Materials
The board you walk on is only one factor in a deck's lifespan, but it is the one homeowners notice first and maintain most often. In a climate that swings from saturated spring thaws to dry summer heat and back into freezing nights, the decking surface absorbs the most direct weather exposure. This guide compares the three materials used most often on Canadian residential decks: pressure-treated softwood, western red cedar, and wood-plastic composite.
The three common options
Each material trades cost against maintenance and longevity in a different way. None is universally correct; the right pick depends on budget, how much upkeep you are willing to do, and how the deck is exposed to sun and standing moisture.
Pressure-treated softwood
Pressure-treated (PT) spruce, pine, or fir is the default budget surface across much of Canada. The wood is treated with preservatives that resist rot and insects, which is why it is also the standard for structural framing. Freshly treated boards often carry significant moisture and tend to shrink, cup, or check as they dry, so leaving them to acclimatize before fastening reduces movement later.
Western red cedar
Cedar contains natural oils and tannins that give it inherent decay resistance without chemical treatment. It is dimensionally stable, lighter than PT lumber, and stays cooler underfoot in direct sun. Left unfinished it weathers to a silver-grey; to keep its colour it needs a penetrating finish on a regular cycle.
Wood-plastic composite
Composite boards combine wood fibre with recycled plastic. They do not rot, do not need staining, and resist splintering, which is why they have become common on decks where low maintenance is the priority. The trade-offs are a higher upfront cost and greater thermal movement, so composite boards require manufacturer-specified gapping to expand and contract through temperature swings.
Local note: Composite and PT boards both expand and contract with temperature, but they do so on different schedules. Always follow the specific gapping and fastening instructions printed in the manufacturer's installation documentation rather than a generic rule of thumb.
Side-by-side comparison
| Factor | Pressure-treated | Cedar | Composite |
|---|---|---|---|
| Upfront cost | Lowest | Moderate | Highest |
| Maintenance | Periodic cleaning and sealing | Regular finish to retain colour | Cleaning only |
| Decay resistance | Chemically treated | Naturally resistant | Will not rot |
| Thermal movement | Moderate | Low | Higher; needs gapping |
| Surface heat in sun | Moderate | Cooler | Can get warm |
How freeze-thaw changes the calculation
Water is the common thread behind most decking failures. When moisture penetrates wood and then freezes, it expands within the fibres, and repeated cycles open checks and loosen fasteners over time. This is why end grain, the cut ends of boards, is the most vulnerable surface on any wood deck: it absorbs water far faster than the face.
- Seal the cut ends of PT and cedar boards before or during installation.
- Leave consistent gaps between boards so meltwater drains rather than pooling.
- Use fasteners rated for exterior and treated-lumber use to resist corrosion.
Fasteners are part of the material choice
The preservatives in modern pressure-treated lumber are more corrosive to metal than older formulations, so fastener selection is not an afterthought. Hot-dipped galvanized or stainless fasteners rated for contact with treated wood are the baseline. Hidden fastener systems are common with composite boards and keep the surface free of exposed screw heads, but they rely on consistent board gapping to work as intended.
Practical detail: If a deck sits in shade or under tree cover, it dries slowly and stays damp longer after rain. In those conditions, decay-resistant materials and generous drainage gaps matter more than they would on a sun-exposed deck.