MAKING THE GRADE

By DANA SPESSERT, Chief Inspector

Over the past few years, there has been an increased demand for hardwood building materials, specifically in larger timbers. These timbers must make a certain grade to meet the designer’s strength ratings requirements. NHLA has grading Rules that meet or exceed the requirements of many of the design values necessary for projects, and many of these projects are replacements of older timbers for restoration.

This month I want to describe the first of these Rules, Select Dimension - Select Car Stock (Boxed Hearts & Planking), or as I like to call it, “The FAS of Timbers.” On page 65 of the NHLA Rules Book, under the heading “Select Dimension – Select Car Stock,” you can find the entire Rule. For the purpose of this article, I will summarize the Rule.

1. Square Edges, except: a. Wane not over ¼ width of surface it appears on, on one corner or amount divided and show on more than one corner b. Pieces 5” and less thick, wane admitted (no more than 20% of shipment). i. 1/3 width ii. 1/3 thickness iii. 1/3 length in the aggregate.

4. Sound Knots Limitations: a. Not exceeding ½ the width of the surface, minimum of 6’ apart. b. Less than ½ to 1/6 the width of the surface in average diameter, minimum of 12” apart. c. Less than 1/6 the width of the surface, unlimited.

5. Unsound Knots and/or Holes Limitations: a. Minimum 6’ apart. i. Less than 6” thick - ½” average diameter. ii. 6” to 10” thick - 3/4” average diameter. iii. 11” and thicker - 1 ¼” average diameter.

6. Pith Limitation: a. Boxed pith admitted without limit. b. Exposed firm pith admitted 1/3 the length on one face.

7. End Shake Limitation: a. Not over two annual growth rings, confined within end. b. Maximum length = 1/4 circumference of shake ring. c. Cannot extend to two faces.

8. Surface Shake Limitation: a. 1/12 of the length of the piece in the aggregate.

2. Size: a. 10% may be ¼” scant in thickness and/or width. b. 100% may be up to 1” over in thickness and/or width. c. No more than 3” overlength.

3. Will admit stain, ordinary season checks, bird pecks, pin worm holes, spot and shot wormholes.

9. Split Limitation: a. Shall not exceed 12” in length in either end of the piece of Standard or specified length.

If you have any questions please reach out to me at d.spessert@nhla.com or 901-399-7551.