The Process of Obtaining Lumber for Construction From Trees

Posted October 10, 2018 | Tags: lumber in construction

Wood is one of the most common building materials. But you probably don’t think much about how it’s produced when they go to a nearby store and purchase a bit of lumber (sawn wood).

The truth is that few of us know anything about how wood is manufactured and what, precisely determines how it ends up looking, what dimensions, and various other factors that go into its performance.

The wood we use to build our houses and other architectural objects comes from over 2000 different species of trees scattered around the world.  Each of these species has a different level of humidity and density. Uniqueness doesn’t end there; the specific way in which the trunk of a tree is cut is the chief determiner in how each wood section will function and what characteristics it will have.

Let’s look at the most common of these cuts. But first, label the various parts of a trunk, moving from the outside in:

•    The Bark – This is the outer layer of the trunk. It is irregular and composed primarily of dead cells. It acts as a protective layer to the inner layers of the tree.

•    The Cambium – This is the layer that lies just beneath the bark. It is where the new cells that increase the diameter of the trunk year by year are generated.

•    The Sapwood – This is the younger wood in the tree. It is continually growing and is clearer than the outer layers with a higher amount of water and a smaller amount of the hardening component lignin.

•    The Heartwood – This is adult wood. It is darker than the sapwood and contains higher levels of lignin. This also makes it more rigid than the sapwood.

•    The Pith – This is the very center of the trunk. It the most rigid and cohesive part of the trunk and contains very little moisture.

It’s important to know these parts because they are an essential aspect of the classification of wood into hardwood and softwood. One of the factors used when making this classification is the proportion of heartwood to softwood inside the trunk that went into making the wood. Softwoods are less resilient but grow faster and are cheaper than hardwoods which are more resilient but slow growers and are more expensive.

Other things that determine the look of wood are the growth and medullary rings. The growth rings define the age of the tree while the medullary rings move the sap vertically along the tree.

The different ways to saw a Trunk

Rift Sawn Wood

The cut is perpendicular to the growth rings and keeps the grain of the wood visible. There are no fissures or deformation in the wood. More material is wasted in the process, however.

Quarter Sawn Wood

Here the cuts are made parallel to the axis of the trunk, of which there are four. The pieces obtained using this method have a high number of rings visible and are not very easily warped.

Live/Flat Sawn Wood

The wood is sawn horizontally along the chords of a circle that coincides with the trunk of the tree. This is the most commonly sawn wood. It isn’t the best quality, however, as there is a significant amount of heartwood and sapwood involved. The outer pieces are prone to warping while the centerpiece that contains the core will easily break.

Parallel Wood Boards

This method is similar to the flat sawing method. The significant difference is that in this case a smaller section is taken, reducing warping vulnerability.

Cantibay Sawn Wood

The wood is sawn along a triangle inscribed inside the circle of the trunk. It allows wide boards to be obtained from the trunk while helping avoid the brittle core of the trunk. It also reduces waste.

Quarter Sawn Wood

In this system, the trunk is divided into four quarters. The pieces are then sawn that have the best appearance and strength from each quarter.

Whole Piece Wood

The bark of the trunk is eliminated, and a single square block of wood is obtained, allowing the wood to be used to its maximum potential.

Cross Cut Wood

The heartwood is utilized to its maximum potential. Smaller pieces are obtained from the surrounding sapwood.

Interlocked Cut Wood

The boards that intersect with the core of the trunk are the first to be cut. The remaining wood boards may be thinner, but they are much more resistant to deformation.

Deformation Cut Wood

This is used on wood which has a high moisture content. Different shapes are cut out of the wood depending on the way the growth rings are arranged. 

Ultimately, how we cut wood is almost as diverse as how we use it. This versatile building material has been part of our architectural history and heritage as humans and will continue to be so for the foreseeable future.

I hope knowing a little more about how a tree becomes lumber will make your trip to The Home Depot or Lowe’s lumber yards a bit more interesting.
 


 

 

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