Does Kiln Dried (KD) lumber automatically mean it is Heat Treated (HT)?

That’s a great question and one that is often misunderstood.  The short answer is “No”, kiln dried lumber does not necessarily meet the requirements for heat treating.  Or put another way, not all kiln dried (KD) lumber is heat treated (HT) and not all heat treated lumber is kiln dried.

The term “kiln dried”, or KD, refers to lumber that has been dried in a kiln to a moisture content that does not exceed a specified maximum level. The key word here is “dried” and note there is no mention of temperature.  The term “heat treated”, or HT, refers to lumber that has been heated to a specific core temperature (56 degrees C) for a minimum of 30 minutes – note there is no mention of drying or moisture content.  

So…you can have KD lumber that has been properly dried using a low temperature drying schedule that does not meet the temperature requirements for heat treating.  Likewise, you can heat lumber so that it meets the HT requirements without drying it at all. In fact, it is not uncommon to produce HT lumber that is unseasoned (green).

If you are buying KD lumber, or any dry lumber for that matter, and it needs to be heat treated, make sure you specify HT when you place your order. That way the producer can label it properly with an HT mark or issue an HT certificate.  It may not be possible to certify material as HT after it has been shipped.  Similarly, if your HT lumber needs to be dry, you’ll need to specify that as well.

For more information, select “Heat Treatment (HT)” from the drop down menu under the “Services” tab on our website.