I've got a 1990s house with cedar siding that was stained years ago and now it's weathered gray and chalky.

Prep:

1. Test for lead (EPA RRP rule applies pre-1978; 1990s likely clear, but verify).
2. Wash: Pressure wash 500–800 psi max, fan tip, 12–18" distance. Use TSP substitute or dedicated siding cleaner. Rinse thoroughly. Let dry to ≤15% moisture content (meter check).
3. Remove chalk: After drying, wipe with dark cloth. If heavy chalk remains, re-wash or use a chalk-binding additive in first coat (e.g., Peel Bond, XIM Peel Bond).
4. Scrape/Sand: Remove all loose/flaking stain. Feather edges 80–100 grit. Do not sand to bare wood unless necessary; stain residue aids adhesion.
5. Repair: Replace rotted boards. Caulk only joints that were previously caulked (butt joints, trim interfaces). Do not caulk lap siding overlaps — traps moisture. Use polyurethane (ASTM C920 Class 25) or high-quality siliconized acrylic.
6. Spot prime: Bare wood, knots, stains — oil-based primer (see below).

Primer: Oil-based exterior wood primer (alkyd). Required over old stain/cedar.

• Blocks tannin bleed (cedar tannins bleed through latex).
• Penetrates chalky surface better than latex.
• Provides superior adhesion to weathered stain.
• Products: Zinsser Cover Stain, Benjamin Moore Fresh Start Oil (024), Sherwin-Williams WoodClassics Oil Primer.
• Application: Brush/roll worked into grain. One full coat. Dry 24 hrs (per label) before topcoat.

Topcoat: 100% acrylic latex, satin or low-lustre. Two coats. Back-brush/roll.

Critical: If stain is semi-transparent penetrating oil, oil primer is non-negotiable. Latex primer will fail. If siding is T1-11 or rough-sawn, back-brushing is mandatory.

Code/Ref: ASTM D3924 (oil primer), ASTM D4764 (latex topcoat), EPA 40 CFR 745 (RRP).

For a 1990s cedar siding that’s weathered gray and chalky, proper prep and priming are critical to ensure paint adhesion and longevity. Here’s the step-by-step process:

1. Clean Thoroughly

• Pressure wash at 1,500–2,000 PSI (use a fan tip, keep nozzle 12+ inches away to avoid wood damage).
• Apply a wood cleaner (e.g., oxalic acid-based like Wolman DeckBrite or a TSP substitute) to remove chalk, mildew, and grayed fibers. Scrub with a stiff nylon brush.
• Rinse well and let dry 48 hours (moisture content <15%).

2. Sand & Repair

• Lightly sand any fuzzy or raised grain with 80–100 grit sandpaper (hand or orbital sander).
• Replace any rotted, split, or severely checked boards. Cedar is prone to cupping—ensure proper flashing and drainage behind siding.
• Fill small cracks with exterior wood filler (e.g., Abatron WoodEpox); sand smooth.

3. Prime

• Use a 100% acrylic latex bonding primer formulated for tannin-rich woods like cedar (e.g., Zinsser Bulls Eye 1-2-3 Plus, Sherwin-Williams Loxon Concrete & Masonry Primer, or Benjamin Moore Fresh Start).
• Why? Cedar contains water-soluble tannins that bleed through standard primers, causing yellowish stains. A stain-blocking primer prevents this.
• Apply one coat per label directions (typically 1–2 mils wet film thickness). Back-brush or back-roll for penetration into rough-sawn cedar.
• Let dry 2–4 hours (per product) before topcoating.

4. Topcoat

• Apply two coats of 100% acrylic latex exterior paint (e.g., Sherwin-Williams Duration, Benjamin Moore Aura Exterior).
• Avoid oil-based paints—they trap moisture and fail faster on cedar.

Critical Notes:

• Never paint over chalky or loose surface—adhesion will fail.
• If tannin bleed appears after priming, spot-prime those areas with a shellac-based primer (e.g., Zinsser BIN) before topcoating.
• Check local codes: Some jurisdictions require vapor-permeable coatings on wood siding (IRC R703.2). 100% acrylic latex meets this.
• If siding is severely degraded or installed without a rainscreen, recommend consulting a builder—trapped moisture causes rot behind paint.

This system ensures adhesion, blocks tannins, and allows moisture escape. Skip steps, and you’ll see peeling in 1–2 years.