Choosing an exterior material means weighing first cost against decades of maintenance, appearance, and environmental impact. Western red cedar keeps winning that comparison for homeowners who want a natural product that ages gracefully. Cedar siding offers the widest range of textures, profiles, and finishing options of any cladding material, and it can be installed horizontally, vertically, or in shingle patterns. The species grows along the Pacific coast of North America, where its natural extractives resist decay and insects, which is why it has been used for everything from coastal homes to storage buildings for generations. The western red cedar for residential exteriors reference covers the material properties, installation methods, and finishing practice in detail. Cedar is also one of the few siding materials that stores carbon for the life of the building, a point that matters more to buyers every year.
Properties That Make Cedar a Workhorse
Western red cedar earns its place in the material lineup through a specific set of physical properties. It is among the lightest commercial softwoods, which makes it easy to handle and install, yet its cellular structure gives it useful insulating value. The natural extractives called thujaplicins are fungicidal, which is the reason cedar resists decay where it stays wet, and the wood’s low shrinkage makes it dimensionally stable across seasons. Those same properties carry into log home construction, where whole-log walls rely on stability and decay resistance to stay tight for decades.
Physical properties at a glance
| Property | Typical value | Why it matters |
|---|---|---|
| Density at 12 percent moisture | about 370 to 400 kg per cubic metre | light to handle, low dead load |
| Thermal resistance | about R-1.4 per 25 mm | insulates better than most siding |
| Dimensional stability | low shrinkage and swelling | stays flat, fewer gaps |
| Natural durability | moderate to high decay resistance | performs in wet climates |
| Appearance | reddish brown, greys with age | can be left unfinished |
How cedar compares with other claddings
Vinyl costs less up front but expands and contracts with temperature and is difficult to repair. Fiber cement resists fire and insects but is heavy, hard to cut, and energy-intensive to produce. Composites avoid some maintenance but hide their repairs poorly and cannot be recycled like solid wood. Cedar matches most of their strengths while adding repairability, renewability, and a texture range that none of them offer. Contractors also report cedar jobs go faster than fiber cement because the boards cut cleanly and fasten without predrilling.
- Repairability: a damaged board is replaced in place.
- Renewability: certified cedar comes from regrowing forests.
- Versatility: horizontal, vertical, shingle, or board and batten.
- Natural finish: greys gracefully without paint.
Sustainability and the Carbon Story
The environmental case for cedar starts with carbon. Growing trees absorb CO2, and the carbon stays locked in the wood for as long as the building stands; a cubic metre of softwood stores roughly 0.9 tonnes of CO2 equivalent. That makes wood siding one of the few building products that improves the atmosphere instead of adding to it, provided the wood comes from responsibly managed forests. The audience for that message keeps growing: surveys of younger buyers show climate change is the leading concern of the generation now entering the housing market, and they say they will pay more for sustainable products. Next-gen builders embrace western red cedar precisely because it delivers the sustainability story without asking them to compromise on appearance or performance.
How wood stores carbon
The carbon math runs in the wood’s favour from the first year. A growing cedar stand pulls CO2 out of the air faster than mature trees release it, and only a fraction of the harvested volume is lost in milling. Concrete production, by comparison, emits roughly 300 kg of CO2 per cubic metre, and steel far more. Over a 60-year building life, the wood cladding keeps its carbon locked up while the manufactured alternatives carry their production emissions on the books from day one.
Sourcing and certification
Responsible sourcing is what keeps the carbon story honest. Look for third-party certification that tracks the wood from certified forest to final product, and ask suppliers where the logs came from. Regional sourcing shortens transport and supports local mills, and it gives the buyer a direct line to the grower when questions about species or grade come up.
Substrate Matters at Every Scale
The word substrate appears at every scale of construction, from the ground under a building to the surface under a finish. At the site scale, the substrate is the ground itself, and its geology decides what can be built and how. Ancient builders understood this instinctively; the builders of the Acropolis chose a site whose geotechnical features of the bedrock provided a stable base for stone structures that still stand after 2,400 years. At the wall scale, the substrate is the sheathing and air barrier under the siding, and its flatness, dryness, and attachment decide whether the cladding lasts.
Substrate at the wall scale
Wall substrate starts with the structural sheathing, usually plywood or oriented strand board, covered by a weather-resistive barrier that sheds liquid water while letting vapour pass. Furring strips create a drainage gap behind the cladding, and the fasteners that anchor the siding must reach solid structure, not just the sheathing face. Each layer has one job, and the substrate is the layer that carries everything else.
Why substrate fails first
When an exterior fails, the substrate is usually the first casualty. Water that gets behind the siding soaks the sheathing, rusts the fasteners, and rots the framing before the finish shows any sign of trouble. By the time the siding looks wrong, the repair has already grown into a structural job. Checking the substrate during construction costs minutes; replacing it after the fact costs weeks.
Inspect the Substrate Before You Finish
Sealants, adhesives, and finishes only perform as well as the surface they are applied to. Substrate inspection for sealant and adhesive applications is a defined procedure: check that the surface is clean, dry, and sound, verify the temperature window, and confirm the material is compatible with the substrate before the first bead goes down. Skipping the inspection is the most common cause of premature failure in exterior work, and the fix costs far more than the check.
Inspection checklist
- Confirm the substrate is dry with a moisture meter.
- Remove dust, oil, and loose material from the bond area.
- Check flatness and fill gaps wider than 6 mm before finishing.
- Verify air and surface temperatures against the product data sheet.
- Prime porous surfaces where the manufacturer requires it.
- Test adhesion on a small patch before full application.
Moisture thresholds for common substrates
| Substrate | Acceptable moisture | Test method |
|---|---|---|
| Wood | below 15 percent moisture content | pin-type meter |
| Plywood and OSB | below 12 percent moisture content | pin-type meter |
| Concrete | below 75 percent relative humidity | RH probe |
| Gypsum board | below 1 percent moisture content | pin-type meter |
The numbers matter because sealants and adhesives fail silently: the bond looks fine for months, then lets go in the first temperature swing. A 20-minute inspection on a dry day protects a job that is expected to last decades.
Building Science and the Complete Wall Assembly
Cedar siding performs best when the whole wall is designed as a system. Building science principles for builders and homeowners start with controlling water, air, and vapour layers, and cedar’s natural permeability works with that design: it lets moisture escape while shedding rain. A ventilated rain screen gap behind the siding is the single best upgrade for any cladding, because it lets the back of the boards dry and equalizes pressure so wind-driven rain cannot be pushed through the joints. Understanding why building science matters turns a material choice into a durable assembly.
Rain screen basics
A rain screen is simply a gap. Furring strips or a drainage mat create a 10 to 20 mm space between the weather-resistive barrier and the back of the siding, with weep openings at the bottom and vents at the top. Air moves through the gap, drying the wall, and any water that penetrates the cladding runs down the barrier and out through the weeps instead of pooling against the sheathing.
Fastening and spacing rules
Cedar moves with humidity, so the installation rules give it room. Lap siding should overlap 19 to 25 mm, joints should sit on solid backing with a small gap for movement, and fasteners should be stainless steel or hot-dipped galvanized, driven so they hold without crushing the wood. Nail at the top edge of each course so the next board covers the fasteners.
Craftsmanship Decides the Outcome
The best material in the catalogue will fail under careless installation, and a modest material installed with care will outperform it. Why craftsmanship matters in building quality shows up in every long-lived cedar building: consistent reveals, properly set fasteners, and flashing details that shed water before it reaches the wood. Cedar rewards the installer who cuts clean, primes end grain, and leaves the material room to move with the seasons. In return, a well-installed cedar exterior can go 30 years or more between refinishing cycles, which is the payoff every homeowner is actually buying. The difference between a 15-year siding job and a 40-year siding job is rarely the species of wood; it is the quality of the air barrier, the flashing, and the joints. Contractors who photograph their details and walk the wall after installation catch the mistakes before the owner does, and that habit alone raises the average life of the exterior by a decade.