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  • Lumber Terms Used On This Site And Their Meaning

  • Board Foot

    A unit of quantity measurement for rough lumber. A board foot of lumber measures 12" square x 1" thick. To compute board footage take the length of the material in feet x width of material in inches and divide that product by 12. This will give you the board footage for a 1" thickness. If the material is 2" thick multiply the result for 1" by 2...and so on. If you’re looking for a good board footage calculator go to here.  A final note of board footage, board footage is determined by how the material starts, not how it finishes. For instance, if I start with a 2” thick piece of lumber and a customer wants it surfaced to 1 5/8” in final thickness, the board footage is determined by the board starting at 2” thick not at 1 5/8” as it finishes.

Sapwood/Heartwood

The most desirable portion of a tree differs depending on the species of wood that you are dealing with.  For instance with maple, the most desirable portion of the tree is the outer layer of the log that is tan to khaki in color and called sapwood.  The inner portion of a maple log is the less desirable portion of the log and called heartwood.  Heartwood in maple can be green, black, red, dark tan and is generally less dense, holds more moisture and can result in drying cracks during the prying process.  Most of the maple I sell is at least sapwood one face with the possibility of some heartwood on the second face.  In other species of wood like Walnut, Oak and cherry the heartwood is the most desirable portion of the tree.  The sapwood in these trees is often a thin layer on the outside of the log and is generally a creamy white to yellow color.  There is nothing wrong with this portion of the material other than it is a different color and will stand out from the rest of the same color material.

  • 4/4, 5/4, 6/4, 10/4, 12/4 Thicknesses

    All rough lumber from the mill is measured in 1/4" increments. That is to say that 4/4 means 1" thick material5/4 means 1/1/4" thick material....an so on. Material is generally expected to end up ¼” less than it originally starts.  4/4 material is expected to end up ¾” thick after surfacing; 8/4 at 1 ¾” in thickness and so on.

  • Defects as the result of improper drying:

  • Bowing

    Bowing in rough lumber occurs when wood curves along its length relative to its face.  Rather than lay flat on a surface the center of the board is raised up so that only the ends are touching.  This generally occurs from improper drying technique.  Not enough stickers to support it; drying too fast; or not having enough weight on the piece to keep it flat as it loses moisture.  Nearly all lumber has some degree of minor bowing which can be removed to achieve a flat board.  If the bowing is severe enough you will need to cut the board in half, thirds or quarters to get flat results.  

    Twist

    Think of twist in a board as you would if you took a wet towel and twisted it to wring the water out of it.  Rather than the towel laying flat, it is shaped in more of a cork screwed fashion with one end of the board being raised up and the opposite end of the board being pushed down.  Just about all rough lumber has some degree of twist and it absolutely can be removed to achieve a flat board contrary to popular belief.  

    Cupping

    Cupping is the result of trying to dry lumber faster than the moisture can be released.  It happens more often in wider lumber (over 9” in width) or in lumber that is more dense like hard maple, oaks, etc.  Time is literally money in a kiln so producers try to push the envelope as much as possible to get lumber dried and sold.  Cupping occurs across a board’s width taking a flat board and pulling the edges up to create a bowl type shape.  

    Crook

    We’ve all used the term crooked and that’s just what crook means in lumber.  Rather than having a nice parallel and straight board, a board will curve to the left or to the right like a winding road.

  • Natural defects listed in order of prevalence:

Worm hole

Worm holes come in two kinds – with an associated mineral streak or without the mineral streak.  Worm holes occur in just about all types of lumber from some insect burrowing through the tree and creating a small hole.  When that occurs, the tree tries to heal itself and it creates a brown mineral stain surrounding the hole.  In maple you’ll see a 1/16” sized hole with a mineral streak of varying lengths coming off of it.  Worm holes without mineral streaking occur either when a log is waiting to be run into lumber or after logs are cut into lumber and a pest burrows through the wood and creates a small hole.  Kiln drying will kill the pests if present, but the holes remain.

Mineral streaks

Mineral streaking usually appears when a tree has been damaged and it is trying to heal itself.  They can result from things like worms and pests, nails, bullets, and other forms of trauma.  


Bark inclusions

Bark inclusion strips & Bark Pockets – A bark inclusion is ingrown bark in a piece of lumber.  Bark around a tree undulates in thickness and depth and while most bark is removed when turning a log into a cant, occasionally bark can go deeper in some areas than others or it has a fold that projects down into the log.  A bark inclusion strip is a line of ingrown bark in a piece of lumber that is almost grown closed but shows as a narrow crack surrounded in bark.  If it’s more than an inch or so long I call it a bark inclusion strip.  Bark pockets are more of a circular area that has ingrown bark.

Wane

In simplest terms, wane is missing material along the edges of a board.  After a round log is turned into a square cant, it starts being cut into pieces of lumber and typically wane will occur in some fashion on the first cut or two off the cant.  Rather than a board having two nice square parallel edges there can be a rounded over portion of the edge that reduces the usable width of the board and that’s wane.

Dog Mark

Dog Marks

During the process of taking a round log and either turning it into a cant or processing it for lumber there are hydraulic “fingers” that will extend, bury themselves into the log and hold it in place as the saw blade passes through the log.  The fingers are called dogs.  After a side has been squared or the lumber has been cut the dogs will release, the log is rotated to the next side and the dogs will again grab the log and hold it while it is again squared or cut.  These dogs can exert enough force that they will leave pressure cracks or dog marks in the first piece of lumber cut off the log.  They are usually 1” to 2” in length and will usually be about 1/8” to ¼” deep but can occasionally go all the way through a piece of lumber.

Knots, Knot Pockets, Pin Knots

Knots are the result of branches coming off of the tree and being exposed when the log is cut into lumber.  There can be open knots – a portion of the knot is missing or has cracked out- and closed knots- the entire knot has survived the cutting and drying process and is 100% intact and smooth.  Knot pockets are typically only present on one face of the lumber and the knot has cracked out of the wood leaving an empty round hole or pocket.  Pin knots are generally knots that are less than 3/16” and can go all the way down to a pin prick in size.  I do not consider pin knots as a defect and will only mention them if there is a large patch of them or they are present over most of the material.  Most of the lumber we deal in is FAS so there are few knots present or we cut them out but some lumber like Walnut and Oak have a greater prevalence of knots.


Gum Pocket

Gum pockets only exist in Cherry lumber.  When a black cherry is damaged it oozes sap out of the tree that will cover the damaged area and thicken over time into a sticky gummy substance.  Over time it will eventually harden and bark will grow over it which leaves a pocket with the hardened gum inside.

  • Less Common Defects:

Sticker Stain and Drying Stain

When lumber is cut from the log it contains a high amount of moisture so it is placed in open stacked piles with narrow strips of wood evenly spaced across the face of the lumber in between the different tiers of the stack.  These are called stickers and their main job is to help increased air flow move through the stacked lumber to assist in releasing moisture.  Occasionally, moisture can get trapped under one of these stickers and will mildew which will cause a gray mildew stain on the lumber.  In lighter colored lumber like maple, ash or poplar, it will look like a gray line across the board that can penetrate 3/16” or more into the lumber.  Sometimes it comes off during surfacing and sometimes it doesn’t.  Drying stain is similar to sticker stain as it will appear as grayish discoloration on the material but it is a result of an issue during the drying process.  It can appear as just spots on the face of the lumber that will surface out or it can be contained within the core of the board and stain the entire board gray.

  • Pith

    Pith is the central canal through the center of log that is about 1/8” wide.  It will look like a drinking straw cut in half on the face of the lumber and is usually only present on lumber that comes from the heartwood of a log like walnut, cherry or oak.

Delamination

This can occur from internal drying cracks in lumber, shake, end checking or a grown over defect in the log and represents a separation of wood fibers within the material.  It will appear to be solid but as the material is surfaced an area will typically crack out from the vibration of the knives going over it.  In the attached pic you can see a chunk has delaminated from the end of this piece of cherry.

Bullets and Shot Gun Pellets

These are always a surprise when they appear as there is typically no sign of them on the lumber until they pop out during surfacing.  I’m guessing a squirrel probably met its end on this hard maple tree as you can still see a few of the lead pellets left in the wood.

Burls/Swirls

Burls and swirls are typically small circular areas where the grain creates a small visual effect.  They will occasionally have a small pin-prick bark pocket in the center of them and other times not.  Unless there is a lot of these on a piece of lumber I don’t typically point them out or consider them a defect.

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