Black walnut hardwood floors, rich color on a softer wood

Black walnut at a glance

Janka hardness

1,010 (softer than red oak at 1,290; about a quarter softer than white oak)

Typical cuts

Plain sawn for the broad ribbon grain; some quartered for straighter lines

Common widths

4 to 7 inch plank; wider in engineered; also stair treads, borders and inlays set into oak floors

Finishes it takes

Clear finishes almost always; water-based keeps the purple undertone, oil-based warms it; hardwax oil suits it well

Color and grain

Deep chocolate heartwood with purple and gray tones; pale sapwood unless steamed; ribbon grain

Minnesota seasons

Moderate movement, similar to oak; the dark color makes winter gaps more visible than they are

Where it is used most

Formal rooms, studies, bars and lounges, stair treads, inlays and medallions

What a black walnut floor looks like finished

A clear-coated walnut floor is deep brown with purple and smoky gray running through it, and the ribbon grain catches light differently from every angle. Water-based polyurethane holds that cool, almost plum undertone; oil-based warms the floor toward red-brown and deepens it. Hardwax oil gives a low, matte surface that suits walnut especially well and is easy to spot-repair, which matters on a species that dents. Walnut sapwood is nearly white, so unless the boards are steamed at the supplier to even the color, a natural-grade walnut floor carries pale streaks.

Hardness, dents and the honest case for walnut

Walnut is a softer wood than oak and no finish changes that. Finish protects against scratches and spills; dents come from the wood underneath compressing, and at 1,010 walnut compresses under heels and dropped objects that oak would not record. The homeowners happiest with walnut accept the dents as patina, keep it out of the kitchen and mudroom, or both. Where the color is the whole point of the room and traffic is light, nothing else gives that depth without stain. Where the room is the busiest in the house, stain white oak dark instead.

Black walnut through a Minnesota winter and summer

Walnut moves about as much as oak through the humidity swing, so a solid floor gives up a little width in January and takes it back in July. The difference is visibility. A hairline gap in a pale oak floor is a faint line; the same gap in walnut shows light subfloor through dark boards and reads as a crack. A humidifier on the furnace helps more than anything we can do at install, along with acclimation in the house and expansion room at the walls. Over radiant heat and in walkouts we install engineered walnut.

Where black walnut belongs in the house

Dining rooms, studies and formal living rooms, where the color sets the mood and traffic is light. Stair treads, where the wood is thick enough to take wear and the contrast against painted risers is sharp. Inlays and medallions set into white oak floors, which is how a good share of the walnut we handle gets used. Bars and restaurant dining rooms where the owner wants warmth and accepts maintenance. We would keep it out of kitchens with kids and out of mudrooms.