Wood Properties and Manufacturing Characteristics
top of page
top of page
Mechanical & Physical Properties
Physical and mechanical properties of western juniper have been examined and markets for a wide
variety of juniper products have been explored. Examples of products that have been explored include:
cement/woodfiber composites, particleboard, hardboard, animal bedding (shavings), fencing, decking,
interior doors, paneling, flooring, veneer, furniture, and novelty items.
Researchers at the USDA Forest Products Laboratory in Madison, WI, have characterized the fiber
properties and chemistry of western juniper and summarized the results in the report:
Basic Fiber and Chemical Properties of Western
Western juniper heartwood is highly durable (similar to redwood and cedars) and has aromatic properties
like its close relative eastern redcedar (Juniperus virginiana). The color of the wood varies from
milky white to deep reddish-brown and has large, swirling grain patterns and bands of heartwood mixed with
sapwood, similar to eastern redcedar. Tests have shown juniper wood to machine, glue, and finish well.
Once dried, juniper wood shrinks and swells less than many other Pacific Northwest species such as
Douglas-fir, ponderosa pine, and western redcedar. Juniper has some unique bending properties.
After being soaked in hot water, thin (1/32"-1/16") samples have been
tied into intricate knots without splitting.
Juniper wood is slightly more dense than ponderosa pine. The wood is also quite hard for a softwood:
about 35% harder than ponderosa pine, but only about ½ as hard as red oak. Juniper is about 70% as stiff
as ponderosa pine, and 85% as stiff as incense-cedar, meaning the wood deforms relatively easily under
loads. The table below compares some of the mechanical and physical properties of western juniper with
other commonly used woods.
Mechanical and Physical Properties of Western Juniper and Other Commonly Used
||Specific Gravity @12% MC
|Compression Strength-parallel to grain @12%
||MOE- Bending Stiffness @12% MC (Million psi)
||MOR-Bending Strength @12% MC (psi)
|northern red oak
||Hardness @12% MC (lbs.)
|| Volumetric Shrinkage (%)
||Nail Withdrawal Strength (side grain) (psi)
|northern red oak
Specific Gravity- Similar to density. Calculated as the weight of a sample of wood (oven dry) divided by
the weight of an equal volume of water. In this instance, the wood's volume was measured when the wood
was at 12% moisture content. Another way to look at specific gravity is- If a wood species has a
specific gravity of 0.44, then the wood is 44% as heavy as water.
Density- Density of the wood in lbs. per cubic foot at 12% moisture content.
Compression Strength- Answers the question, "How strong is the wood when used as a column, such
as a wall stud?". Determined by loading a wood sample as a column and recording the stress (psi) at the
proportional limit. The proportional limit is a point on a graph of deformation versus load. The
proportional limit is the point at which there is no longer a straight-line relationship between load (lbs.)
and the amount the wood column deforms in inches. A low compression strength indicates the wood may
crush fairly easily if used as a support column.
Bending Stiffness- Answers the question, "How stiff is the wood when bent like
a floor joist?". Determined by loading a wood sample as a beam and recording the stress (psi) at the
proportional limit. (see discussion of compression strength above for a description of proportional limit).
A low stiffness value indicates the wood may be "spongy" or "springy" if not adequately supported in
decking. Long, unsupported spans would be unwise for floor joists.
Bending Strength- Answers the question, "How strong is the wood when bent
like a floor joist?". Similar to bending stiffness, except the wood beam is loaded until it breaks. Note
the distinction between stiffness and strength. Stiffness is how easily the wood bends, strength is how
much force it takes to break the sample.
Hardness- Answers the question, "How resistant is the wood to wear and marring, such as when
used for flooring?". Hardness is measured by recording the amount of force it takes to embed a 0.444
inch diameter ball to half its diameter into the wood. A low hardness value means the wood would dent
easily if used in flooring.
Volumetric Shrinkage- Answers the question, "How stable is the wood?". Table values are percent
shrinkage from green to ovendry. This value is useful for comparisons to other species. As an example, a
ponderosa pine board will shrink, on the average, 9.7% in total volume from green to oven dry. Western
juniper will only shrink 82% as much as ponderosa pine. Actual inches of shrinkage in the radial and the
tangential direction may be calculated using published shrinkage coefficients. These values for western
juniper are 0.00111 in/in/% change in moisture for the radial direction and 0.00155 for the tangential direction
(see Burke 1994).
Nail Withdrawal Strength- Answers the question, "How well does the wood hold a nail?". Measured
as the amount of force required to pull a nail from the wood. A low nail withdrawal value would indicate
that nails may pop up easily if the wood shrinks or swells or that nailed joints may be excessively weak.
Table values for species other than western juniper are estimated using a formula from the USDA's Wood
The last 4 properties (machining, gluing, finishing, and bending) in the table are subjective. The
table lists those properties as: E (excellent), VG (very good), G (good), F (fair), or P (poor).
Machining- How well does the wood machine? Does the wood tend to burn or chip during cutting,
surfacing, and moulding operations?
Gluing- Does the wood glue well? Do chemical extractives in the wood prevent the formation of
Finishing- How easy is it to keep a finish on the surface?
Bending- How well does the wood bend? Does
the wood split during bending?
Values for western juniper from Dr.
Ed Burke, School of Forestry, University of Montana. Other values are from
the Wood Handbook: Wood as an Engineering Material, USDA Forest Service, Forest
Products Laboratory, Ag. Handbook #72, 1987.
top of page