Relationship of Fir shrinkage to drying temperature - Ask Extension
I recall an article which indicated drying green lumber at lower temperatures reduced the ultimate shrinkage of the wood vs drying faster at higher te...
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Relationship of Fir shrinkage to drying temperature #922945
Asked December 18, 2025, 12:29 AM EST
I recall an article which indicated drying green lumber at lower temperatures reduced the ultimate shrinkage of the wood vs drying faster at higher temperatures.
Do you have such an article or research paper?
Lane County Oregon
Expert Response
Greetings,
Were either of these the articles you saw?
Air‑ and Shed‑Drying Lumber (EM 8612) – OSU Extension publication by James E. Reeb and Terrence D. Brown. https://extension.oregonstate.edu/sites/extd8/files/catalog/auto/EM8612.pdf Wood and Moisture Relationships (OSU Extension) – Companion resource referenced in EM 8612. https://extension.oregonstate.edu/catalog/em-8600-wood-moisture-relationships
Were either of these the articles you saw?
- Explains how controlling the drying rate through air drying or shed drying helps minimize shrinkage and degrade.
- Notes that drying lumber to the average moisture content where it will be used ensures minimal dimensional change (shrink or swell).
- Discusses how drying below the fiber saturation point (25–30% MC) increases strength but also introduces shrinkage, which is more manageable at lower drying temperatures.
Thank you for your time. These articles do not address my question. Let me try again.
Are there any studies which document the impact on softwood lumber shrinkage by lowering the kiln drying temperature and increasing the drying time?
Thank you for your time. These articles do not address my question. Let me try again.
Are there any studies which document the impact on softwood lumber shrinkage by lowering the kiln drying temperature and increasing the drying time?
Hi Brent,
I think the article you're referring to was written by a former coworker of mine at Oregon State University - Milota, M.R. (2000). Warp and shrinkage of hem-fir stud lumber dried at conventional and high temperatures. Forest Products Journal 50(11):79-84 I can't find the full text of the article online, so I just contacted the author (Mike Milota) to get a copy. Here's the abstract:
"In this study, 2 by 4 hem-fir stud lumber was dried at conventional (180 °F, 82 °C) and high temperatures (240° to 270 °F, 116° to 132 °C). Drying wood at a high temperature reduced the average amounts of bow and crook measured against a straight-edge, but not significantly. However, the number of pieces exceeding the limits allowed by the grading rules appeared to be more a function of final moisture content than drying temperature, suggesting that boards predisposed to warp will do so regardless of temperature. Increased thickness shrinkage for the wood dried at high temperatures might necessitate an increase of 0.005 to 0.010 inch in the green target thickness if a similar level of skip at the planer is to be maintained. The value of the product was not significantly different for wood dried at conventional and high temperatures, but high temperatures reduced the drying time by 50 percent."
I think the article you're referring to was written by a former coworker of mine at Oregon State University - Milota, M.R. (2000). Warp and shrinkage of hem-fir stud lumber dried at conventional and high temperatures. Forest Products Journal 50(11):79-84 I can't find the full text of the article online, so I just contacted the author (Mike Milota) to get a copy. Here's the abstract:
"In this study, 2 by 4 hem-fir stud lumber was dried at conventional (180 °F, 82 °C) and high temperatures (240° to 270 °F, 116° to 132 °C). Drying wood at a high temperature reduced the average amounts of bow and crook measured against a straight-edge, but not significantly. However, the number of pieces exceeding the limits allowed by the grading rules appeared to be more a function of final moisture content than drying temperature, suggesting that boards predisposed to warp will do so regardless of temperature. Increased thickness shrinkage for the wood dried at high temperatures might necessitate an increase of 0.005 to 0.010 inch in the green target thickness if a similar level of skip at the planer is to be maintained. The value of the product was not significantly different for wood dried at conventional and high temperatures, but high temperatures reduced the drying time by 50 percent."
Thank you very much. Bren.
