What Preparation Is Needed Before Painting Cedar Siding on an Older Ottawa Home?

Cedar siding on an older Ottawa home is a beautiful feature — but it's also one of the most demanding surfaces to prep and paint properly. Cedar's natural oils, tannin content, and decades of Ottawa weather exposure create specific challenges. Rush the prep, and you'll be repainting in two years. Do it right, and your paint job will last 8-12 years.

Understanding What You're Working With

Ottawa homes built from the 1940s through the 1980s commonly feature western red cedar clapboard, shingles, or board-and-batten siding. After 40-80 years of exposure to Ottawa's freeze-thaw cycles, UV radiation, and over 200 cm of annual snowfall, you'll typically find:

• Multiple layers of old paint (some homes have 6-10 layers)
• Bare, greyed-out wood where paint has completely failed
• Tannin bleeding — dark brown/black stains that have bled through previous paint
• Raised grain from moisture cycling
• Soft or punky spots where rot has set in, particularly near the foundation, around windows, and on the north side
• Exposed nail heads that have rusted and stained surrounding wood

Every one of these conditions requires specific treatment. Here's the full prep sequence.

Step 1: Inspection and Rot Repair ($200-$800+)

Before anything else, walk the entire perimeter and probe the cedar with a screwdriver or awl:

• Press firmly into the wood every few feet, especially at the bottom edge of each board, around window and door frames, and at corner joints.
• Sound cedar resists penetration. Rotted cedar crumbles or the tool sinks in easily.
• Mark all soft spots with painter's tape.

Small rot areas (less than 6 inches) can be treated with epoxy wood consolidant ($25-$40 per kit) followed by epoxy wood filler ($20-$35 per quart). Larger sections need cedar board replacement — a skilled carpenter can splice in new cedar for $150-$400 per board depending on accessibility.

Do not paint over rot. Paint won't stop rot progression, and the failure will show through within one winter.

Step 2: Lead Paint Assessment

If your Ottawa home was built before 1978, there's a significant chance older paint layers contain lead. Ontario's Occupational Health and Safety Act and federal Consumer Product Safety regulations require safe handling:

• Use a 3M LeadCheck test kit ($15-$25 at Ottawa hardware stores) on any surface you plan to sand or scrape.
• If positive, do not dry-sand or heat-strip. Lead dust is a serious health hazard.
• Options: wet scraping with drop cloths for small areas, or hiring a lead-safe certified contractor for large-scale removal.

Professional lead-safe exterior prep adds $1,500-$4,000 to a project depending on home size. It's not optional if lead is present.

Step 3: Washing and Mildew Treatment

Power wash the entire surface at moderate pressure (1,500-2,000 PSI with a 25-degree tip). Cedar is softer than most siding materials — high pressure or a narrow tip will gouge the wood.

• Add a mildew-killing solution to the wash: 1 part bleach to 3 parts water, or a commercial product like Jomax or Mold Armor.
• Focus especially on north-facing walls, under eaves, and shaded areas where Ottawa's humidity promotes mildew growth.
• Allow 48-72 hours minimum drying time before proceeding. In Ottawa's spring or fall humidity, this may take longer. Use a moisture meter — cedar should read below 15% moisture content.

Step 4: Scraping and Sanding ($500-$2,000 labour)

This is the most labour-intensive step and the one that determines whether your paint job lasts:

• Scrape all loose, peeling, and flaking paint with a sharp pull scraper or carbide scraper. On older Ottawa cedar homes with multiple paint layers, this can remove 30-50% of the existing coating.
• Feather edges: Where old paint remains firmly adhered, sand the edges smooth so there's no abrupt ridge between painted and bare areas. Use 80-100 grit sandpaper.
• Sand bare wood lightly with 80-grit to remove surface grey and open the wood grain for primer absorption. Cedar's natural oils create a waxy surface layer on weathered wood that prevents paint adhesion — sanding removes this.
• Sand glossy old paint to create tooth for the new primer to grip.
• Remove all dust with a brush or clean cloth before priming.

Step 5: Tannin Stain Treatment

Cedar contains water-soluble tannins — natural extractives that cause dark brown or reddish-brown staining through paint. Ottawa's wet climate constantly activates these tannins. On a bare cedar board, you can see the brown discolouration where water has run.

To prevent tannin bleed-through:

• Use an alkyd (oil-based) stain-blocking primer — this is non-negotiable for cedar. Latex primers do not block tannin effectively.
• Recommended products: Zinsser Cover Stain ($25-$35/gallon), Kilz Original ($22-$30/gallon), or Benjamin Moore Fresh Start alkyd primer ($35-$50/gallon).
• Apply one full coat to all bare wood and any areas showing previous tannin bleed.
• If staining is severe, a second primer coat may be needed.

Skipping the alkyd primer and using latex primer on cedar is the most common cause of brown stains showing through fresh white or light-coloured paint on Ottawa homes. I see it constantly.

Step 6: Caulking and Sealing

• Caulk all joints: Where siding meets window and door trim, at corner boards, and where siding meets the foundation. Use paintable exterior silicone-modified caulk ($5-$8/tube).
• Replace missing or cracked putty around window glazing on older wood-frame windows.
• Set exposed nail heads slightly below the surface with a nail set, then fill with exterior wood filler.
• Replace any rusted nails with stainless steel ring-shank siding nails that won't rust and stain.

Step 7: Priming

• Bare wood: Alkyd stain-blocking primer (see Step 5).
• Previously painted surfaces in good condition: A bonding primer or simply scuff-sand and apply top coat.
• Allow primer to cure according to manufacturer directions — typically 24 hours for alkyd primers.

Step 8: Top Coat Application

• 100% acrylic latex in your chosen colour and sheen. Satin or semi-gloss for trim, flat or low-sheen for siding is the typical Ottawa preference.
• Two full coats: This is not optional on cedar. The naturally textured surface absorbs more paint than smooth siding, and a single coat leaves thin spots that fail first.
• Paint in the right conditions: Surface temperature 10-30C, humidity below 80%, no rain for 24 hours.

Total Cost Estimate for Ottawa

For a typical 1,500 sq ft older Ottawa home with cedar siding:

| Component | DIY Cost | Professional Cost |
|-----------|----------|------------------|
| Rot repair | $100-$300 | $400-$1,500 |
| Washing | $50-$100 | $200-$400 |
| Scraping/sanding | Your time | $1,000-$3,000 |
| Primer + paint (materials) | $400-$700 | Included below |
| Full professional job | N/A | $5,000-$10,000 |

These are Ottawa prices — roughly 10-15% below Toronto for equivalent work.

For experienced painters who specialize in older cedar homes, the Ottawa Construction Network directory is a solid starting point. And Ottawa Paint Contractors has dozens of Paint IQ answers covering cedar care, heritage home painting, and other topics specific to Ottawa's housing stock.