Cedar 2x10 Lumber

A cedar 2x10 is a dimensional board milled from Western Red Cedar — the same wood deck builders and timber-frame crews reach for when a board needs to fight off moisture without chemical treatment. Western Red Cedar is naturally resistant to rotting, decay and insect infestations, which is exactly why it earns its keep on the parts of a project you can actually see: deck framing, beams, fascia, pergolas, and exposed cabin-style interiors.

Here’s the honest framing. Cedar costs more than SPF or pressure-treated. So you reserve it for visible and moisture-exposed roles where its looks and decay resistance pay off — not for hidden framing buried inside a wall where nobody will ever see it. For visible, architectural-grade uses, Western Red Cedar 2x10s are chosen for their aesthetic appeal, natural decay resistance, and workability and straight grain — often found in pergolas, fascia, eaves, and porch ceilings, where beauty and function must align.

Western Building Center carries cedar 2x10s in 10-foot and 12-foot lengths, surfaced one side, two edges (S1S2E).

Dimensions: Nominal Versus Actual

This trips up buyers every time. A “2x10” is not actually 2 inches by 10 inches. A 2×10 board actually measures 1.5 inches thick by 9.25 inches wide. This reduction is the result of the planing process after the board is cut rough to nominal size. That’s the standard for a surfaced (S4S) board, and a 2”x10”x10’ Western Red Cedar measures 1 1/2” x 9 1/4” x 120”, great for deck joists, beams and fascia, as well as appearance grade applications.

Rough-sawn cedar is a different animal. It stays closer to full size because it hasn’t been planed down. Listed actual dimensions for rough-sawn 2x10 run a touch under full — rough sawn red cedar with actual dimensions of 1-3/4” x 9-3/4”, and a green rough board runs approximately 1-11/16 in thick by 9-3/4 in wide.

That dimensional difference matters for layout. Plan your spacing and fastening around the actual size, not the nominal label, or your fascia reveal and joist tops won’t line up.

Surface / Type	Actual Thickness	Actual Width
Surfaced (S4S)	1.5 in	9.25 in
Rough-sawn	1-3/4 in	9-3/4 in
Rough-sawn (green, alt. spec)	1-11/16 in	9-3/4 in

Lengths run the standard ladder. 2x4, 2x6, 2x8, 2x10, and 2x12 are available in lengths up to 20 feet, with offerings spanning 8, 10, 12, 14, 16, 18, and 20 feet depending on the mill.

Grade, Surface Finish, and Moisture — The Three Decisions

Picking a cedar 2x10 comes down to three choices, and each one shifts appearance, stability, and what you’ll pay.

Grade. WRC is sold in different grades, with “appearance” or “appearance knotty” being the most popular. For flawless finish work, clear grade is the call. For visible work where some character is fine, Select or Select Knotty (STK) Appearance Grade holds up. For framing, #1 or #2 Common does the job. Know what #2 actually allows: No. 2 grade lumber is used in all general construction; this grade is designed for the many uses where higher strength properties are not needed and where serviceability is important — few defects are permitted and knots of any quality are allowed as long as they are well spaced and do not exceed size regulations.

Surface. Smooth or rough — it’s an appearance decision first. Rough sawn cedar is chosen mainly for its raised grain and rustic appearance. Tannish brown in color, the grain pattern is tight with few knots. S4S gives you a smooth, finished face. The WBC cedar 2x10 is surfaced one side and two edges (S1S2E) — a middle ground that smooths the show face and edges while leaving the back closer to rough.

Moisture. This is where Montana’s seasonal swings come into play. Kiln-dried is the more stable choice. The kiln-drying process reduces moisture content to below 19%, helping minimize warping, twisting, and shrinkage after installation. Green cedar — surfaced green, moisture content in excess of 19% — runs cheaper but moves as it dries. Where seasonal moisture cycling drives shrinkage and movement, kiln-dried earns the upgrade.

One more reason cedar finishes well: Western red cedar is pitch and resin-free, which means it’s ideal for accepting and holding a wide range of beautiful finishes including elegant dark stains, shabby chic bleaches, traditional solid colors and naturally beautiful semi-transparents.

Spans, Structural Use, and Fasteners

When a cedar 2x10 carries load — deck joists, rafters, a built-up beam — respect the span tables. Cedar span data covers No.2 grade Western Cedar lumber ranging from 2x6 to 8x12 dimensions, with maximum span calculations from 6 to 20 feet and corresponding load capacities measured in pounds per lineal foot.

Worth noting for snow country: rafter span tables built for snow load conditions (30 lbs per square foot snow load plus 10 lbs per square foot dead load) carry deflection limits of L/240, covering spacing options from 12 inches to 24 inches on center. Montana’s state minimum ground snow load is 30 psf, but local values climb with elevation — run your site through the MSU snow load tool at snowload.montana.edu and let local code govern the final call.

Two practical levers on capacity. Double member configurations effectively double load capacity compared to single members. And spacing costs you span: larger spacing intervals (24” OC) reduce effective rafter spans by approximately 20-25% compared to 12” OC spacing.

On fasteners and install:

• Use corrosion-resistant hardware. For structural connections, common fastening methods include 16d common nails, 3.5”–4” deck screws, structural screws, joist hangers and hurricane ties. When using treated lumber, only hot-dip galvanized, zinc-coated, or stainless steel fasteners should be used to resist corrosion.
• Drill pilot holes near board ends to keep cedar from splitting.
• Let it settle in before you fasten it down. For proper installation of decking, allow lumber to acclimate on site 1-2 weeks prior to installation.
• Always confirm spans against local code — maximum spans vary by load and grade.

Frequently Asked Questions

What is the actual size of a cedar 2x10? A surfaced (S4S) cedar 2x10 measures 1.5 inches thick by 9.25 inches wide — the nominal “2x10” is the rough-cut size before planing. Rough sawn cedar stays closer to full, with actual dimensions of 1-3/4” x 9-3/4”. Layout off the actual dimension, not the label.

Where does cedar 2x10 make the most sense? Visible and moisture-exposed roles. Deck joists, beams and fascia, as well as appearance grade applications — plus pergolas, eaves, porch ceilings, and exposed cabin-style interior framing. Cedar framing lumber can be left exposed as an interior finish option — a common practice in cabin home construction. Cedar’s strength means it can be used in structural situations, and its natural ability to resist insect infestation is an added benefit.

Should I buy kiln-dried or green cedar? Kiln-dried (under 19% moisture content) is the more dimensionally stable choice and resists warping and shrinkage after install. Green cedar carries moisture content in excess of 19% — cheaper, but it’ll move as it dries. Where seasonal moisture swings are the rule, kiln-dried is worth it.

Does cedar need pressure treatment for outdoor use? No — that’s cedar’s whole appeal. Cedar’s natural oils and preservatives fight off weather, bugs, fungi and algae and, if desired, allow excellent absorption of stains and paint. It earns its place outdoors on its own merits, which is why it’s reserved for exposed work rather than hidden framing where treated or SPF is more economical.

What grade should I specify? Clear for finish work, Select or STK Appearance Grade for visible work, and #1 or #2 Common for framing. No. 2 grade is designed for uses where higher strength properties are not needed — knots of any quality are allowed as long as they are well spaced and do not exceed size regulations. Match the grade to how much the board will be seen and how hard it has to work.