Lumber Grades Explained

FAS Walnut LumberHow many times have you visited the lumber yard not knowing exactly what pieces you will find and hoping that you can get lucky and get the pieces you need to build your project?  Walk into any lumber yard or look at a price list and you will see many terms like FAS, SAB, Select, Common, etc.  These are all grades of lumber each with a price point attached to it.  Certainly a better grade will get you clearer, more defect free lumber but understanding the grading guidelines will help you get the right dimensions out of your pieces too.

Until you get to the lumber yard to get your material, much of your design can be compromised because you can’t get the sizes needed.  Knowing what it takes to meet a lumber grade can help you plan your lumber purchases and design your projects to ensure you can get what you need.

FAS: First and Seconds

This lumber must be at minimum 6″ wide and 8′ long and 83% of the board must be free of defects.


This lumber must be at minimum 4″ wide and 6′ long.  It has one FAS face while the opposite face can be 1 Common quality.

Common 1, 2, & 3

The common grades follow the same pattern with decreasing percentages of clear area.  The minimum board size is 3″x4′ and clear percentage starts at 66% down to 50%.

Using the Grade to Choose Your Lumber

Defects include knots, splits, checks, bark inclusions, pith, wane, worm holes, decay, sticker stain from kiln drying.  Notice that sap wood is not considered a defect by the grading systems even though the general buying populace wants a heart wood only face.  Regardless each grade has a minimum board size so when designing your project cut list you can count on a certain width and length just by designating which grade you will buy.

For example:

I’m building a blanket chest with frame and panel construction.  Each side will have 3 panels plus one panel on each end.  I don’t want to glue up 8 different panels so if I design my chest so that the panels are 6″ or under I know I will be able to buy FAS lumber and make all my panels 1 piece.  Remember FAS lumber’s minimum size is 6″x8′ long.


I’m building a bookcase that is 12″ deep.  I would like to make each side from one board but I’m concerned I won’t be able to get 12″ wide stock from my supplier.  I know they always have lots of FAS stock so I can at least do a book match or sequence match from a thicker board to get the grain and color match of a single board.

Keep in mind that these grades specify the minimum measurement and wider and longer boards are always a possibility.  Possible doesn’t help you plan a project however.

So next time you visit your lumber dealer, pay close attention to what grades they normally carry.  Knowing what it takes to make the grade will give you a good understanding of the widths and lengths you can count on being available.  This will help you to better anticipate the sizes of lumber available while at the drawing board instead of hoping they will have the right sized boards when you show up.

One Response to “Lumber Grades Explained”

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  1. Kyle Winters says:

    Considering how confusing lumber grades can be, it is nice to have an article break this down for those of us not in the know. I didn’t know that the grade was based around the decreasing percentage of clear area. I’ll have to keep this in mind since my spouse wants to try and build a custom set of lumber cabinets for our home.

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