Timber Products Inspection Grading Guidelines
Log Grading Guidelines
Why its importrant to use premium Graded Logs
In the mid 1970’s, Timber Products Inspection was approached by members of the log home industry and related regulatory groups and asked to increase our scope of auditing services to cover grading needs for building logs for both residential and commercial uses. Timber Products answered that need and now provide a nationwide grading and grade stamping program to log home manufacturers. Their grading rules and related design values are based on the nationally recognized standard ASTM D3957 (Standard methods for Establishing Stress Grades for Structural Members Used in Log Buildings). A long time industry leader, TP’s log grading program is accepted by the International Code Council and the US Department of Housing and Urban Development.
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TP also offers these value added services:
- Lot or individual home inspection grading services for homeowners, builders, or manufacturers with smaller production levels.
- Engineering services which provide TP’s in-house structural design expertise to homeowners, builders, and manufacturers.
- Training services for manufacturers, individuals, or groups to gain additional skills.
Wall Log Grades
| DEFECT | PREMIUM | SELECT | RUSTIC | WALL LOG 40 | WALL LOG 30 |
|---|---|---|---|---|---|
| Decay | none | none | none | 1/6 X 8" | 1/6 X 8" |
| Insert Hole | less than 1/2" | less than 1/2" | less than 1/2" | less than 1/2" | less than 1/2" |
| Check | 1/2 dia | 1/2 dia | 2/3 dia. | 2/3 dia. | 2/3 dia. |
| Shake | 1/16" | 1/3 dia. | 1/2 dia. | 1/2 dia. | 1/2 dia. |
| Slope | 1 in 12 | 1 in 10 | 1 in 8 | 1 in 6 | 1 in 6 |
| Split | =width | =width | 2X width | 2X width | 2X width |
| Knot Size | 30% | 38% | 45% | 65% | 65% |
Cross section: in 6" length knot size not to exceed 2X allowable centerline knot allowance.
Wane: Not to exceed 1/4 diameter all grades.
Timber NONE all grades Breaks:
Round Log Grades
| defect | UNSAWN ROUND | SAWN ROUND #1 | SAWN ROUND #2 | SAWN ROUND #3 |
|---|---|---|---|---|
| Decay | none | none | none | 1/10 X 8" |
| Insert Hole | 1/4" | 1/4" | 1/4" | 1/2" |
| Check | 1/2 dia | 1/2 dia | 1/2 dia. | 2/3 dia. |
| Shake | 1/6 dia | 1/6 dia. | 1/6 dia. | 1/2 dia. |
| Slope | 1 in 16 | 1 in 14 | 1 in 10 | 1 in 6 |
| Split | =width | =width | =width | 2X width |
| Knot Size | 1/2 dia | 1/3 dia | 1/2 dia | 3/4 dia |
Cross Section:Cumutitive total of knots in any 12" of length not to exceed diameter
Wane: Not to exceed 1/4 diameter all grades
Timber: NONE all grades Breaks:
Sawn or shaved: Sawn Round grades, not exceed .3 of radius
Radius = 1/2 diameter Example: a 10" log could remove 1.5", finish size should be 8.5"