Build Raised Garden Bed From Pallets: Markings and Safety
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Updated 19 October 2026 | Author: Editorial team, homelycapers.com
To build raised garden bed from pallets safely, start with the markings on the wood, not the look of the boards. Pallets are cheap and easy to take apart, but the chemical history of a pallet decides whether it belongs around vegetables. The sources we downloaded from university extension and library pages give a clear check: read the treatment codes, reject pallets with unknown or risky treatments, and line the soil side when in doubt. This guide explains the codes, the older treatments to avoid, the liner step, and the soil arithmetic for a bed of any size.
Quick answer
- Read the stamp before you cut. Heat-treated pallets carry HT, kiln-dried pallets carry KD, and methyl bromide pallets carry MB. The University of Washington Libraries says that “Pallets treated with methyl bromide bear the initials MB.”
- Do not use MB pallets. The Ask Extension answer from the University of Maryland HGIC says to dispose of them at a hazardous waste facility.
- Avoid older treatments. The University of Maryland Extension says to avoid CCA, creosote and Penta-treated lumber, and notes CCA-treated wood is no longer available for residential use as of 2004.
- Line the soil side. The same Maryland guide suggests a heavy plastic liner between the treated wood frame and the soil, allowing for drainage, as a precaution when the treatment is uncertain.
Start with the markings
Every pallet should be read before it becomes a bed wall. The codes stamped on the wood tell you how the pallet was treated. The Ask Extension answer lists the common codes as HT for heat treated, DB for debarked, KD for kiln dried and MB for methyl bromide, and it says a pallet can carry a combination of them. A pallet may also show a numerical code and a logo that identify the inspector.
The codes lead to different decisions. The University of Washington Libraries says that “Heat-treated pallets bear the initials HT (or sometimes KD for kiln dried) near the IPPC logo.” A heat-treated pallet is the usual first choice for a garden bed. Kiln-dried pallets are also marked for a reason. The Ask Extension answer says “Kiln-dried pallets have the moisture in the wood reduced to a level below 19%,” which describes drying, not chemical treatment. The same answer also points out that the kilns do not reach the same temperatures as heat treatment, so KD and HT are not interchangeable in every case.
Methyl bromide is the code to refuse. The University of Washington page says pallets treated with methyl bromide bear the initials MB, and the Ask Extension answer explains that methyl bromide is a pesticide used to treat pallets. Its advice on what to do with those pallets is direct: dispose of them at a hazardous waste facility.
The table below summarizes the codes and what each source says about using them. It is a reading guide, not a substitute for checking the pallet you have in hand.
| Mark on the pallet | What the sources say | Use for a vegetable bed? |
|---|---|---|
| HT (heat treated) | Heat-treated pallets bear HT, or sometimes KD, near the IPPC logo (UW Libraries) | Usually the first choice, with a liner as a precaution |
| KD (kiln dried) | Moisture is reduced to below 19% (Ask Extension) | Acceptable as a drying mark, with the same origin check |
| MB (methyl bromide) | Methyl bromide is a pesticide; dispose of at a hazardous waste facility (Ask Extension) | No |
| Unmarked | The Ask Extension answer says an unmarked pallet may be safe to use | Only if you know its history, and a liner is wise |
| CCA or older treatment | CCA is no longer available for residential use as of 2004 (UMD Extension) | No |
Unmarked pallets and older wood
The hardest case is the pallet with no marks at all. The Ask Extension answer says that “If a pallet is unmarked, it may be safe to use,” but that sentence is a conditional, not a promise. It depends on where the pallet came from and what it carried. The University of Washington Libraries makes the same point from a different angle: the color of the wood is not a reliable indicator of treatment, especially with older wood.
Older treatments are the bigger concern. The University of Maryland Extension says “Avoid using older types of wood treatments such as CCA, creosote, and Penta-treated lumber.” The Oregon State Ask Extension answer says that the primary concern with treated wood in raised beds has been arsenic in CCA-treated lumber. It also says that CCA-treated material is unlikely to be found in home centers because its use was restricted by the EPA in 2004. A pallet that looks old, or that is stained, should be treated with more caution than a newer heat-treated one.
The University of Washington page gives a useful reminder about how common older treatments were. It cites a 2008 Australian study that examined pallets and found one percent contained CCA. One percent is a small share, but it is a share, and you cannot see it in the wood. That is the reason the sources ask you to check the markings and to choose a liner when the origin is unknown.
Pressure-treated lumber and the soil
Some gardeners use pressure-treated lumber rather than pallets, and the sources speak to that too. The Oregon State Ask Extension answer says the safety of pressure-treated lumber for raised beds has been examined by several researchers, and that the main concern is arsenic from CCA-treated wood. The University of Maryland Extension reports Oregon State research showing that pressure-treated lumber does increase soil copper concentrations, but only within 1 inch of the raised-bed edge.
That finding matters for placement. A bed with a treated frame can have a small increase in copper near the edge, so the soil near the wall is the part to watch. The same Maryland guidance lists several ways to reduce the risk. It suggests painting the wood with exterior latex paint, lining the frame, choosing a decay-resistant wood, or using non-wood materials such as stone or brick. It also suggests a decay-resistant species, and names cedar, black cherry, oak, black locust, Osage orange and redwood.
The liner is the most practical step for a pallet bed. The University of Maryland Extension advises that you “Apply a heavy plastic liner between the treated wood frame and your garden soil, allowing for soil drainage.” The point is to keep the soil in contact with the liner rather than the wood, while still letting water move out of the bed. Choose a liner that drains and that you can staple to the inside of the frame. Do not seal the bottom completely, because the soil needs to drain.
Building the bed
Choose the location and the frame first. The sources we downloaded do not give a set size for a pallet bed, so the dimensions are yours to choose. What they do support is the materials check and the liner. Assemble the frame so the marked side faces the outside of the bed and the liner covers the inside walls. Keep the bed frame level and firm, so the soil does not push the wood apart.
Soil volume is simple arithmetic, and it is the step most people underestimate. The volume of a rectangular bed is length times width times depth. Use feet for all three measures and you get cubic feet. A 4 by 8 foot bed filled 8 inches deep, which is two-thirds of a foot, holds 4 × 8 × 0.667 = 21.3 cubic feet of soil. Divide by 27 to get cubic yards: 21.3 ÷ 27 = 0.79 cubic yards. Plan for settling by adding a little more soil at the top, and check the depth after the first watering.
The University of Maryland HGIC answer on pallets is a useful check at this stage. It treats the markings as the first decision, so that a pallet that does not pass the check never reaches the building step. A bed built from a marked, heat-treated pallet with a liner fits what the sources recommend. A bed built from an unknown pallet with no liner is the case where the sources give the most caution.
How we chose
We chose the four pallet sources because they answer the marking question directly, and because two of them are university extension answers and two are extension or library guides on the same question. We used their quotes to build the table and the decision steps. We did not rank pallet suppliers, pallet sizes or building kits. The sources differ on how serious the risk from modern treated wood is, so this guide reports that difference rather than settling it. The safety rule we follow is the one the sources share: check the marks, avoid MB and older treatments, and line the bed when the origin is unknown.
What we could not verify
The sources do not state a standard pallet size, and none of them gives a measured leaching level for modern heat-treated pallets. The University of Washington page says the color of old wood is not a reliable guide, but it does not give a check that proves a pallet is safe. The Ask Extension answer says unmarked pallets may be safe, and does not say how to confirm the origin of a pallet picked up from a shop or a pile. We also did not find a source on how long the liner lasts before it needs replacing, so plan for inspection each season.
Checklist before you build
Use this list before you cut or assemble anything. Each step comes from one of the pallet sources in this guide.
- Read every stamp on every pallet. The Ask Extension answer lists HT, DB, KD and MB codes, and a pallet can carry more than one.
- Set aside any pallet marked MB. The Ask Extension answer says to dispose of these at a hazardous waste facility rather than use them in a vegetable garden.
- Treat unmarked pallets with caution. The Ask Extension answer says an unmarked pallet may be safe, which is a conditional statement. Use one only if you know where it came from.
- Avoid older treatments. The University of Maryland Extension advises avoiding CCA, creosote and Penta-treated lumber.
- Consider decay-resistant wood or a liner. The Maryland guide lists cedar, black cherry, oak, black locust, Osage orange and redwood as options, and suggests a heavy plastic liner between the frame and the soil.
- Calculate the soil before you fill. Length times width times depth, in feet, gives cubic feet. Divide by 27 for cubic yards.
FAQ
Are heat-treated pallets safe for vegetables?
The sources treat heat-treated pallets, marked HT, as the usual first choice. The University of Washington Libraries describes the HT mark. A liner between the wood and the soil remains a sensible precaution, as the University of Maryland Extension advises.
What does MB mean on a pallet?
MB is the mark for methyl bromide, a pesticide used to treat pallets. The Ask Extension answer says to dispose of these pallets at a hazardous waste facility and not to use them in a vegetable garden.
Can I use a pallet with no markings?
The Ask Extension answer says an unmarked pallet may be safe to use, but the sources do not promise it is. Use an unmarked pallet only if you know where it came from, and add a heavy plastic liner between the wood and the soil.
Is pressure-treated lumber better than a pallet?
The sources do not rank them as a pair. The Oregon State Ask Extension answer and the University of Maryland Extension both say pressure-treated lumber raises soil copper only within about 1 inch of the bed edge, and older CCA-treated wood is the main concern. Check the treatment on any wood you use, and line the frame.
How much soil do I need for a 4 by 8 foot bed?
Multiply length, width and depth in feet, then divide by 27 for cubic yards. For a bed 8 inches deep, the volume is 4 × 8 × 0.667 = 21.3 cubic feet, or 0.79 cubic yards. Add a little extra for settling.
Related reading
For how much soil a raised bed needs and what mix to use, see our guide to how much soil a raised bed garden needs. For filling a finished bed, see how to fill raised beds.
Bottom line
Build raised garden bed from pallets only when the markings are clear, the pallet is heat treated or kiln dried, and it has no methyl bromide or older chemical history. Line the soil side with a heavy plastic liner that still lets the bed drain, and measure the soil by length, width and depth.
Sources
- Ask Extension, “Planting in Pallets” (University of Maryland Extension HGIC, #899120): the HT, DB, KD and MB codes, unmarked pallets, the MB disposal advice and the kiln moisture level.
- University of Washington Libraries, “Safety of Wooden Pallets for Vegetable Gardens”: the HT and MB initials, the 2008 CCA study, and the caution that color is not a reliable indicator.
- University of Maryland Extension, “Safety of materials used in building raised beds”: older treatments to avoid, the CCA date, decay-resistant woods, the heavy plastic liner, and the copper finding.
- Oregon State University Extension, “Raised bed lumber, pressure treated safe?” (Ask Extension): the research review on pressure-treated lumber, the concern about CCA and the 2004 EPA restriction.
