Betulaceae Genus
ORIGIN:
The Betulaceae genus (birch) family contains nearly 60 species of trees and shrubs. For the wood flooring industry, we will only focus on yellow birch (Betula alleghaniensis), sweet/red birch (Betula lenta), and silver/European birch (Betula pendula). Some other woods that are within the birch family include alder (Alnus Mill.), hornbeam (Carpinus L.), and hazelnut (Corylus L.)
Yellow and sweet/red birch grow primarily in eastern Canada, in the northeastern United States and Lake states, and along the Appalachian Mountains. Silver/European birch grows throughout Europe, including the UK and Scandinavia. Note: The birch tree is the state tree of New Hampshire, and the National tree of Russia, Finland, and Sweden.
USES:
Birch is commonly used in residential flooring, gym flooring, furniture, cabinetry, millwork, turnery, violin bows, for decorative veneers, and as plywood. Birch is also used for pulp to make paper, distillation products, syrup, toothpicks, and ice cream sticks. Russian birch is commonly used to make high-quality plywood often used as a platform/backing for engineered flooring. Native Americans used birch bark from fallen trees to make canoes.
COLOR:
In yellow birch, sapwood is creamy yellow or pale white; heartwood is light reddish brown tinged with red. In sweet/red birch, sapwood is light colored, and the heartwood is dark brown tinged with red. In silver/European birch, wood may be creamy-white to pale brown and can be somewhat featureless with no color distinction between sapwood and heartwood.
GRAIN:
Birch has a fine, close-grained texture that is generally straight. Birch normally has distinct, inconspicuous growth rings. The grain can also be figured or wavy. Figured birch is usually more expensive and sought after for decorative purposes.
HARDNESS (JANKA):
- Yellow birch averages 1260.
- Sweet/red birch averages 1470.
- Silver/European birch averages 1210.
DIMENSIONAL STABILITY: AVERAGE
- Yellow birch has a dimensional stability factor of 7.3 percent (radial) and 9.5 percent (tangential), meaning this species may shrink/swell up to 9.5 percent of its given width, depending on how it’s cut, when going from green (30 percent MC) to oven-dried.
- Sweet/red birch has a dimensional stability factor of 6.5 percent (radial) and 9.0 percent (tangential), meaning this species may shrink/swell up to 9.0 percent of its given width, depending on how it’s cut when going from green (30 percent MC) to oven-dried.
- Silver/European birch has a dimensional stability factor of 6.3 percent (radial) and 8.6 percent (tangential), meaning this species may shrink/swell up to 8.6 percent of its given width, depending on how it’s cut when going from green (30 percent MC) to oven-dried.
DIMENSIONAL CHANGE COEFFICIENT:
- Yellow birch = .00256 (radial), .00338 (tangential)
- Sweet/red birch = .00256 (radial), .00338 (tangential)
- Silver/European birch = No Data
SPECIFIC GRAVITY:
- Yellow birch = .62
- Sweet/red birch = .65
- Silver/European birch = .66
NAILING:
There are no known issues with nailing birch.
SANDING:
Extra care should be taken during sanding and finishing, as sanding marks may become more apparent due to the tight grain, density, and light color of the species. It is often required to bring the sanding sequence to a higher grit to minimize visible scratches in birch. Birch can be difficult to stain and may appear blotchy.
Sources: The Wood Database; Copyright © 2008-2016, Eric Meier | Wood Handbook (Wood as an Engineering Material), USDA Forest Products Laboratory | A Guide to the Useful Woods of the World; Copyright © 2001, James H. Flynn, Jr. and Charles D. Holder | Missouri Dept. of Conservation | Bigstock