Frequently Asked Questions (FAQs)
General
The Forest Products Laboratory was established in 1910. Learn more about the Forest Products Laboratory.
As of 2023, about 80 scientists work at the Lab. The total number of staff is about 168. Learn more about the Forest Products Laboratory or view our staff directory.
We offer in-person tours on the third Thursday of each month beginning at 9:30 a.m. and lasting approximately one hour. Visit our events page for more details, and email SM.FS.mailroomFPL@usda.gov to reserve your spot.
We also have a virtual tour, available through the National Forest Explorer app on your smartphone (get it at Apple App Store or Google Play). You can also access the virtual tour in your web browser.
Wood Resources and Research
Treesearch is a public database of over 60,000 published research papers from the Forest Service, including those from the Forest Products Laboratory. You can view publications authored by Forest Products Laboratory scientists, or all Forest Service papers.
You can download the entire Wood Handbook for free: Wood handbook: Wood as an engineering material.
We do not identify wood species by photograph. Through our Wood Identification Public Service, you can send in samples of wood for the Forest Products Laboratory to identify.
As stated on the Wood Identification Public Service webpage, "in most cases, specimens are identified within four weeks of receipt."
Durable Solutions for Balconies and Decks is an illustrated guide that shows design principles and construction practices that improve the moisture performance of wood-framed balconies and decks in low-and mid-rise multifamily buildings. These practices will lead to longer life for the products used and to safer balconies and decks for residents.
The Forest Products Laboratory does not perform tests for private individuals or companies.
Wood Treatment
A living tree is about 50% water. When a tree is cut for lumber, boards are cut from the green wood then dried until the equilibrium moisture content (EMC) is reached. Depending on the specific gravity of a species, board size, and climate, covered boards outside can take a year or more to reach EMC. Kilns were developed to speed up this process. In short, the higher the temperature, the faster moisture leaves the center of a board, and the drier the air, the faster the surface of a board dries.
For more information, see the Wood Handbook, Chapter 4: Moisture Relations and Physical Properties of Wood.
Kiln dried and treated wood will be stamped "KDAT" (kiln dried after treatment). When purchasing products from a lumber yard, ask whether they have been treated.
Wood shrinks as it dries because water leaves the cells. In general, shrinkage in the longitudinal direction, which usually corresponds to the length of a wooden piece, is lower (0.1% to 0.2% from green to oven-dry). Radial shrinkage, which is perpendicular to the direction of the growth rings, ranges from 2% to 6%. Tangential shrinkage, which is in the direction of the growth rings, ranges from 7% to 12%. The values for individual species are available in the Wood Handbook, Chapter 4: Moisture relations and physical properties of wood (pages 4-8). For more information on drying methods and moisture content control, see the Wood Handbook, Chapter 13: Drying and control of moisture content and dimensional changes.
When selecting a finish, you should consider appearance, protection, cleanability, how properties of wood affect finish application, and how long it will likely last. Understanding how wood properties, finish, and environmental conditions interact makes possible to predict and avoid issues with finishing performance for most wood products. For detailed information on wood finish options, see the Wood Handbook, Chapter 16: Finishing wood.
Preventing sap from oozing out of lumber products requires setting the pitch so that it no longer flows as a liquid. When wood is heated enough, volatile compounds like terpenes leave the sap (resin), leaving only a stable rosin, the same as is used on violin bows. The pitch is set at the highest temperature during the drying process; this means that if wood becomes hotter in service than during this process, pitch can liquify again. Generally, wood is brought up to 160 °F in a kiln to set the pitch.