Walnut Lumber

Walnut is the one common domestic hardwood that shows up dark chocolate brown right off the saw — no stain required. The sapwood is creamy white, while the heartwood is light brown to dark chocolate brown, making the difference in color quite distinct. That’s the whole appeal, and the whole catch. You’re paying for the heartwood, and you need to understand grade, sapwood, and waste before you ever pick up a board.

Here’s the short version. Walnut lumber constitutes less than two percent of all hardwood lumber produced. It’s a premium, specialty wood — right for high-end furniture, cabinets, and showpiece millwork, wrong for anything you plan to paint or frame a shop with. Walnut is considered one of the supreme species for high end furniture, cabinets, doors and interior joinery. It is used for flooring and panelling and it is widely used to contrast with other hardwoods.

Western Building Center carries it as a 4/4 walnut board, surfaced two sides (S2S) — a one-inch nominal board dressed flat on both faces so you can read the grain and color before you mill it.

What Walnut Is and How It Works

Walnut (Juglans nigra) is an eastern and central U.S. hardwood, not a Montana native, so it arrives here as kiln-dried stock. Black walnut ranges from the east coast to the great plains and from Texas and Georgia north to central Minnesota, Wisconsin, Michigan, and southern Ontario. Most of the best quality trees are found in the central states region from Ohio to Iowa.

It’s a medium-density wood that punches above its weight. At 12 percent moisture content, walnut weighs about 38 pounds per cubic foot, making it an intermediate weight species. For its weight, it is a relatively strong wood. On the Janka scale it sits at 1,010 — harder than poplar or pine, softer than the oaks. That puts it in a comfortable middle ground for furniture and cabinetry.

The reason walnut earns its keep at the bench is workability. It works easily with hand and machine tools, and nails, screws, and glues well. It holds paint and stain very well for an exceptional finish and is readily polished. For turning and boring it’s in a class of its own — walnut is rated as intermediate in planing, but it is a good wood for shaping and the best of any commercial hardwood species for turning and boring.

It also stays put once it’s built. It has good dimensional stability. That matters in Montana’s dry, heated interiors, where a less stable wood will fight you across the seasons. The flip side: it dries slowly, and care is needed to avoid kiln degrade. That’s the mill’s problem if you buy properly dried stock, but it’s worth knowing if you ever source green or air-dried boards.

One bonus most buyers never use: the heartwood of walnut is rated as resistant to very resistant to decay. Walnut was tough enough that it was also commonly used for construction purposes, such as barn timbers. Even as late as the 1960s the author witnessed the sale and use of walnut 1 x 12s for hayrack boards because it would not rot. Nobody’s building hayracks out of it now — it’s far too valuable — but the toughness is real.

Property	Value
Scientific name	Juglans nigra
Janka hardness	1,010 lbf
Specific gravity (density)	0.56
Dried weight	~3.2 lbs/bdft (~38 lbs/cu ft at 12% MC)
Bending strength (MOR)	14,600
Bending stiffness (MOE)	1,680
Radial shrinkage	5.5%
Tangential shrinkage	7.8%
Heartwood decay resistance	Resistant to very resistant

Grades, Sizes, and the Board-Foot System

This is where walnut trips up buyers coming from softwood dimensional lumber. You don’t buy it by the 2x4. The unit of measure for sales and purchasing of hardwood lumber is a board foot. And the grading rules aren’t built to use the whole board — unlike softwoods, the hardwood grading standards are not written for the purposes of utilizing the entire board. The rules are designed for utilization of only the clear portions of each board.

Walnut gets its own modified version of the NHLA rules. The National Hardwood Lumber Grades for walnut and butternut are distinctly different than the standard grades that generally apply with slight modification to other species. Short lengths are accepted in the top grades of walnut; some short boards are graded by counting defects, minimum board widths for the top grade are narrower and the size of cuttings are smaller. The practical takeaway: any one grade in walnut will appear to be of lower quality when compared to lumber graded by the “standard rules.” Don’t let that fool you. It’s the species, not the board.

The three commercial grades you’ll actually shop:

Grade	Clear yield	Minimum board	Typical use
FAS-F1F	83%+ defect-free	5” wide × 6’ long	Table tops, moldings, wide-plank flooring
No. 1 Common	66%+ defect-free	3” wide × 4’ long	Cabinets, chairs, medium furniture parts
No. 2 Common	50%+ defect-free	3” wide × 4’ long	Strip flooring, plaques, small parts

The grade of FAS-F1F will have the highest percentage of clear areas in the pieces, 83 percent or more defect-free area. The minimum size clear areas used for calculating this grade are 4 inches wide x 3 feet long, or 3 inches wide x 6 feet long. FAS-F1F is typically used for table tops, moldings, wide plank flooring, and other uses that require larger areas of clear wood. Step down a grade and No. 1 Common will have a clear area percentage of at least 66 percent defect-free wood in each piece. The minimum size clear areas are 4 inches wide x 2 feet long, or 3 inches wide x 3 feet long. This grade is typically used for cabinets, chairs, and other medium size furniture parts.

The buying logic is simple. Showpiece tops and panels that need long, clear runs — go FAS. Smaller parts where you’ll cut around defects anyway — No. 1 Common works fine, since you’re trimming off the rough spots regardless.

On sizes, walnut comes in a stack of rough thicknesses. Most grades of lumber are commercially produced in standard rough thicknesses including 4/4 (1 inch), 5/4 (1-1/4 inches), 6/4 (1-1/2 inches), 8/4 (2 inches), 10/4 (2-1/2 inches), 12/4 (3 inches), 16/4 (4 inches) and 20/4 (5 inches). Western Building Center’s walnut comes as a 4/4 board surfaced two sides — the one-inch workhorse for most furniture and cabinet work.

Width and length aren’t fixed. There are no standard width sizes for hardwood grade lumber, rather each piece is produced as wide as the timber allows and is sold as a random width product. Typical grade lumber bundles will have a variety of widths which will be measured and sold by the inch in width x the length of each piece. Expect common thicknesses of 4/4 through 10/4, average board width of 4” to 8”, average board length 6’ to 12’, and average dried weight around 3.2 lbs/bdft.

You can buy it rough or dressed. This lumber is typically kiln dried to an average moisture content of 8 percent so it can be utilized in all climate-controlled environments. Many producers also offer surfacing and ripping services for their lumber. S2S, like the WBC board, gives you two flat faces while leaving the edges for you to joint.

Heartwood, Sapwood, and the Steaming Question

The dramatic color split catches first-timers off guard. The dark chocolate is the heartwood — that’s what you’re paying for. The creamy white edge is sapwood, and it’s not a defect, but it changes how much usable dark material you get.

That’s why most commercial walnut is steamed. The commercial industry steams walnut lumber while it is still green. This process darkens the sapwood to appear more like the heartwood, and at this point the sapwood is not considered a defect. Steaming does double duty — it also tends to make the heartwood more uniform in color and eliminates any purplish cast that can occur. In the grading rules, steam treated sapwood is allowed without limit in all grades.

Not all walnut is steamed, though, and it’s worth asking. The lumber is generally sold un-steamed and unselected for color. Specialist producers may offer steamed walnut intended to darken the sapwood and thus reduce the color difference between heartwood and sapwood. If color uniformity matters to your piece, that’s a question to settle before you buy, not after you’ve milled.

Plan your material with waste in mind. Budget 20 to 30 percent on a furniture project to cover sapwood and defects — the grading system assumes you’re cutting around the rough spots, so buy more board footage than your finished part list says you need.

Choosing Walnut Over the Alternatives

Walnut earns its premium where the wood is the show. Furniture, cabinets, doors, architectural millwork, flooring, paneling, gun stocks — anything where the deep color and grain carry the design. The heartwood is typically a beautiful chocolate brown color, which is not duplicated by any other species. Nothing else domestic gives you that without a stain can.

Where it doesn’t earn its keep: anything headed for paint, or any large utility build. You’re burying that chocolate heartwood under primer — a waste of money and a waste of wood. For painted work or rough framing, cheaper species do the same job.

And walnut plays well with others. It is a favored wood for use in contrast with lighter-colored species. Pairing it with a paler wood for contrast is a classic move that also stretches your walnut across a project.

Installation and Finishing Basics

The first rule for any imported hardwood landing in a dry Montana shop: let it settle. Walnut’s tangential shrinkage runs 7.8 percent, so it moves with moisture, and your heated interior is a lot drier than wherever this board was kilned. Acclimate it flat-stacked in the shop for at least two weeks before you mill, and aim for an interior moisture content around 6 to 8 percent. Kiln-dried walnut targets an average moisture content of 8 percent so it can be utilized in all climate-controlled environments — but if you bought air-dried or green stock, check it with a moisture meter before you commit.

At the machine, sharp carbide tooling matters — walnut’s natural oils will burn against dull edges. Pre-drill for screws to keep the wood from splitting. The good news on finishing: walnut needs no pre-conditioner. The wood is tight-grained and polishes to a very smooth finish. Prized worldwide for its deep rich color, additional staining and oiling will deepen the richness and natural characteristics of the wood. A natural oil or a clear film finish lets the grain do the talking.

For cabinetry, manage seasonal movement by design — pair solid walnut frames with walnut-veneered panels so the panels float and the whole assembly stays tight through the heating season.

Frequently Asked Questions

Why does walnut look like a lower grade than oak or maple at the same name? Because walnut is graded under modified rules. Short lengths are accepted in the top grades, minimum board widths for the top grade are narrower and the size of cuttings are smaller. As a result, any one grade in walnut will appear to be of lower quality when compared to lumber graded by the standard rules. The rules were built to squeeze the most usable wood out of a scarce, valuable species.

What does 4/4 mean? It’s the rough thickness in quarter-inches. 4/4 equals 1 inch, 5/4 is 1-1/4 inches, 6/4 is 1-1/2 inches, 8/4 is 2 inches, and so on. A 4/4 S2S board is a one-inch-nominal board dressed flat on both faces.

Is the white streak in my walnut a defect? No. That’s sapwood. The amount of white sapwood in younger, fast growth trees and open-grown trees such as yard trees can be substantial. Steaming darkens it, and in the grading rules the steamed sapwood is not considered a defect.

Why buy by the board foot instead of by the piece? That’s how hardwood is sold, and the grading reflects it. There are no standard width sizes for hardwood grade lumber; each piece is produced as wide as the timber allows and is sold as a random width product. You’re buying volume of clear wood, not a fixed dimension.

Can walnut handle flooring in a busy room? Yes. Walnut flooring transforms spaces into showcases of luxury. Its rich color, distinct grain pattern, and exceptional hardness that can withstand the demands of high-traffic areas makes it an excellent choice for flooring. At 1,010 Janka it’s plenty for residential floors.

Should I worry about it moving after it’s built? Less than with most woods. It’s favored for its bending properties and stability in furniture, flooring, and cabinetry, maintaining shape and smoothness over time. Acclimate it first and design cabinet panels to float, and walnut behaves through Montana’s dry winters.