall full of gaps, and the boards out of wet soil. Non-woven fabric does that and still lets water out sideways. Polythene holds water against the timber and rots it faster.

Leave the base open to the ground. Worms come up, water goes down, and the bed behaves like soil rather than a pot. On a patio, whether it needs a base depends on what the slabs are laid on, and I have covered that in raised beds on a patio. For a bed on a concrete yard or an old garage base, see my guide to a raised bed on concrete. Clients used to ask me whether the liner made a pallet safe for food. It does not. A liner keeps soil off the wood, not what was in the wood off the soil.

What to Fill a Raised Bed With, and How Much You Need

A raised bed is filled with a screened topsoil to within 30mm of the top, and the volume is length times width times depth plus 10 to 20% for settlement. This is the section that catches everyone. The pallets were free. The soil is not.

Those figures include 15% for settlement. A new bed drops that much in its first season, so fill it proud rather than level.

What goes in matters as much as how much. I fill with our vegetable topsoil, a 10mm screened loam with the organic matter already blended in, peat-free and manure-free. Manure-free is the one I care about, because the commonest way to poison a vegetable bed in this country is not a pallet, it is aminopyralid weedkiller arriving inside somebody else’s muck. If you would rather build the mix yourself, the Compost Mulch Range compares what we stock for that. Odd-shaped beds go through the topsoil calculator.

The layering trick you see everywhere (twigs, leaves, turf, then soil) works, but the bed sinks 30 to 40% in year one as it rots down. A bed filled with compost alone sinks the same way, which is why I set out the difference between topsoil and compost here.

How Long Will a Pallet Raised Bed Last?

A pallet raised bed lasts three to four years before the boards touching soil go soft, a season or two longer if lined.

Untreated pine in wet soil rots in three to four years, and pallet boards are 20mm softwood, so they sit at the short end of that. Oregon State’s untreated beds, built from 50mm boards, had the lower half rotted through by year six. A pallet board has less than half that thickness to lose.

You can slow it, but not the way most people try. Boiled linseed oil is raw linseed oil with cobalt and manganese driers added, and the tin’s own safety sheet says so. Raw linseed oil has none of that and is safe near food, but it takes weeks to cure and wants redoing yearly. Either way, oily rags go in a sealed metal tin. They can catch fire on their own.

My advice is the plainer one. Accept the lifespan, keep the boards on slabs, line the walls, and treat it as a three-year box. A bed that outlasts the fruit bushes is a sleeper bed, and that is a different build.

Next Steps

If you have read this far and still want the pallet bed, build it well and enjoy it for the seasons it gives you. Fill it with a topsoil made for growing food rather than whatever is cheapest, because the soil is the part that actually feeds you. We stock a screened, peat-free vegetable topsoil in 25 litre bags and 700 litre bulk bags, plus the non-woven weed fabric for the lining, delivered to the kerb.

If you would rather talk the soil for your raised bed through with a person, ring Outdoor Aggregates on 0330 043 7585. The office is open 7am to 7pm, seven days a week.

Have you ever built a raised bed from pallets? Which pallets did you use, and how many seasons did the boards last? Would love to hear how it held up in the comments.

FAQs

Do pallets make good raised garden beds?

Pallets make a cheap, quick raised bed but not a good one for food, because the timber’s history is unknowable and the boards rot in three to four years. For flowers they are fine.

What are the disadvantages of using pallets for raised beds?

Pallet raised beds have four drawbacks: an unknown cargo history, softwood that rots in a few years, gaps in every wall that need filling and lining, and a soil bill that usually costs more than new timber would have.

Are unmarked pallets safe for a vegetable garden?

Unmarked pallets are not safe for a vegetable garden, not because they are treated but because nothing about them can be checked. A pallet that never left the UK needs no mark, so unmarked tells you nothing either way.

What do you put in the bottom of a raised garden bed?

The bottom of a raised garden bed on soil is left open, with cardboard laid on the grass to kill it off. A layer of twigs or rubble adds drainage the bed does not need and makes it sink further in year one.

What is the cheapest way to build a raised bed?

The cheapest raised bed is a mounded bed with no walls, soil heaped 200mm and edged with a spade. Where walls are wanted, sawn treated timber costs more than pallets but lasts three times as long, so it is cheaper per year.