SPF Characteristics 101: Knots and Wane

A knot is a portion of a branch or limb that has become incorporated in a piece of lumber.  Knots are classified as to form size, quality, and occurrence.  [Standard Grading Rules for Northeastern Lumber para. 718.0]

An Encased Knot is one that results from a dead branch which the wood growth of the tree has surrounded.  [Standard Grading Rules for Northeastern Lumber para. 718.0 (b)]

A Spike Knot is produced when the limb is cut either lengthwise or diagonally.  [Standard Grading Rules for Northeastern Lumber para. 78.0 (e)]

An Edge Knot is any knot that visibly occupies 50% or more of a narrow face (1/2 the thickness), or the knot visibly displaces wood extending from one narrow face to the opposite narrow face.  (The same knot is visible on both narrow faces).  Knots visible on all four faces are considered Edge Knots.

Note:  In cases where there is not a defined “narrow face” such as a 4×4, the narrow faces are determined at the grader and/or inspector’s discretion.

Additional instructions regarding Edge Knots and their application in the grading process will be discussed in SPF Level 200 Courseware.

A Centerline Knot is any knot in which the mid-point (pith-center) of its displacement is located directly in the center of the piece of lumber.

Additional instructions regarding Centerline Knots and their application in the grading process will be discussed in SPF Level 200 Courseware.

An Elsewhere Knot is any knot in which the center of its displacement (Pith-Center):

• is not located true to the centerline of the piece of lumber, and
• the knot does not visibly occupy 50% or greater of a narrow face, and
• the knot is not occupying both narrow faces.

Additional instructions regarding Elsewhere Knots and their application in the grading process will be discussed in SPF Level 200 Courseware.

A Sound Knot contains no decay.   [Standard Grading Rules for Northeastern Lumber para. 718.0 (j)]

A Pith Knot is sound in all respects except it contains a pith hole not over 1/4″ in diameter.  [Standard Grading Rules for Northeastern Lumber para. 718 (k)]

An Unsound Knot contains decay  [Standard Grading Rules for Northeastern Lumber para. 718.0 (m)]

Tight Knot – a knot so fixed by growth, shape or position that it retains its place in the piece.  [Standard Grading Rules for Northeastern Lumber para. 718.0 (o)].

Loose Knot – a knot not held tightly in place by growth, shape or position.  [Standard Grading Rules for Northeastern Lumber para. 718.0 (s)].

Fixed Knot – a knot that will retain its place in dry lumber under ordinary circumstances, but is movable under pressure (commonly referred to as a clicker) though not easily pushed out.  [Standard Grading Rules for Northeastern Lumber para. 718.0 (t)].  These are commonly referred to as “a clicker.”

Firm Knot – a knot that is solid across its face, but contains incipient decay.  [Standard Grading Rules for Northeastern Lumber para. 718.0 (n)]

Wane is the appearance of bark or lack of wood from any cause, except eased edges, on the edge or corner of a piece of lumber.  [Standard Grading Rules for Northeastern Lumber para 750.0]