quarter sawn lumber

Why Does Dried Wood Absorb Moisture?

Wood and Moisture: It’s All Biology

The hardwood lumber that you buy at the lumberyard began as a living tree. As a living tree, the trunk of the tree provided a way to transport water from the roots to the leaves. When the tree is cut down that water moving system is still present in that tree and much of that water is still in the lumber when it is first sawn.

Hardwood lumber just cut, referred to as green lumber, can have a moisture content of 40% or more! After hardwood lumber is sawn, it is typically air-dried to around 15% moisture content. Hardwood lumber will be continued to be dried in a kiln to a moisture content of 6-9%.

Wood is hygroscopic, which means just like a sponge the moisture content will change depending on the relative humidity of the surrounding air. When humidity increases, the wood absorbs moisture from the air causing the wood to expand. When the humidity decreases, the wood releases water into the air and the wood shrinks.

What Direction Does Wood Expand In?

When wood expands and contracts because of changes in moisture content, hardwood will move in a predictable way. Wood shrinks most in the direction of the annual growth rings (tangentially), and half as much across the rings (radially), and only slightly along the grain (longitudinally). or from the center of the tree to the outer edge).

Hardwood shrinks most in the direction of the annual growth rings (tangentially), about half as much across the growth rings (radially), and only slightly along the grain (longitudinally).

Flat-sawn boards will cup away from the heart of the tree. The shrinking will occur mostly in its width.
Rift-sawn boards will warp and shrink into a diamond or trapezoidal shape.
Quarter-sawn boards will shrink slightly in both length and width.

What Do I Do About Moisture and Wood Movement?

The solution to this problem is quite simple: don’t stop the wood from moving, but rather account for its movement. With a little bit of knowledge, you can predict the degree of wood movement, and take action to accommodate the movement.

Differences to Know When Designing With Quarter Sawn Hardwood

Quarter sawn hardwoods are beautiful and distinctive. The unique look of quarter sawn hardwoods lend itself to an array of design styles, from traditional to modern.

But, when designing with solid quarter sawn hardwoods, it is important to understand how the uniqueness of this wood comes with a limitation in product width.

Why Is Quarter Sawn Lumber Narrow?

In order to obtain the distinctive straight-grained appearance of quarter sawn lumber, logs must be sawn in a different way. The log is first cut in half and then into halves again. After being cut into quarters, each quarter section is placed on the mill in a position so that the annual rings are as close to 90 degrees (perpendicular) to the face of each board as possible when sawn.

By sawing the log in this way, quarter sawn lumber yields more waste and therefore the end result is narrower boards, in comparison to plain sawn lumber sawing methods.

Print       plain-sawn

 

Why is Quarter Sawn Hardwood More Expensive?

Quarter sawn hardwood can command a premium over plain sawn lumber. This is primarily due to a more limited availability of quarter sawn lumber – both because of the lower number of boards made from each log and combined with a much smaller number of suppliers producing this kind of lumber. This limited availability of quarter sawn lumber results in a premium price for this type of lumber.

Is Quarter Sawn Hardwood Worth It?

The principal benefit of the quarter-sawing technique is that all of the grain will be straight, resulting in a more dimensionally stable product. Quarter sawn lumber typically does not warp, twist, or cup. A narrow grain pattern is typically evident on the face of the board. Flecks are generally evident in quarter sawn red oak and white oak, but can also be seen in other species. Read more about quarter sawn wood.

Is Quarter Sawn Wood Still A Green Choice?

Many have asked whether the higher waste involved in making quarter sawn wood result in a product that is less environmentally friendly than traditional lumber. The answer is simple – quarter sawn wood is a sound environmental choice. (Read more on why solid wood is a great design choice for our environment.) Companies who produce quarter sawn lumber use the rest of the log in a variety of ways. Bark can be turned into mulch and wood chips supply paper companies, while sawdust is often used on-site to fuel drying kilns. No part of the log is left unused.

What is the difference between Quarter Sawn, Rift Sawn and Plain Sawn Lumber?

When lumber is cut from logs, it is typically cut in one of three ways: quarter sawn, rift sawn or plain sawn. Each type of lumber is dependent on how the log is oriented and cut at the sawmill. The result is a particular orientation of the growth rings on the end grain of the board and is what defines the type of lumber.  The type of cut also determines the figure in a piece of wood and the wood’s mechanical properties.

Sound too confusing? This graphic will help…

PLAIN SAWN / FLAT SAWN
Most common, least expensive
Plain sawn, also commonly called flat sawn, is the most common lumber you will find. This is the most inexpensive way to manufacture logs into lumber. Plain sawn lumber is the most common type of cut. The annular rings are generally 30 degrees or less to the face of the board; this is often referred to as tangential grain. The resulting wood displays a cathedral pattern on the face of the board.  See pictures here.

QUARTER SAWN
More expensive than plain sawn material
Quarter sawn wood has an amazing straight grain pattern that lends itself to design. Quarter sawn lumber is defined as wood where the annular growth rings intersect the face of the board at a 60 to 90 degree angle. When cutting this lumber at the sawmill, each log is sawed at a radial angle into four quarters, hence the name. Dramatic flecking is also present in red oak and white oak.  Find out more.

QuartersawnRiftsawnLumberDifference_Diagram3

Comparison of typical cutting methods for each type of lumber

RIFT SAWN
Most expensive, least common
Rift sawn wood can be manufactured either as a compliment to quarter sawn lumber or logs can be cut specifically as rift sawn. In rift sawn lumber the annual rings are typically between 30-60 degrees, with 45 degrees being optimum. Manufactured by milling perpendicular to the log’s growth rings producing a linear grain pattern with no flecking. This method produces the most waste, increasing the cost of this lumber. Rift sawn lumber is very dimensionally stable and has a unique linear appearance.  Refer to additional pictures.

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