Hardwood Floors Oct/Nov 2019

SPECIES SPECS E l m RESOURCES

Ulmus genus

GRAIN: The grain is normally straight, but is sometimes interlocked. Its texture is described as coarse, and rather woolly. Figured grain patterns are common, and normally a desired feature with elm. Elm is sometimes confused with ash due to the similarities in color and grain pattern, although elm commonly has wavy, zigzag patterns in the latewood that can be visible even on plainsawn faces. The heartwood ranges from a light orange-brown to gray or olive, sometimes with darker streaks. The sapwood normally is white, to greyish white, to light brown and is well-defined. The grain is ring-porous.

The elm (Ulmus genus) contains about 60 species, which, like maple, can be divided into two general groups: hard elms, and soft elms. For the purpose of the wood flooring industry, we will focus on some of the more-common elm species such as the hard elm species rock elm (Ulmus thomasii); and the soft elm species American elm (Ulmus americana), English elm (Ulmus procera), and red/slippery elm (Ulmus rubra).

HARDNESS (JANKA):

• Rock elm: 1320 • American elm: 830 • English elm: 810 • Red/slippery elm: 860

ORIGIN: Deciduous tree found primarily in North America, South America, Central America, Europe, Asia, and the Mediterranean. Six species of elm grow in the United States including the American elm, red/slippery elm, rock/hickory elm, winged elm, cedar elm, and the September elm.

DIMENSIONAL STABILITY: AVERAGE • Rock elm has a dimensional stability factor of 4.8 percent (radial) and 8.1 percent (tangential), meaning this species may shrink/swell up to 8.1 percent of its given width, depending on how it’s cut, when going from green (30 percent MC) to oven-dried (0 percent MC). • American elm has a dimensional stability factor of 4.2 percent (radial) and 9.5 percent (tangential). • English elm has a dimensional stability factor of 5.0 percent (radial) and 7.0 percent (tangential). • Red/slippery elm has a dimensional stability factor of 4.9 percent (radial) and 8.9 percent (tangential). DIMENSIONAL CHANGE COEFFICIENT: • Rock elm = .00165 (radial), .00285 (tangential) • American elm = .00144 (radial), .00338 (tangential) • English elm = unknown • Red/slippery elm = .00169 (radial), .00315 (tangential)

Readily available, but threatened by two diseases: Dutch elm disease, which is a disease first introduced in the 1930s caused by the elm bark beetle, and phloem necrosis disease, both of which have killed millions of elm trees throughout the world. There are efforts underway to restore the American elm.

USES: Elm is commonly used in cabinetmaking, chairs, turnery, veneers, hockey sticks, archery bows, boat and ship building, boxes and crates, baskets, pallets, gymnasium equipment, coffins, and in flooring.

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