2x6 Lumber

A 2x6 is a 2x6 until you try to build something with it. The board that frames a wall isn’t the one that sits on a deck, and neither is the one you’d want showing in a finished room. Pick by the job first, then the grade, then the length your cut list needs.

What a 2x6 actually measures

A 2x6 is the name, not the size. A surfaced 2x6 is 1-1/2 inches thick by 5-1/2 inches wide. Lay out your joints with those numbers. Wood also moves a little with moisture, so on a repair, measure the old framing before you cut; older lumber in a Montana farmhouse may not match today’s boards.

Framing: fir/larch, studs and MSR

Most framing 2x6s here are fir/larch, the Douglas fir and western larch that grow right here in the Northern Rockies. They’re stiff, strong framing lumber.

• No. 2 and Better fir/larch, 8 to 20 feet in 2-foot steps: the everyday framing grade for walls, rafters and joists that your plans call out as No. 2.
• Select Structural fir/larch, 8 to 20 feet: the top visual grade, for plans that specify it where spans and loads are higher.
• 1800F MSR fir/larch, 18 feet: machine stress-rated, meaning each board is tested for stiffness. Used where an engineer or a truss design calls for MSR.
• Precut studs: fir/larch at 92-5/8, 104-5/8 and 116-5/8 inches, and whitewood at 92-5/8 and 104-5/8. The precut lengths frame 8-, 9- and 10-foot walls with the plates, so you’re not trimming every stud.

Why 2x6 walls? A 2x6 wall has a deeper cavity than a 2x4 wall, so it holds more insulation, and that’s why so many Montana houses and shops are framed with them. The stronger studs can also allow wider spacing where the code and your design allow it, which means fewer studs and less framing bridging the insulation. Lining up windows and doors with the stud layout saves studs too.

Buy the grade the plans call for. Grade is about strength; a clean-looking board isn’t proof of it.

Outdoors: treated #2

Pressure-treated No. 2, CA-C .15, in 8, 10, 12, 14, 16 and 20 feet, is the 2x6 for deck framing, deck boards and other outdoor work. Treatment pushes preservative into the wood; it’s not a strength grade, so check both: the treatment for the exposure and the grade for the job. Use fasteners and hangers rated for treated lumber, and keep water from sitting on it. A treated board that stays wet still checks and cups.

Cedar

Cedar 2x6, S1S2E, in 8, 10, 12 and 16 feet, is for the outdoor work you’ll look at: fence rails, planter boxes, pergola parts, outdoor benches. S1S2E means smooth on one face and both edges, with the back left rough.

Interior woodwork: appearance-grade whitewood

Appearance-grade whitewood, 8 to 20 feet in 2-foot steps, is picked for looks: fewer knots and blemishes, for shelving, mantels, built-ins and anything you’ll see in a finished room. It’s for dry, interior use; whitewood left wet warps and can rot. For load-bearing framing, use a structural grade instead.

Whitewood is a lumber-trade name that covers several pale softwoods, and it can be hard to tell from pine by eye, so buy by the label, not the color.

Ceilings and floors: tongue-and-groove decking

2x6 tongue-and-groove whitewood decking #2, in 12 and 16 feet, has a tongue on one edge and a groove on the other so the boards lock together. It’s the board for exposed wood ceilings and roof decking over beams, a classic look in Montana cabins and great rooms, and for solid floors over joists.

Lengths and keeping them straight

2x6	Lengths
Fir/larch No. 2 & Better	8 to 20 ft, every 2 ft
Fir/larch Select Structural	8 to 20 ft, every 2 ft
Fir/larch 1800F MSR	18 ft
Precut studs	92-5/8, 104-5/8, 116-5/8 in.
Treated No. 2	8, 10, 12, 14, 16, 20 ft
Cedar S1S2E	8, 10, 12, 16 ft
Appearance whitewood	8 to 20 ft, every 2 ft
T&G whitewood decking	12, 16 ft

Group your cuts by length before you buy, and allow for the saw kerf. The longest board is only the better buy when your cuts use it.

Lumber stays straight if you store it right: flat, supported every few feet, off the ground, under cover and with air moving through it. Through a Montana winter, a stack left on wet ground or under a sagging tarp will twist and crack before you cut it.

The Pick

For wall framing, No. 2 and Better fir/larch or the precut studs; Select Structural or MSR where the plans call for them. For decks, treated No. 2. For outdoor woodwork you’ll see, cedar. For shelving and trim work inside, appearance whitewood. For a wood ceiling, the tongue-and-groove decking.

Frequently Asked Questions

What is the actual size of a 2x6?

1-1/2 inches thick by 5-1/2 inches wide, surfaced.

What 2x6 should I use for a deck?

Pressure-treated No. 2 for the framing and boards, with fasteners and hangers rated for treated lumber.

What’s the difference between No. 2 and Select Structural?

Both are structural grades; Select Structural is the higher grade, with fewer defects, used where plans call for more strength. Buy what your plans specify.

What length 2x6 stud do I need for a 9-foot wall?

The 104-5/8-inch precut stud frames a 9-foot wall with a bottom plate and a double top plate.

What is appearance-grade lumber?

Boards graded for looks rather than strength: cleaner faces and fewer knots, for interior woodwork you’ll see. Use structural grades for anything that carries a load.