Cedar Lumber

Cedar is a lightweight softwood that resists rot and bugs without a drop of chemical treatment. That’s the whole pitch. Unlike many softwoods, cedar contains natural extractives called thujaplicins that act as powerful fungicides, providing exceptional resistance to rot, decay, and insect damage without requiring chemical treatments. For Montana builders deciding between cedar and treated lumber for a deck, fence, or run of siding, that’s the trade worth understanding before anything else.

But here’s the mistake people make at the counter: they ask for “cedar” like it’s one thing. It isn’t. The species you pick decides whether your project lasts outdoors for decades or just smells nice in a closet. Get that wrong and you’ve wasted money. Get it right and the wood does exactly what you need.

Why Cedar Holds Up Without Treatment

The decay resistance is real, and it comes from the wood itself. Western red cedar is one of the longest lived and most decay- and insect-resistant softwood species in North America. That’s not marketing — it’s why First Nations builders and modern contractors both reach for it.

The other half of cedar’s appeal is stability. Western red cedar wood is light in weight, uniformly textured, straight-grained and contains no resin. All these make the wood easy to work with. It is a preferred species in applications where decay-resistance, dimensional stability and good insulation value are important. That stability matters more here than most places. Cedar experiences minimal expansion and contraction with changes in humidity, making it ideal for outdoor applications where other woods warp and crack. Montana swings from dry interior winters to wet spring thaw, and cedar shrugs that off better than most.

It’s light, too. Dry western red cedar weighs an average of just 23 pounds per cubic foot, making it a lightweight option that’s easy to handle. Easier on the back, easier on the install.

How long does it last? Cedar has a natural resistance to rot and insects. It’s known for its durability and long wear life. Finished and maintained properly, cedar will last 40, 50, 60, even 70 years. Left bare, it doesn’t fail — it just changes color. Its color gradually changes to silver-gray with aging. That graying is cosmetic. The wood underneath keeps doing its job.

Species Matter More Than Anything Else

This is where the buying decision actually lives. The cedars split into two camps: outdoor structural wood and indoor aromatic wood. They are not interchangeable.

Western Red Cedar is the construction standard. Western Red Cedar grows in the Pacific Northwest and represents the most widely used cedar species for construction. The heartwood displays a rich reddish-brown color that darkens with age. With a Janka hardness rating of just 350 lbf, Western Red Cedar is exceptionally soft and lightweight. Best uses include exterior siding, roofing shingles, decking, fencing, and outdoor furniture. Its natural decay resistance lasts for decades without chemical treatment. One key thing that trips people up: it does not have the strong odor associated with its eastern cousin. If you want that closet smell, this isn’t the one.

Eastern Red Cedar — what most folks know as aromatic cedar — is a different animal entirely. This variety is famous for its strong aromatic scent, created by high concentrations of natural oils. These oils repel moths and insects effectively, making Eastern Red Cedar the traditional choice for closet lining and hope chests. The Janka hardness of 900 lbf makes it significantly harder than Western Red Cedar. It also works for fence posts — Aromatic Red Cedar is frequently used for fence posts used in direct ground contact with no pre-treating of the wood. But don’t expect wide, clean boards. It is a very slow-growing species, and most trees harvested tend to be fairly small in diameter. Because of this, Aromatic Red Cedar boards tend to be knotty and narrow.

Alaskan Yellow Cedar steps up for heavy-duty work. Alaska yellow cedar combines the decay resistance of western red cedar with a higher density, making it suitable for heavy-duty applications. Its pale yellow hue and tight grain lend it a distinct aesthetic, perfect for high-end projects like boats, bridges, and musical instruments. It runs harder than Western Red — a Janka rating of 580 lbf.

Inland Red Cedar is the regional sleeper, and it’s worth knowing for Montana jobs. Inland Red cedar is the same species as Western Red cedar; the difference is where it grows. While Western Red cedar grows exclusively in western coastal North America and is referred to as coastal cedar, Inland Red cedar grows further east into the Rocky Mountains. The Rocky Mountain climate changes the wood. The Inland Red cedar trees don’t grow as large as Western Red cedars due to more seasonal changes and a dryer climate. This causes these smaller cedars to branch more, and more branches equal more knots. It’s harder to find Inland cedar in a grade higher than Select Tight Knot. The upside: Inland Red cedar is rot and insect resistant and is a great choice for siding, fencing, decking, and outdoor entertainment spaces. If you’re looking for a rustic, lighter-colored cedar, Inland cedar is an excellent option.

Species	Janka Hardness	Color	Best For
Western Red Cedar	350 lbf	Reddish-brown	Siding, decking, fencing, trim, timbers
Eastern/Aromatic Red Cedar	900 lbf	Purple-red	Closet & chest lining, fence posts
Alaskan Yellow Cedar	580 lbf	Pale yellow	Heavy-duty, high-end work
Inland Red Cedar	Same as WRC	Lighter, less variation	Rustic siding, fencing, decking

The decision path is simple. Outdoor and structural — decking, siding, fencing, trim, beams — reach for Western Red or Inland Red. Storage that needs to repel moths — closets, chests — that’s Eastern/Aromatic Red. Want the premium clear look with no knots, go Western Red. Rustic and lighter-colored, Inland Red earns its keep.

Grades, Sizes, and Profiles — Reading the Stamp

Grade drives both appearance and cost. The split runs clear versus knotty. Bevel siding is available in clear and knotty grades. Clear siding gives premium quality appearance and is ideal for prestigious, upmarket applications. Knotty siding has warmth and casual charm and is ideal for homes, cottages, club-houses and applications where a rustic appearance is desired. You’ll see grade names like Clear V.G. Heart at the top end and Select Knotty for the rustic side.

For siding, bevel is the workhorse. Western Red Cedar bevel siding is the most widely used cedar siding type. It is produced by resawing lumber at an angle to produce two pieces thicker on one edge than the other. Also known as clapboard and lap siding, it is thick on the bottom edge, roughly ¾” to 1”, and tapers to about an ⅛” to ¼” at the top. There are alternatives. Channel rustic is lap siding with a 2” indentation at the top of the board called the channel — a shiplap product rather than T&G. Rabbeted Bevel siding is an upgrade to a standard bevel with a shiplap bottom that gives the finished siding a more pronounced profile. If you need long runs with fewer joints, finger-joined bevel siding is available in lengths up to 16 feet and provides the handsome appearance and all-weather performance of premium cedar siding. Builders appreciate both the convenient long length tally and the speed and ease of installation with fewer field joints.

For interior paneling, look to pattern lumber. When the term describes a single board, it often refers to tongue and groove panels. Cedar T&G boards are available in a v-joint pattern, as well as a v-joint with a bead. These boards are most often used as interior wall paneling instead of drywall and also as wainscotting.

For structural and exposed-beam work, timbers cover the range. Timbers are finished structural lumber larger than standard 2x dimensions, formed into beams or planks. They are available in thicknesses from 4” through 12” and in various widths and lengths. Depending on their end-use, they can be found as both rough-sawn timber or surfaced on all four sides (S4S).

Boards round out the list, and they show up everywhere. WRC is sold in different grades, with “appearance” or “appearance knotty” being the most popular. Among the cedar board dimensions stocked are 1x4, 1x6, and 1x8 profiles surfaced one side, two edges, in lengths running from 8 up to 14 feet — the kind of stock that handles trim, fascia, shelving, and finish work.

Now the part that matters most before anything touches a wall in Montana’s dry interior: moisture content. Verify that boards are kiln-dried or air-dried to under 19% moisture to prevent warping. Always check end stamps for species and moisture content. Boards that come in wet will keep moving after they’re installed. Check the stamp.

Working With Cedar — Handling Cautions

Cedar’s softness cuts both ways. The wood is easy to work with hand tools and machines, but it dents more easily than hardwoods. Because it’s soft, it splits. Use professional-grade fasteners and pre-drill pilot holes, as cedar is soft and prone to splitting. On anything exterior, leave expansion gaps to accommodate natural movement.

And protect your lungs. Wear a respirator, as cedar dust can cause respiratory or skin irritation. That goes double for Eastern Red — it reportedly has a high silica content, which can dull cutters, and in many applications the wood is left unfinished to preserve its aromatic properties.

Frequently Asked Questions

Is cedar better than treated lumber for a deck? For outdoor durability without chemicals, cedar earns its place. Western Red Cedar overcomes the negative aspects of most wood products due to its weather-resistant qualities and naturally occurring preservatives that resist insects and decay. It’s also light and takes finishes well. The trade-off is softness — it dents more readily than a hardwood, so pre-drilling and good fasteners matter.

Which cedar should I use for a closet or storage chest? Eastern/Aromatic Red Cedar. It is famous for its strong aromatic scent, created by high concentrations of natural oils. These oils repel moths and insects effectively, making Eastern Red Cedar the traditional choice for closet lining and hope chests. Western Red won’t give you that — it lacks the strong scent.

What’s the difference between clear and knotty cedar? Appearance and cost. Clear grades are knot-free for premium, visible finishes. Knotty siding has warmth and casual charm and is ideal for homes, cottages, club-houses and applications where a rustic appearance is desired. Knotty reads rustic; clear reads upscale.

Will cedar last if I leave it unfinished? Yes — it just changes color. Bare cedar gradually changes to silver-gray with aging. That patina is cosmetic only; the decay resistance comes from the wood, not the finish. Finished and maintained, cedar can run decades.

Is Inland Red Cedar as good as Western Red Cedar? Same species, grown in the Rockies instead of the coast. It’s harder to find Inland cedar in a grade higher than Select Tight Knot. Inland Red cedar is non-resinous, dimensionally stable and very durable in all climates and weather conditions. Expect more knots and a lighter, more uniform color.

Why do I need to check the moisture content stamp? Because wet boards keep moving. In Montana’s dry interior, lumber that goes in above 19% moisture will shrink and shift after install. Verify that boards are kiln-dried or air-dried to under 19% moisture to prevent warping.