Grades of Lumber
Related Articles: Trellis, Plans/Kits, Building a Trellis
Lumber Grade Specifications
Just like any other product, lumber is graded. Different species have different systems but they are basically the same in many respects. The lumber is graded from the worst quality to the best. The grades will take into account the size and frequency of knots and the location of where the lumber comes from the tree. Grades often take into account the grain of the lumber as well.
Grain of lumber is called either vertical or flat. Flat grained lumber is generally considered lower quality. It has a greater tendency to cup or curl. You can easily spot a flat grained piece of lumber when you look at the cut end. If the growth bands are slightly curved or somewhat parallel with the width of the piece of lumber it is flat grained.
If the growth bands are parallel with the thickness the lumber is considered vertical grained.
Flat grained lumber should be used for the decking surface and stair treads. Always install it so the growth bands hump upwards towards the sky.
Vertical grained lumber is excellent for trellises and other things where warpage will cause appearance problems.
Redwood Lumber Grades
Construction HeartThis lumber is taken from the center of the tree (heart) and can contain knots. It is great for trellis posts or beams. The knots are usually small and tight.
Construction Common
This grade contains knots and can be taken from both the center or the outer fringes of the tree. If it is from the outer edges, it will be lighter (blond) and it is called sapwood. This grade should not be used where it might come into contact with the ground.
Merchantable Heart
This is an economical grade of heartwood. It can contain larger knots and knot holes.
Clear All Heart
This is is the second best grade. It contains no knots and is taken from the heart of the tree. This lumber has the highest amount of natural preservatives.
Architectural Grade
This is the absolute best grade. It is unequaled in beauty. If you want a piece of wood that has exquisite graining, will be warp and twist resistant, this is the one to purchase. It is expensive - don't waste it!
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