Should I Sand My Ottawa Cedar Deck Before Applying a Fresh Coat of Stain?

Cedar decks are gorgeous — and Ottawa has a lot of them. But cedar behaves differently from pressure-treated lumber when it comes to stain prep, and sanding is one of those steps where doing it wrong can actually make things worse. Let me walk you through when sanding is necessary, when it is not, and how Ottawa's climate plays into your prep strategy.

When You Should Sand Your Cedar Deck

Yes, sand if:

• The existing stain is peeling or flaking. Ottawa's freeze-thaw cycles — over 100 per year — are brutal on deck finishes. If you see curling paint chips or stain lifting away in sheets, you need to remove all the loose material. Sanding with 60 to 80 grit paper on a random orbital sander or pole sander is the most effective approach for spot removal. Follow up with 100 to 120 grit to smooth the transitions between bare wood and remaining stain.

• The wood surface feels rough, splintery, or has raised grain. Cedar is a softwood that develops fuzzy raised fibres after exposure to Ottawa's rain, snow, and UV. If you run your hand across the boards and feel roughness or catch splinters, a light sanding with 80 to 100 grit will knock down the high spots and create a smooth surface for stain to bond to.

• You are switching from a solid stain to a semi-transparent. The old solid stain must be completely removed, and sanding is part of that process (usually after chemical stripping). This is a big job — budget $4 to $7 per square foot if hiring a professional in Ottawa.

• There are grey, weathered patches. Cedar turns a silvery-grey when exposed to UV, and while some homeowners like that look, grey wood has a degraded surface layer that does not accept stain well. Sanding removes the dead surface cells and exposes fresh wood underneath that absorbs stain properly.

Do not sand if:

• You are recoating with a penetrating oil stain and the existing coat has worn away evenly. If the previous stain simply faded and thinned over time (no peeling or flaking), a thorough power wash and brightener treatment is usually sufficient prep. Sanding in this case can actually close the wood pores and reduce stain absorption.

• The wood is brand new cedar. New cedar has a natural smooth mill finish. Light sanding with 120 grit can help, but aggressive sanding burnishes the surface and creates a glazed layer that repels stain. If you do sand new cedar, keep it light.

• You are using a film-forming solid stain. These products sit on top of the wood rather than penetrating, so the surface just needs to be clean, dry, and free of loose material. A good wash and light scuff is sufficient.

The Ottawa-Specific Sanding Concerns

Our climate creates a few unique challenges for cedar deck prep:

Moisture content matters. Never sand cedar that is damp or wet — the sandpaper clogs instantly and you end up polishing the wood rather than profiling it. After Ottawa's spring thaw, cedar decks can retain moisture well into May. Test the moisture content before sanding; it should be below 15%. A moisture meter costs about $30 to $50 at any Ottawa hardware store and is worth owning.

Cedar's natural oils complicate things. Western red cedar contains thujaplicin, a natural preservative oil. In fresh cedar, these oils can prevent water-based stains from penetrating properly. Sanding helps by removing the oily surface layer, but washing with a cedar-specific deck cleaner (oxalic acid based) is equally important. Ottawa's long winters actually help here — by the time your deck has gone through one Ottawa winter, most of the surface oils have weathered away.

Watch for soft rot. Ottawa's humidity combined with persistent snow contact can cause soft rot in cedar — the wood feels spongy and punky when you press on it. If you find soft spots while sanding, stop and assess the structural integrity of those boards. Sanding soft-rotted wood is pointless; the boards need replacement. Typical cost for replacing individual deck boards in Ottawa: $15 to $30 per linear foot installed.

How to Sand a Cedar Deck Properly

Here is the step-by-step approach that Ottawa painting professionals follow:

Start with a deck cleaner/brightener. Apply a cedar-appropriate cleaner (products containing oxalic acid work best) and power wash at 1,000 to 1,200 PSI maximum. Cedar is soft — higher pressure damages the grain. Cost for a quality deck cleaner: $20 to $35 per gallon, covering about 200 square feet.

Let the deck dry completely. In Ottawa's summer humidity, allow 48 to 72 hours after washing. Do not rush this step.

Sand with the grain using 80 grit for heavy work or 100-120 grit for light prep. A random orbital sander is the safest choice because it prevents swirl marks. For large decks, a drum or belt floor sander is overkill and will eat through cedar too aggressively.

Vacuum or blow off all dust before staining. Dust left in the grain creates a barrier that prevents stain penetration. An electric leaf blower works well for this.

Apply stain within 24 to 48 hours of sanding. Freshly sanded cedar begins oxidizing and greying almost immediately in Ottawa's summer sun. The longer you wait, the more you lose the benefit of sanding.

Professional vs. DIY Sanding in Ottawa

DIY cost: Sandpaper and sander rental runs about $50 to $100 per day from Ottawa tool rental shops. A typical 250 square foot deck takes 3 to 5 hours of sanding work.

Professional prep and stain: Ottawa painters typically charge $3.50 to $6 per square foot for a full sand, clean, and two-coat stain job on cedar. That includes all materials and labour. For a 250 square foot deck, expect $875 to $1,500 total.

The professional route is worth considering for cedar specifically, because over-sanding is a common DIY mistake that leads to blotchy stain absorption. Experienced painters know how to read the wood and adjust their technique.

Need help finding a painter with cedar deck experience? The Ottawa Construction Network directory connects you with local contractors, and Ottawa Paint Contractors' Paint IQ can help you evaluate your specific deck condition before committing to a plan.