Cedar 2x6 Lumber

Cedar 2x6 is a naturally durable softwood that handles exterior exposure without chemical treatment. The two decisions that matter most are grade and surface. Get those right, match them to whether the board will be seen or do structural work, and you’ve made the call that separates a deck that ages gracefully from one that doesn’t.

Here’s the short version. Western Red Cedar is a popular choice for outdoor and indoor applications because of its durability, attractive appearance, and ease of workability — and because it’s naturally resistant to decay and insect damage, it’s a good choice for decking, siding, and fencing. Cedar’s natural oils and preservatives fight off weather, bugs, fungi and algae, and they also allow excellent absorption of stains and paint. No pressure treatment, no ACQ, no ground-contact rating to chase. The wood does it on its own.

A nominal 2x6 isn’t actually two by six. Actual dimensions run 1-1/2 inches by 5-1/2 inches. Western Building Center stocks cedar 2x6 in 8, 10, 12, and 16-foot lengths. That covers most deck framing, fence rail, pergola, and trim runs without a lot of waste.

What Cedar 2x6 Is and Why It Resists Rot

The rot resistance is the whole reason cedar costs more than standard framing stock. It’s built into the wood. As one of North America’s most durable woods, cedar has a natural resistance to deterioration, and its large, open cell structure makes it less dense than most other softwoods — which makes it easy to move around on the job. It’s uniformly textured, straight-grained, and contains no resin.

That resin-free trait does double duty. Western Red Cedar is pitch and resin-free, which means it readily accepts and holds a wide range of finishes including dark stains, bleaches, solid colors, and semi-transparents. Whatever look the job calls for, the wood takes it.

Workability is the other reason crews like it. It’s lightweight and easy to nail, saw, trim, or cut. For Montana exterior work, the dimensional behavior matters as much as anything. Cedar’s superior dimensional stability means that, when properly installed and maintained, components are likely to stay straight and flat, and resist warping and cupping season after season. That comes down to its low wood density and low shrinkage factor. Through wet springs and dry late summers, that stability keeps decking flat and siding tight.

Grades and Surfaces: Clear vs. STK, S4S vs. Rough Sawn

Two questions decide which board you buy. Will it be seen? And does it carry load?

Grade handles the appearance question. Clear A&Better grade is kiln-dried, knot-free cedar — the premium look. When it’s S4S, both sides and edges are planed smooth, with an actual board dimension of 1-1/2 inches thick by 5-1/2 inches wide. Step down to Select Tight Knot (STK), also called appearance grade, and you get a rustic look with sound knots — still naturally resistant to rot, decay, and insect attacks. Clear costs more and reads refined. STK costs less and reads rustic. Neither one gives up the decay resistance.

Surface is the second choice. S4S means surfaced on four sides — planed smooth, ready to finish. Rough sawn, also known as rough cut, is untreated and cut into planks, generally sturdier-looking than smooth-surfaced lumber. Western Building Center’s cedar 2x6 is run S1S2E — surfaced one side, two edges — which gives you a finished face and clean edges while keeping one side in a more natural state.

Before you commit, read the stamp. Look for S-DRY or KD19 markings to confirm the lumber is kiln-dried for stability. Green cedar moves more after install; kiln-dried holds its shape.

Spec	Detail
Nominal size	2x6
Actual dimensions	1-1/2” × 5-1/2”
Species	Western Red Cedar
Stock lengths (WBC)	8’, 10’, 12’, 16’
Surface (WBC)	S1S2E
Premium grade	Clear / A&Better — knot-free
Appearance grade	Select Tight Knot (STK) — sound knots
Kiln-dried stamp	S-DRY or KD19

Applications and Structural Limits

Cedar 2x6 covers cosmetic and structural ground, which is exactly why grade matters. It’s a top choice for outdoor projects like siding, decking, and ceilings. It’s also suitable for cedar posts, framing, decks, planter boxes, furniture, and many other projects. Visible work — siding, deck boards, pergola slats, trim — wants appearance grade. Structural work wants graded structural lumber.

When the board carries load, the numbers come from a graded structural product. No.2 grade Western Cedar is covered by load tables for beam, header, and rafter applications, and the species group — including Western Red Cedar — meets WWPA Western Lumber Grading Rules 2021 standards for structural use.

Cedar is softer than fir or pine, so it carries less. The numbers bear that out. A 2x6 supports 127 lbs per lineal foot at a 6-foot span. Double-member configurations effectively double load capacity compared to single members. As for reach, 2x6 members are effective up to about 14 feet depending on size and spacing.

The snow load detail is where Montana builders need to pay attention. The cedar rafter span tables are built for snow load conditions — 30 lbs per square foot snow load plus 10 lbs per square foot dead load — with deflection limited to L/240, covering spacing from 12 to 24 inches on center. That 30 psf figure is the state minimum. Across most of western Montana, site-specific snow loads run higher with elevation. Pull the actual value from the MSU snow load tool at snowload.montana.edu and verify any structural cedar against local code. Don’t assume the table number covers your roof.

Installation Basics

Cedar’s natural oils — the same ones that fight rot — react badly with the wrong fasteners. Use corrosion-resistant fasteners like stainless steel to prevent chemical reactions with cedar oils. Galvanized that’s not rated for cedar will bleed black streaks down a fresh deck. Stainless avoids the staining entirely.

Cedar splits if you force it. Pre-drill pilot holes to avoid splitting, since cedar is prone to it. Five minutes with a drill saves a cracked board at the end of a run.

Let the wood settle before you fasten anything. For proper installation of decking, allow lumber to acclimate on site 1 to 2 weeks prior to installation. In Montana’s dry air, moisture content shifts after delivery — boards that go down tight off the truck can gap or cup once they reach equilibrium. Acclimation is more than a formality here.

And buy extra. A 15% buffer accounts for waste, and with cedar’s varying lengths, ordering 10 to 15% over keeps you from a second trip mid-project.

Frequently Asked Questions

What are the actual dimensions of a cedar 2x6? A nominal 2x6 measures 1-1/2 inches by 5-1/2 inches. Western Building Center carries it in 8, 10, 12, and 16-foot lengths.

Does cedar need to be pressure treated for outdoor use? No. Western Red Cedar is naturally resistant to rot, decay, and insects thanks to its natural oils and preservatives, which fight off weather, bugs, fungi, and algae. That’s what makes it suitable for exposed exterior work without chemical treatment.

What’s the difference between Clear and STK cedar? Clear (A&Better) grade is knot-free for a premium, refined look. Select Tight Knot (STK), or appearance grade, has sound, encased knots for a rustic look. Both keep cedar’s full decay resistance — the difference is appearance and cost.

What does S4S mean versus rough sawn? S4S means surfaced on four sides — planed smooth on both faces and edges, ready to finish. Rough sawn, or rough cut, is left untreated and textured. Western Building Center’s cedar 2x6 is run S1S2E, surfaced one side and two edges.

How much load can a cedar 2x6 carry? A single No.2 cedar 2x6 supports 127 lbs per lineal foot at a 6-foot span, and it’s effective up to about 14 feet depending on spacing and load. Doubling the member roughly doubles capacity. Cedar is softer than fir or pine, so always verify structural use against local code.

Why do span tables matter for Montana builds? Cedar rafter span tables are built around a 30 psf snow load plus a 10 psf dead load with L/240 deflection. That 30 psf is the state minimum — most of western Montana runs higher with elevation. Check the MSU snow load tool at snowload.montana.edu for your site-specific value.

What fasteners should be used with cedar? Corrosion-resistant fasteners such as stainless steel. Cedar’s natural oils react with non-resistant metals and cause staining, so stainless protects the finish.

Should cedar be acclimated before installation? Yes. Let the lumber acclimate on site for 1 to 2 weeks before installation. In Montana’s dry climate, moisture content can shift after delivery, so settling time helps prevent gapping and cupping.