Heat treated vs kiln dried pallets: what the stamps mean
Heat treatment (HT) heats the wood core to at least 56 °C for 30 minutes to meet ISPM 15 for export. Kiln drying (KD) lowers moisture content, typically to 19% or less, to reduce mold, shrinkage and weight. Choose HT for international shipping, KD for moisture control, and KD-HT when you need both.
Heat treatment and kiln drying both use heat, and both show up as stamps on pallets, so they are easily confused. They answer different questions. HT answers "is this wood free of live pests, so it can cross a border?" KD answers "how much water is in this wood?"
Side-by-side comparison
| Heat treated (HT) | Kiln dried (KD) | |
|---|---|---|
| Purpose | Kill insects and pests in solid wood packaging | Reduce moisture content |
| Requirement | ISPM 15 treatment schedule | Target moisture content, often 19% or less |
| Process spec | Wood core at least 56 °C (133 °F) for 30 continuous minutes | Kiln schedule until the target moisture is reached |
| Mark | IPPC mark with country code, producer number and "HT" | "KD" or "KD19" style lumber stamp; not an export mark |
| Required for | Most international shipments of wood pallets | Some customer specs (for example containerized shipments), mold-sensitive goods |
| Effect on moisture | Some drying, no guaranteed level | Controlled, measured level |
| Mold resistance | Not guaranteed | Much better while it stays dry |
| Weight | Similar to untreated | Lighter (less water) |
| Typical added cost | About $1–3 per pallet (est.) | Usually more than HT (longer process) |
What heat treatment does
ISPM 15, the international standard for wood packaging, lists approved treatments. The common one in North America is heat treatment: the core of the thickest piece reaches at least 56 °C for 30 continuous minutes. The pallet or lumber is then marked with the IPPC mark: the IPPC symbol, the country code, the producer or facility number assigned under the national program, and the treatment code HT. Dielectric heating (DH) is another approved method. See ISPM 15 and heat-treated pallets.
HT is about biosecurity. It says nothing about how dry the wood is. A pallet built from green lumber and then heat treated can still have high moisture content, and it can grow mold in a container.
What kiln drying does
Kiln drying removes water in a controlled kiln until the wood reaches a target moisture content. Dry wood is lighter, more dimensionally stable (it shrinks before assembly, not after), holds fasteners better over time, and resists mold and stain as long as it stays dry. Some retailers and shippers set moisture limits: for example, requirements for containerized shipments of less than 19% moisture content appear in retailer vendor specifications.
KD is not a phytosanitary treatment unless the kiln schedule also meets the HT requirement and the wood is marked accordingly. The combined stamp is KD-HT.
Cost
Heat treatment adds roughly $1–3 per pallet in 2026 US estimates, depending on the plant, chamber size, volume and whether lumber or whole pallets are treated. Kiln drying to a moisture target takes longer and uses more energy, so it usually costs more than HT alone, and it is often done at the lumber stage. Many pallet shops buy KD-HT lumber so both requirements are met without a separate step. See pallet cost.
How to check a pallet
Look for the IPPC mark on at least two opposite sides: the IPPC symbol, the two-letter country code, the facility number and the treatment code (HT, or DH for dielectric heating). A "KD" or "KD19" stamp alone, or a lumber grade stamp, does not show ISPM 15 compliance. To check moisture, use a pin moisture meter on several boards and stringers or blocks, taking readings below the surface and away from ends; readings above about 19–20% suggest the wood was not dried or has picked up water since. For incoming inspection routines, see pallet inspection.
Repairs and re-marking
Repaired or remanufactured pallets that go overseas must be re-treated and re-marked under ISPM 15, with old marks removed. A KD claim on a repaired pallet only applies to components that were dried. See pallet stamps and markings.
When to choose each
Choose HT when: the pallet will cross an international border that enforces ISPM 15 (most do); a customer or importer requires the IPPC mark.
Choose KD when: mold, stain or weight matter (food, pharma, containers, long storage); the customer specifies a moisture limit; you want dimensional stability.
Choose KD-HT when: you export mold-sensitive goods, especially in ocean containers.
Consider non-wood when treatment is a burden: plastic, presswood, metal and paper pallets are outside ISPM 15. See plastic vs wood and pallet mold.
On an RFQ, state both requirements separately: "ISPM 15 HT, IPPC marked on two opposite sides" and "moisture content at or below 19% at shipment", with how you will check it.
Frequently asked questions
Is a kiln dried pallet ISPM 15 compliant?
Only if it was also heat treated to the ISPM 15 schedule and carries the IPPC mark with the HT code. A KD stamp on its own is not export compliance.
Does heat treatment dry the wood?
Somewhat, but not to a set moisture content. The HT schedule is about core temperature and time, so an HT pallet can still be wet enough to mold.
How much does heat treatment add to pallet cost?
Roughly $1–3 per pallet in 2026 US estimates, depending on the plant, volume and pallet size. Kiln drying to a moisture target usually costs more because it takes longer.
What does KD-HT mean on a stamp?
The wood was kiln dried and the process also met the ISPM 15 heat treatment schedule. It is common in kiln-dried lumber that is later used for pallets.
Sources and references
Related
- GuidesHeat-treated pallets (HT): what they are, when you need them, and costA heat-treated (HT) pallet's wood core was held at 56 °C (133 °F) for 30 minutes under ISPM 15, then stamped with the IPPC mark and HT. Most countries require it on wood pallets crossing their border. It adds roughly $1–3 per pallet (2026 US estimate) and kills pests; it does not dry the wood.
- StandardsISPM 15: the wood packaging standard for international shippingISPM 15 is the IPPC standard requiring solid-wood packaging, including pallets and dunnage, to be debarked, treated (HT, DH, MB or SF) and marked before crossing a border. Plywood, OSB, presswood, wood 6 mm thick or less, and plastic, metal and paper pallets are exempt.
- GlossaryWhat does kiln-dried mean for pallets?Kiln-dried (KD) lumber has been dried in a heated kiln to a target moisture content, most often 19% or less (KD19). Kiln drying reduces weight, shrinkage and mold risk, but a KD stamp alone does not show ISPM 15 compliance.
- GlossaryWhat is heat treatment (HT) for pallets?Heat treatment (HT) is the ISPM 15 method of heating wood packaging until the whole profile of the wood, including its core, reaches at least 56 °C for 30 continuous minutes. Treated pallets carry the IPPC mark with the code HT.
- GlossaryKD-HTKD-HT indicates wood that is both kiln dried (KD), dried to a target moisture content, and heat treated (HT) to ISPM 15. Only HT is an ISPM 15 treatment code; KD describes moisture and does not by itself make a pallet export compliant.
- GlossaryMoisture content (pallet lumber)Moisture content (MC) is the weight of water in wood expressed as a percentage of the wood's oven-dry weight. Pallet specs usually call for 19% or less when dry wood is needed; green lumber is above about 28%.
- GuidesPallet mold: causes, prevention and what to do with moldy palletsPallet mold grows when wood stays above about 20% moisture in warm, still air: green pallets in containers, wrapped loads or covered yards. The fix is dry wood: specify kiln-dried pallets (19% or less), store them dry and ventilated, and check moisture before loading. HT alone does not prevent mold.
- GuidesPallet stamps and markings: HT, MB, DB, KD and what they meanMost wood pallet stamps are the ISPM 15 mark: IPPC wheat symbol, country code, facility number and treatment code. HT means heat-treated, DH dielectric heating, MB methyl bromide, SF sulfuryl fluoride. DB (debarked) and KD (kiln-dried) are older or separate marks. For reuse, pick HT and avoid MB.
More in Materials
- ComparisonsPlastic vs wood pallets: cost, strength and when to use eachChoose wood when you need the lowest price, a custom size, easy repair or one-way shipping. Choose plastic when pallets run in a closed loop for many trips, when hygiene and washability matter, when you need consistent dimensions for automation, or to avoid ISPM 15 treatment on exports.
- ComparisonsPresswood vs wood pallets: differences and when to use eachChoose a presswood (molded wood-fiber) pallet for one-way export and air freight: it is ISPM 15-exempt, nails-free, light and nests about 4:1 for storage. Choose a solid wood pallet when you need racking, heavy or custom loads, or pallets you will reuse and repair.
- ComparisonsMetal vs plastic pallets: steel, aluminum and plastic comparedChoose a metal pallet (steel or aluminum) for very heavy, hot, sharp or long-life loads, fire-sensitive storage, or when you need a custom fabricated size in small quantities. Choose plastic for lighter closed-loop handling, lower price, lower tare weight and standard footprints.
- ComparisonsHardwood vs softwood pallets: strength, weight and costChoose hardwood (oak, mixed eastern hardwoods) for heavy loads, rough handling and many trips: it is dense, stiff and holds nails well but is heavier. Choose softwood (southern yellow pine, SPF) for lighter, more uniform, often kiln-dried pallets. Regional supply often decides.
Last reviewed 2026-09-24. 782 words.