Black Walnut Lumber: Sapwood Rules, Steaming and Grades

Black walnut lumber is graded under NHLA rules that are modified for walnut: boards may be narrower and shorter, clear cuttings smaller and sapwood is admitted without limit. Most of it is sold unsteamed and unselected for color in 4/4 to 8/4, with steamed stock from specialist producers. A buyer who wants heartwood only, wide boards or long clear lengths has to say so on the order.

Item	Typical for black walnut lumber
Species	Juglans nigra
Grading	NHLA rules with walnut modifications: smaller boards and cuttings, sapwood admitted without limit
Color	Heartwood light to dark brown, sapwood nearly white and up to about 3 in wide in open-grown trees
Steaming	Generally sold unsteamed. Steamed stock from specialist producers
Common thicknesses	4/4, 5/4, 6/4, 8/4, 10/4
Average board size	4 to 8 in wide, 6 to 12 ft long
Side hardness (Janka)	about 1,010 lbf at 12% moisture
Specific gravity	0.51 green, 0.55 at 12% moisture
Shrinkage, green to oven dry	radial 5.5%, tangential 7.8%, volume 12.8%
Heartwood decay resistance	Resistant (Wood Handbook group)
US tariff line	4407.99, statistical line for walnut

Values are typical for the species from the USDA Wood Handbook and the NHLA species guide. They are not guarantees for a lot. The NHLA rulebook governs grades.

Why walnut has its own rules

Walnut does not grow in stands like oak. It grows as scattered, often open-grown trees with short clear trunks and a wide band of sapwood. The NHLA species guide gives US walnut growing stock as 137.8 million cubic meters, about 0.9% of all US hardwood growing stock. If walnut were graded on the standard rule, little of it would make the top grades.

The NHLA rules are therefore modified for walnut. The species guide sums up the effect: smaller specifications, smaller clear cuttings and sapwood admitted without limit. Extension summaries of the rules note, for example, that walnut FAS admits boards from 5 in wide and boards 6 and 7 ft long, which the standard FAS rule (6 in and 8 ft minimum) does not. Read the walnut section of the current rulebook for the exact figures in your contract.

Point	Standard NHLA rule	Walnut
FAS minimum board	6 in wide, 8 ft long	Narrower and shorter boards admitted (summaries cite 5 in and 6 to 7 ft, check)
Clear cutting sizes	4 in x 5 ft or 3 in x 7 ft for FAS	Smaller cuttings admitted
Sapwood	Not a defect in most species	Admitted without limit
What the buyer gets	Long, wide clear boards in FAS	Shorter, narrower boards, sapwood on edges

Two practical consequences follow. First, a walnut FAS price cannot be compared directly with an oak or cherry FAS price, because the boards are not the same. Second, a cut list built for oak needs to be checked against walnut sizes. Our FAS grade page shows the standard rule and the lumber grades hub lists all grades.

Sapwood, color and steaming

Because sapwood is not a defect, a typical walnut board has pale edges on a brown heart. Buyers handle that in three ways:

Option	What you order	Effect on price and supply
Accept sapwood	Standard grade, unsteamed	Widest choice, lowest walnut price
Steam the lumber	Steamed walnut, sapwood admitted	Sapwood darkens toward the heart color, heartwood tones even out
Limit sapwood	Grade plus a written sap limit, such as heartwood one face or a percentage	Smaller choice, higher price, more waste at the mill

Steaming is done on green lumber in a closed chamber before kiln drying. The NHLA guide says specialist producers offer steamed walnut to darken the sapwood. It does not turn sapwood into heartwood, and very pale sapwood may still show under a clear finish. Unsteamed walnut keeps a lighter, more varied heartwood with purple and gray tones that many furniture makers prefer. Our guide to steamed vs unsteamed walnut compares the two in finish samples.

Write any color rule in measurable words. “Sap one face only”, “heart one face, sap on the back allowed” or “sapwood not over 10% of the face” can be checked at the yard. “Good color” cannot.

Yield, sizes and thickness

The NHLA guide lists average walnut boards at 4 to 8 in wide and 6 to 12 ft long. That shapes how walnut is used:

• Short parts first. Drawer fronts, frames, legs and short rails come out of walnut boards with little waste. Long table tops need FAS boards sorted for length, often at a premium.
• Wide boards are rare. Wide, clear walnut is sold as a sort with its own price. Glued panels from narrower boards are the usual answer.
• Thick stock exists. 8/4 and 10/4 are common enough for legs and solid tops, more so than in cherry.

Grade by part matters more in walnut than in other species, because the grade price steps are large. Many shops buy No.1 Common walnut for short, narrow parts and keep FAS for long rails and tops. Run a yield test on a small lot of two grades before a large order.

Properties that matter to a buyer

Property	Black walnut	Black cherry	Hard maple (sugar)
Side hardness at 12%	about 1,010 lbf	about 950 lbf	about 1,450 lbf
Specific gravity at 12%	0.55	0.50	0.63
Modulus of rupture at 12%	about 14,600 psi	about 12,300 psi	about 15,800 psi
Tangential shrinkage	7.8%	7.1%	9.9%
Heartwood decay resistance	Resistant	Moderately resistant	Slightly or not resistant

Values are from the Wood Handbook tables for clear wood. The Handbook describes black walnut as normally straight grained, easy to work with tools, stable in use and well suited to natural finishes. Weight from these figures: walnut at 12% moisture is near 38 lb per cubic foot, or a little over 3 lb per board foot. Use the supplier’s weight for freight.

Where walnut is used

Use	Grade usually quoted	Note
High-end furniture	FAS and No.1 Common, steamed or not	Grade by part, color agreed
Cabinets and doors	No.1 Common and F1F	Short and narrow parts
Architectural woodwork and paneling	FAS, color sorted	Consistent heartwood
Gunstocks and turnings	Thick stock, select figure	Special sorts
Flooring	Common grades	Character marks accepted

What to write on the RFQ

A walnut quote needs more lines than an oak quote because the defaults are looser. State the species, grade and rulebook, steamed or unsteamed, sapwood rule, thickness, minimum width and length if your parts need them, drying, board feet and paperwork. Our hardwood lumber specifications guide explains every field.

RFQ line: Black walnut (Juglans nigra), FAS and No.1 Common, NHLA walnut rules (edition named), steamed, sapwood one face allowed, 8/4 rough, KD 6-8%, 5 in and wider, 6-12 ft, 1,500 BF, Lacey Act data.

Send it through our lumber RFQ form and we pass it to up to 3 mills or yards that stock walnut in that grade. For other species see the hardwood species hub.