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Douglas Fir Facts

How Douglas Fir Makes the Grade

April 21, 2011 by | Jennifer | There have been 0 comments

We’re going to delve into the sometimes complicated world of grading Douglas-fir and other lumber. We all know about grades. In school, if you get an A, you’re the best of the best. But if you get a C, D or something lower, then you probably won’t be the valedictorian. In the lumber industry, grades don’t break down so simply. As it is in school, lot depends on who is handing out the grades and on what the purpose of the test was to begin with.

Wood grades are a way of letting consumers know that the wood they’re buying meets certain guidelines. In order for any agency to grade lumber, they must follow rules set by the American Lumber Standard Committee (ALSC), a government agency run through the Department of Commerce.

Underneath the umbrella of ALSC are numerous lumber grading agencies. When it comes to Douglas-fir, you’re going to see grades from agencies that specialize in softwoods from the western U.S., such as the West Coast Lumber Inspection Bureau or the Western Wood Products Association. These groups grade the lumber based on its intended use.

Douglas-fir that will be used for framing a house is called structural grade, and it’s subjected to intense tests to determine how strong and stiff each board is. Wood that will be used for things like paneling, flooring, and trim is called appearance grade, and as you might expect, that means it’s evaluated mainly on its looks.

Timber graders visually inspect Douglas-fir and other lumber, assigning it a grade based on its color, texture, and grain. “Clear” is a term you’ll hear a lot—that means the wood is virtually free from knots, streaks, nicks and gouges from mill machines, or other blemishes. In the highest-level grades, moisture content levels also play a role.

A "select" grade Douglas fir plank.

The most perfect boards are known as “Selects” or “Finish” grade boards. Within those “Select” and “Finish” the grades have different names depending on which agency graded them. In general, the higher the letter grade, the less-knotty and more even in color it will appear.

Boards labeled “Superior” “B & BTR” (BTR=better) or “C & BTR” are almost knot-free and evenly colored. “Prime,” “D Finish” and “E” Finish are still mostly clear, but might have some variation. AltruFir’s CVG Douglas fir flooring is a C & BTR grade, and is characterized by having 10-25 rings per inch and knots no larger than ¾” in diameter. B & BTR is not commonly sold in the U.S., as there is little market for it, but it is available.

Anything within the “Select” and “Finish” categories makes good flooring, trim, cabinets, and paneling. There will be minimal color contrast, making each board look similar to another, which is good if you want your trim or paneling to have a formal, perfectly-matched look.

“Select Merchantable” and “Common” grades have some small, tight knots visible. These grades can also be used for flooring, paneling or siding—it just depends on the look you’re hoping to achieve. Some designers and home owners like the character of a knotty Douglas fir, while others prefer each board to look smooth and uniform.

flat sawn douglas fir

Knotty, or rustic, Douglas fir is often used for paneling.

“Construction” and “Standard” grade boards are going to have varying sizes of knots or knot holes, and are fine for fencing, shelving, sub-floors, or other uses where being pretty isn’t so important.

“CVG” is another acronym you will see in wood grading—it stands for Clear Vertical Grain, and it has to do both with the way the wood grows and the way it was cut. In the simplest of terms, the grain of the wood is the pattern of alternating light and dark rings that develop as a tree grows. When a tree is cut down and sawn into boards, those bands of color become visible. When the cells of a tree grow in just one direction, up and down the trunk of the tree, that’s a straight grain, and it’s something Douglas-fir in particular is known for.

The way the mill saws the wood affects what type of grain you see as well. We talked about this in our post about flat- vs. quarter-sawn lumber. Douglas-fir is known for exceptionally straight vertical grain, which makes it very good for flooring. When vertical grain boards contract and expand, as all wood does, they shrink less than a flat-sawn board and remain more stable. And even when they do contract, they contract evenly across the thickness of board, with minimal warping. Vertical grain boards in general stay flat, which is why it is a common choice for flooring.

Grain also has to do with the type of cells in the wood—when you cut a tree into boards, the cells that were once used to transport water up and down the trunk are visible as tiny hollows called pores. Woods with large pores are called open grain, while those with pores too small to see with the naked eye are called closed grain. In general, conifers like the Douglas-fir have small pores, and therefore a closed grain.

The texture of the wood plays a part too; wood with very small cells will be very smooth to the touch, and referred to as fine-grained, while a less-smooth wood with larger cells would be coarse-grained. Douglas-fir is a medium grained wood.

In the end, the grade your board gets doesn’t matter so much as whether it’s suited for what you want it to do. A high-grade “select” board might be perfect for a glossy china cabinet, while “common” grade boards with visible knots might be perfect for adding contrast and interest to a room-size batch of flooring. So don’t worry if your Douglas fir didn’t get straight A’s. Just because it’s a B, C, or D doesn’t mean it won’t meet the qualifications for your project.

- Jennifer Rouse


This post was posted in All Entries, Douglas Fir Flooring, Douglas Fir Trim and was tagged with Douglas fir flooring, douglas fir floors, fir flooring, grading douglas fir, douglas fir grade

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