Figure 4: SELECT STRUCTURAL Joists & Planks (38 through 89 mm thick x 38 through 337 mm wide, actual). Knots are limited to sound, firm encased and pith knots, if tight and well spaced, with one unsound or loose knot permitted per 1.2 m. Knot size (relative to centerline) and knot type (unsound or loose) are restricted in this high-strength grade. J&P and other Dimension grades are often manufactured S-DRY or KD.