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Kiln-dried vs heat-treated pallets

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In short

Kiln drying (KD) removes moisture from lumber to a target, commonly 19%, to cut weight, shrinkage and mold. Heat treatment (HT) is the ISPM 15 phytosanitary treatment, holding the wood core at 56 °C for 30 minutes, and is marked with the IPPC stamp. They solve different problems, and a KD stamp alone does not make a pallet export compliant.

On this page
  1. Two different treatments
  2. What kiln drying does
  3. What heat treatment does
  4. Stamps: KD, HT and KD-HT
  5. Which one do you need?
  6. Verifying each on delivery
  7. How they appear on a spec
  8. How palletdesign.ai uses them

Two different treatments

Buyers often use "kiln dried" and "heat treated" interchangeably. They are not the same.

Kiln dried (KD) Heat treated (HT)
Purpose Lower moisture content Kill pests for international shipping
Governing rule Buyer spec (e.g. below 19%) ISPM 15
Target A moisture level, commonly 19% Wood core at 56 °C (133 °F) for 30 continuous minutes
Proof Moisture meter reading, KD stamp or certificate IPPC mark with country code, producer number and HT code
Changes weight? Yes, significantly Not necessarily to a set moisture level
Required for export? No Yes, for most destinations

What kiln drying does

Kiln drying brings lumber to a target moisture, most often 19% for pallets (often written KD19). The benefits are lighter pallets, less shrinkage after assembly, lower mold risk, and stronger, stiffer wood. It is what buyers ask for when they set a moisture limit. Costco, for example, is documented as requiring below 19% moisture for containerized shipments, and EPAL requires dry wood.

What heat treatment does

Heat treatment is one of the ISPM 15 approved treatments for wood packaging. The core of the wood must reach 56 °C and stay there for 30 minutes. Afterward the pallet carries the ISPM 15 mark: the IPPC symbol, the two-letter country code, the producer or treatment-provider number and "HT". Heat treatment is what customs inspectors look for.

Stamps: KD, HT and KD-HT

  • A KD stamp describes moisture only. It is not ISPM 15 compliance.
  • An HT stamp inside the IPPC mark shows phytosanitary treatment.
  • KD-HT means the wood was both kiln dried and heat treated.

However dry the wood is, a pallet without the HT code in an IPPC mark is not ISPM 15 compliant.

Which one do you need?

Situation Specify
Domestic shipment, no moisture requirement Neither (green is fine)
Domestic shipment with a moisture limit, or sealed containers KD19
Export, no moisture requirement HT (ISPM 15)
Export in containers, or buyer with a moisture limit KD-HT
Canada to US (per Costco's policy) HT not required at the border
Mexico to US (per Costco's policy) HT required

Repaired or remanufactured pallets must be re-treated and re-marked for ISPM 15 even if the original lumber was HT.

Verifying each on delivery

  • Moisture: check with a moisture meter on arrival, or ask the supplier for kiln records. The Uniform Standard points to ASTM D4442 and D7438 for measuring wood moisture. Put the verification method in the RFQ if moisture matters to you.
  • Heat treatment: look for a legible, bordered IPPC mark on at least two opposite sides, with the country code, producer number and HT code. Ask for a certificate or letter of compliance if customs or your customer needs one.

How they appear on a spec

A PDS-style spec sheet lists them separately under treatments: "ISPM-15 Compliance: Heat Treatment (HT)" and "Conditioning: Kiln Dried, 19% EMC". An RFQ should do the same, and say where the ISPM marks go and whether a moisture certificate is needed.

How palletdesign.ai uses them

palletdesign.ai treats moisture and heat treatment as separate settings, as they should be:

  • Moisture: green or KD19. KD19 lowers the weight estimate and multiplies lumber cost by 1.15 in the engine's default cost assumptions.
  • Heat treatment: on or off. When a design is flagged for export, heat treatment is required, and the engine blocks the design until it is on. HT adds a default $1.50 per pallet to the indicative cost and "HT (ISPM-15)" to the classification line.

For a GMA-style 48 x 40 mixed hardwood pallet, the engine's indicative total is about $15.45 green and untreated, $16.87 kiln dried, and $1.50 more with HT. These are default assumptions for comparison, not quotes. See heat-treated pallets and pallet cost.

Questions

Is kiln dried the same as heat treated?
No. Kiln drying lowers moisture content; heat treatment is the ISPM 15 pest treatment (56 °C core for 30 minutes) with an IPPC mark. A pallet can be one, the other, or both (KD-HT).
Do export pallets need to be kiln dried?
Not for ISPM 15, which requires treatment such as HT, not a moisture level. Some buyers add a moisture limit, for example below 19% for containerized loads.
What does KD-HT mean on a pallet?
The lumber was kiln dried and heat treated. The HT part must appear in the IPPC mark for ISPM 15 compliance.

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