Cedar has been a valued building material for centuries, prized for its natural resistance to decay, dimensional stability, and distinctive aromatic properties. From ancient Mediterranean civilizations that used cedar for shipbuilding and temple construction to modern builders who specify cedar for decking, siding, and structural elements, this wood family continues to perform across a wide range of applications. Cedar trees, coniferous evergreens reaching 50 to 100 feet at maturity, produce wood with a straight grain, relatively low density, and a natural oil content that repels moisture and insects. Understanding the differences between cedar species, their physical properties, and how to select the right grade for a given project determines whether a cedar installation lasts twenty years or sixty.
Characteristics That Make Cedar a Preferred Building Material
Cedar stands apart from other softwoods and hardwoods because of several innate properties that reduce maintenance requirements and extend service life. Builders who understand these characteristics can make informed decisions about where to use cedar versus treated lumber, composite materials, or other wood species.
Natural Durability Factors
The heartwood of most cedar species contains natural preservatives called thujaplicins and phenolic compounds. These chemicals inhibit fungal growth, deter termites and carpenter ants, and reduce the rate of moisture absorption. Unlike pressure-treated lumber that relies on chemical infusion after milling, cedar’s protection is integral to the wood structure and does not leach out over time. The American Wood Protection Association classifies western red cedar as having moderate to high natural durability, with expected ground-contact service lives of 15 to 25 years and above-ground service lives exceeding 40 years in most climates.
Moisture Resistance
Cedar’s cellular structure includes extractives that reduce capillary action, meaning the wood resists wicking water into its fiber matrix. When properly detailed with flashing and ventilation gaps, cedar siding and decking exhibit shrinkage and expansion rates approximately half that of pine and fir species. This dimensional stability reduces crack development at fastener points and minimizes the gap formation between boards during dry seasons.
Major Cedar Species Used in Construction
Not all cedar performs the same way. Builders and specifiers need to distinguish between the true cedars of the Cedrus genus, the arborvitae species commonly marketed as cedar, and the incense and Port Orford cedars that fill specific niche roles. The table below summarizes the key species and their primary construction uses.
| Species | Scientific Name | Janka Hardness | Primary Uses | Natural Durability |
|---|---|---|---|---|
| Western Red Cedar | Thuja plicata | 350 lbf | Siding, decking, fencing, outdoor furniture | High |
| Eastern Red Cedar | Juniperus virginiana | 900 lbf | Chests, closet linings, fence posts, carvings | Very High |
| Incense Cedar | Calocedrus decurrens | 470 lbf | Pencils, window frames, interior millwork | Moderate |
| Northern White Cedar | Thuja occidentalis | 320 lbf | Log homes, fencing, greenhouse framing | Moderate |
| Port Orford Cedar | Chamaecyparis lawsoniana | 720 lbf | Boatbuilding, flooring, structural beams | Very High |
Western red cedar dominates North American construction markets because it combines good durability with wide availability and workability. Eastern red cedar, technically a juniper, offers superior decay resistance and a distinctive reddish heartwood but is typically available only in smaller dimensions. Northern white cedar is the lightest and softest of the group, making it suitable for log home construction where ease of cutting and handling offsets its lower structural capacity.
Deodar Cedar and Other Global Species
The Himalayan cedar, or deodar (Cedrus deodara), is a true cedar native to the western Himalayas that produces timber with a warm golden-brown color and a pronounced fragrant oil. Deodar has long been used in Indian and Pakistani construction for structural framing, door panels, and railway sleepers because its heartwood resists termite attack even in tropical conditions. Its growth rate and mature height, often exceeding 100 feet, produce long clear-grain sections suitable for columns and beams without finger-jointing. The tree requires full sun and well-drained sandy soil to reach commercial size, which limits plantation development outside its native range. Cedar species from the Mediterranean basin, including Cedrus atlantica and Cedrus libani, produce wood with similar properties but lower commercial volumes due to protected status in their native habitats.
Using Cedar for Exterior Decking and Siding
Exterior applications account for the largest share of cedar consumption in residential and light commercial construction. When comparing cedar decking to pressure-treated wood and composite alternatives, several factors influence the decision. Cedar deck boards weigh less than composite, making them easier to handle during installation. They can be sanded and refinished when surface wear occurs, whereas composite boards with damaged surface layers typically require full replacement. Cedar also remains cooler under direct sunlight than dark composite materials, a consideration for barefoot deck use in hot climates.
Installation Best Practices for Cedar Decking
- Use stainless steel or hot-dipped galvanized fasteners. Standard electroplated nails react with cedar’s natural extractives and produce black staining around each fastener within months.
- Pre-drill fastener holes within 1 inch of board ends to prevent splitting. Cedar’s relatively low density makes it prone to split when fasteners are driven without pilot holes in end-grain areas.
- Maintain a 1/8-inch gap between deck boards for drainage and airflow. Cedar shrinks slightly as it dries, so gaps installed during wet weather may widen during dry periods.
- Apply a water-repellent finish within two weeks of installation to slow UV graying. Untreated cedar exposed to sunlight turns silver-gray within three to six months, a cosmetic change that does not affect structural performance.
Cedar siding installation follows similar principles but requires additional attention to flashing details at corners, windows, and doors. Horizontal lap siding should overlap by at least 1 inch, and butt joints should occur over studs or solid blocking. A ventilated rainscreen gap between the siding and the building wrap extends paint life by allowing the back side of the boards to dry between rain events.
Interior Applications and Flooring with Cedar
Inside the home, cedar serves both functional and aesthetic roles. The aromatic oils that make cedar resistant to decay also repel clothes moths and carpet beetles, which is why eastern red cedar has been the traditional material for hope chests and closet linings since the nineteenth century. Western red cedar is commonly specified for saunas and steam rooms because the wood does not develop surface temperatures high enough to burn skin and resists the moisture cycling that causes other species to cup and crack.
Interior wall paneling and ceiling treatments benefit from cedar’s straight grain and knot patterns. Clear-grade material, selected for minimal knots and uniform color, produces a refined appearance suitable for living rooms and studies. Knotty-grade cedar, with visible tight knots and color variation, fits rustic or cabin-style interiors. For existing installations that have darkened over time from UV exposure and oxidation, specific restoration techniques using oxalic acid bleaching can return the wood to its original tone without sanding away the surface character.
While oak, maple, and hickory dominate the flooring market, cedar flooring offers advantages in specific settings. Port Orford cedar, with a Janka hardness rating of 720 lbf, stands up to moderate foot traffic while providing a uniform pale color that accepts stains evenly. The material works well in bedrooms, studies, and climate-controlled vacation homes where the aromatic presence adds to the atmosphere. When selecting a wood flooring system for a cedar-floored room, property owners should match the expansion characteristics of the flooring material to the subfloor construction. Cedar’s lower dimensional movement compared to red oak means fewer seasonal gaps and less risk of buckling in humid climates.
Working with Cedar: Cutting, Fastening, and Finishing
Cedar is among the most workable construction woods, which is one reason it has remained popular despite competition from synthetic materials. The wood cuts cleanly with standard woodworking tools, sands to a smooth surface with 120-grit or higher abrasives, and accepts a wide range of finishes. Builders should take several precautions to get optimal results.
Cutting and Machining Guidelines
- Use carbide-tipped blades and bits for production work. Cedar’s silica content, while lower than in tropical hardwoods, dulls high-speed steel tooling noticeably faster than pine or fir.
- Set saw blade height to extend no more than 1/4 inch above the workpiece to minimize tear-out on the bottom face of cedar boards.
- Feed stock through planers and jointers at moderate speeds. Forcing cedar through at high feed rates produces a chipped, fuzzy surface that requires additional sanding.
- Vacuum dust during machining. Cedar dust contains aromatic compounds that can cause respiratory irritation in enclosed spaces, and fine particles accumulate static charge on shop surfaces.
For exterior projects, applying a penetrating oil finish or a semi-transparent stain produces more durable results than film-forming paints and varnishes, which tend to peel from cedar surfaces as the wood cycles moisture. When painting cedar is desired, an oil-based primer applied to all six sides of each board before installation prevents extractive bleed-through that can stain latex topcoats. On existing cedar decks that require surface updates, installing ceramic tile over the wood substrate provides a durable low-maintenance surface option, provided the framing is reinforced to handle the additional dead load of tile and mortar.
Cedar Grading, Sizing, and Procurement
The Western Red Cedar Lumber Association and the Northern Softwood Lumber Bureau publish grading rules that define cedar quality levels for construction buyers. Clear Heart grade contains no knots and is limited to heartwood, producing the highest stability and appearance. Select Knotty allows sound tight knots up to a specified size, which is the most common grade for decking and siding. Utility grade includes larger knots and some wane, suitable for fencing and agricultural structures where appearance is secondary. Buyers should verify that cedar lumber is surfaced on four sides when used for visible applications, as S4S material ensures consistent thickness and eliminates the rough saw marks that trap moisture on S2S or rough stock.
Standard cedar decking is available in 5/4 by 6-inch nominal dimensions, yielding a 1-inch-thick board after surfacing. Tongue-and-groove cedar V-joint paneling comes in 1×6, 1×8, and 1×10 patterns for interior wall and ceiling applications. For exterior cladding, beveled cedar siding in 1/2-inch by 6-inch or 3/4-inch by 8-inch profiles provides the classic horizontal lap appearance with the natural weather resistance that has made cedar a standard for North American residential exteriors since the colonial period. Pricing for cedar fluctuates with housing starts and mill capacity, typically running 1.5 to 3 times the cost of pressure-treated pine for equivalent dimensions, offset by a service life two to three times longer in above-ground applications.