Everything you need to know about timber products
Why should I care about timber products?
We’ve helped a lot of folks sell their timber over the years, and one of the questions we get asked time and time again is, “How do timber buyers and mills decide what sort of products my timber will be turned into? Does the logger classify the cut as he loads, or does the mill make that determination and document it on the receipt?”
This is an excellent question, and it’s important for prospective timber sellers to understand the answer since it can go a long ways in ensuring you’re getting a fair deal from your timber sale.
The answer is not as complicated as you might think, but there are some ins and outs that are important to understand first.
To make things easier, we’ve put together this comprehensive guide to help explain the different types of timber products, how those products are classified, how they’re milled, and finally, we tie it all together by explaining how timber buyers and mills decide exactly how to classify a cut of timber.
Back to basics: What is timber used for?
First, it’s important to understand that timber products are primarily classified based on how they will be used, and how well suited they are for that use. When classifying sawtimber products (timber cut from a single log), there are a few definitions that are useful to know:
- Dimension lumber refers to lumber that will be used as supports for buildings and structures, such as 2x4s and 2x6s, and is classified based on the overall strength and rigidity of the lumber. Dimension lumber that can handle heavier loads will receive a higher grade, while lumber that’s weaker or less rigid will receive a lower grade.
- Boards is a general term that refers to lumber that is cut for decorative use. In this category, products are classified based on appearance rather than overall strength, with higher grade boards ideally having very few knots, holes or discolorations.
- Poles refers to lumber that will be used to support vertical loads (e.g. utility poles for holding up electrical wires). Wood products that fall into this category are graded based on overall height and diameter, straightness, and strength.
What about trees that don’t make the cut for sawtimber?
It’s in the interest of the mill to get as much use and value out of each tree as possible. But what happens when a tree isn’t thick enough or tall enough to be used for dimension lumber? Or if the tree is cut into lumber, what happens to the leftover bits that couldn’t be cut into boards?
In these cases, smaller trees and leftover pieces can be turned into products that don’t rely on factors like strength, rigidity, or appearance, such as pulpwood or wood chips.
- Pulpwood refers to trees or logs that are used to manufacture paper products such as cardboard and fiberboard, as well as absorbent pulp
- Wood chips are made from trees or logs that have been run through a wood chipper, and are used as raw material for producing wood pulp, or as mulch in landscaping and gardening, fuel for energy plants, surfacing for playgrounds and parks, and loads of other applications (see more here https://en.wikipedia.org/wiki/Woodchips)
Now that we’ve got a basic understanding of timber products, let’s take a closer look at how each product is classified, how it’s milled, and how it’s measured and valued by the mill. First, let’s go over a few forestry terms that will be useful to know:
- DBH or Diameter Breast Height: Diameter Breast Height, or DBH, is a standard for expressing the diameter of the trunk of a standing tree. In the US, DBH is measured at a height of 4.6 feet (1.4 meters). A lot of timber product classifications will specify their requirements in DBH, so this is a good one to know.
- Cord: For some timber products, the overall value may be expressed in either tons or in cords. So how much wood is in a cord? Assuming that the wood has been lined up in the same direction, is parallel, and is as close together and compact as possible, a cord refers to a volume of wood that is 4 feet high, 4 feet wide, and 8 feet long (128 cubic feet total). The weight of a cord of wood can vary depending on the density of the product it’s measuring, and can range between 2,500 lbs. for softwood and up to 5,000 lbs. for hardwood.
- Hardwood: Hardwood refers to trees with broad, flat or scalloped leaves that keep their seeds in an outer casing, such as a nut or berry. Most hardwoods are deciduous, meaning they drop their leaves each year. There are exceptions however — holly and magnolia, for instance, are evergreen hardwoods. You may also hear these referred to as angiosperm (literally meaning “vessel seed”) trees.
- Softwood: Unlike hardwood trees, softwood trees reproduce by forming cones which emit pollen, which then spreads to other trees by the wind (if you live in Georgia, you’re most likely familiar with the “yellow pine pollen” that fills the air every Spring). Likewise, these trees tend to be evergreen, rather than dropping their leaves in cycles each year. Most softwood is produced by conifer trees — spruces, firs, and pines. You may also hear these referred to as gymnosperm (literally meaning “naked seed”) trees.
Classifying Timber Products
It’s time to talk about how some of the most common timber products are measured, classified, and valued. We’ll also talk a little bit about the harvesting process, and what goes into milling the final products.
Pine trees that have a certain taper, straightness and overall diameter are harvested and processed to become poles. In the South, these are typically harvested from carefully maintained stands of Southern yellow pine trees, which includes species such as longleaf, slash, loblolly, and shortleaf (https://en.wikipedia.org/wiki/Yellow_pine). These trees are ready for harvest at around 30 years of age or older, although they can sometimes be ready as early as 25 years, or 22 years for poles that will be used as marine pilings.
When picking trees to be used as poles, a logger will look for the following general criteria:
- 10-20” DBH
- 30’ height, or more
- Straight healthy trunk with few limbs
The first two criteria are pretty concrete, but what about the third one? How do you decide what makes a trunk straight and healthy?
There are lots of factors, but here are some of the main ones a logger or forester will consider:
- Less than 1” sweep for every 10 feet of stem
- Less than 4 knots per linear foot, and less than 6” diameter of knots per linear foot
- No branches in first 10 feet
- No sharp angled branches or a fork at less than 32 feet
- No stem cankers for at least 32 feet
Once the trees are selected, how do they get turned into poles?
It goes like this:
- Cut: The selected trees are cut down at the base and sent to the mill.
- Clean: At the mill, the trees are run through a debarking machine which removes the outer layer of bark and the cambium (the layer of tissue underneath the bark), and an inch is cut from the bottom of each pole to make sure the base is square
- Classify: The poles are assessed for quality, and the length and class are marked on the bottom
- Treat: A kiln is used to dry the poles for about 3 days at 200 degrees Fahrenheit, then chemically pressure treated to prevent rot
- Grind: Finally, the bark and shavings from the poles are run through a grinding mill and turned into fibers, which in turn can be used to power the kiln and boilers at the mill
Since trees that will be used for pine poles have to meet more rigorous physical standards than other timber products, the overall per ton stumpage value for poles tends to be the highest of any product. How much higher? Historically, pine poles can fetch as much as 2-3x the value of sawtimber, and 8-10x the value of pulpwood.
If you’re selling your trees, that can have a big impact on your bottom line.
Sometimes called “peeler logs,” a ply log is a log or tree that’s used to produce sheets of veneer, which in turn are stacked and treated to produce plywood. The exact specifications for ply logs will vary depending on the mill, but in general, the log or tree must be:
- Relatively free of knots or blemishes
- Of sound wood
Some mills will also have a length requirement, usually along the lines of “accepts logs in multiples of 8’9″ up to 35′,” which has to do with the fact that during the milling process, the ply logs will be cut into segments of ~8’ before being turned on a lathe to produce the sheets of veneer.
Diameter requirements can also vary, but in general it’s good to know that the larger the diameter of the tree, the higher the value for the log.
So how does the milling process for ply logs work, and how does a tree get turned into a sheet of plywood?
It goes like this:
- Cut: Trees are selected based on the mill’s specifications and requirements, then cut down at the base
- Clean: Trees are taken to the mill and run through a debarking machine to remove the outer layer of bark and the cambium
- Section: Logs are run through a saw that cuts them into 8’ sections (i.e. a 32’ long log would produce four 8’ sections)
- Peel: Each log is turned against a sharp knife or lathe, which peels the log into a long ribbon of wood
- Treat: The ribbons of wood are cut into individual sheets of veneer and chemically treated to prevent rot
- Bind: The sheets of veneer are run through a glue spreader, stacked to the necessary thickness for the final plywood product, then run through a hot press to bind them together
- Finishing: The finished sheets are trimmed to size, patched if needed, sanded, and finally, inspected for quality.
Plywood can be produced from either hardwood or softwood, and both types have advantages and disadvantages.
Hardwood plywood typically has excellent strength and stiffness, making it ideal for demanding uses such as heavy-duty floor and wall structures.
Softwood plywood is used for construction and industrial purposes as well, although usually in less demanding situations than hardwood plywood. It’s also used to make furniture due to what many consider its “rustic” or “antique” look, and in making boats because of its high strength to weight ratio.
Although it varies depending on local timber markets, ply logs often fetch a value that is equal to or slightly higher than sawtimber.
Sawtimber, or sawlogs, refers to logs or trees that are large enough, and of a high enough quality, to be sawn into lumber. Just like with ply logs, when classifying trees for sawtimber, a logger or forester will look for:
- Straightness of the trunk
- Quality and soundness of the wood (few knots or blemishes)
In addition, they will look for trees that are 14” DBH or more (higher diameters will fetch a higher value).
Once the trees are selected and cut down, they are taken to the mill and sawn into lumber. The waste products are converted into chips for fuel, or pulp for paper production. Sawtimber products can be cut from both softwood and hardwood trees.
So how does a mill turn a round log into square boards, while minimizing waste? The most common technique is what’s known as “plainsawn,” also sometimes called “flatsawn” or “through-and-through.” Plainsawn boards are cut in parallel through the pith of the log, one after the other. The cut is fast, efficient, and yields minimal waste, hence it’s popularity.
You may also hear of boards being “quartersawn,” “true quartersawn,” or “riftsawn.” These terms refer to boards that have been cut radial to the grain of the log. The difference between the three is the resulting angle of the grain, with quartersawn being closer to 90 degrees, and riftsawn being closer to 30-60 degrees.
Want to learn more about the different types of sawtimber cuts (including fantastic pictures, diagrams, and videos)? We highly recommend this article by Christie Nicholson at Core77 http://www.core77.com/posts/24890/how-logs-are-turned-into-boards-part-1-plainsawn-24890
Although overall value for sawtimber depends heavily on the tree quality, sawtimber products are usually valued higher than Chip-n-Saw, and lower than pine poles.
Trees or logs that are too small to be turned into poles or sawtimber are instead processed by a method called Chip-n-Saw, or CNS. Trees used for this method will typically be medium-sized (10-13” DBH), and are often harvested during an early thinning of a larger timber stand.
The milling process for CNS is very similar to the other products, although the end result is slightly different. Logs are sent to the sawmill where the outer layer is ground away. Larger logs are slabbed and sawn to create 2x4s and other small dimension lumber. Smaller logs in the load are chipped for fuel or paper pulp.
Although CNS products don’t fetch as high a value as poles, ply, or sawtimber, they tend to be valued higher than pulpwood.
Trees that aren’t big enough or of a high enough quality to be used for CNS can be turned into pulpwood, which is used to manufacture paper, absorbent pulp, cardboard, fiberboard, and other fiber-based products. Pulpwood can be produced from either hardwood or softwood.
Trees that are designated for pulpwood are typically 6-9” DBH, and harvested during an early thinning of a timber stand, much like CNS.
So how do wood chips get turned into pulp, and how does that pulp get turned into paper? There are a couple different ways.
With mechanical pulping, machines are used to grind wood chips into pulp, creating a pulp that retains most of its lignin (a natural glue that binds plant cellulose fibers). Due to the short fibers created by this process, the resulting paper is most suitable for newspapers, phone books, and other low-strength paper uses.
With chemical pulping, chemicals separate the lignin from the cellulose, resulting in a pulp that can be used to make stronger paper products.
Due to the low requirements to produce it, pulpwood tends to fetch the lowest value of all timber products.
Putting It All Together
As the size of the trees in a timber stand increase in height and diameter, they become more valuable since more product classes are available. When a tree grows into a more valuable product class, this is called “ingrowth.”
In a properly managed timber stand, trees with the highest potential will be left to grow into high value products, such as poles and sawtimber — a process that can take 25 to 30 years or more. To help the higher-quality trees reach their full potential and value, lower quality trees will be selected and removed from the stand, often around the 12 – 15 year mark, depending on your stand’s genetics. This is what’s known as a “thinning.”
Once harvested, the lower quality trees are processed into CNS or pulpwood, which return lower but still substantial values.
So who classifies the timber?
Does the logger classify the cut as he loads, or does the mill make that determination?
The answer is both.
The timber buyer (the person who bought the timber from the landowner) has weekly quotas with mills for certain products. As the logger (loggers are either contractors or employees of the timber buyer) is cutting down the timber, they stack the wood in piles based on their product and then load them on a trailer to deliver to the mill.
It’s not always straightforward though. Sometimes, the person loading the wood on the trailers will try to slip in lower quality wood in hopes that it will still pass inspection at the mill, but sometimes the mill rejects the whole load and classifies it as a lower grade product. This means there’s some amount of risk and uncertainty involved.
Once the mill classifies the product and weighs it, they print a scale ticket for documentation.
Although we’ve included a lot of information, this is still just a basic introduction to the different timber products that can be produced from a stand of trees. If you’re seriously considering selling your timber, we highly recommend talking to a professional forester before doing so or reach out to us at Timber Update.
In our experience, landowners who consult with a professional forester before selling their timber can see as much as a 20-30% higher value on their final sale compared to a landowner who goes the DIY route.
Getting in touch with a pro is easier than you think, just click the button below to get started today: