Our 1970s Vancouver home has cedar siding and every time we repaint, reddish-brown stains bleed through within a year. What are we doing wrong?

You're dealing with tannin bleed, which is one of the most persistent paint problems on Vancouver's many cedar-clad homes. Western red cedar is prized for its beauty and rot resistance, but it contains natural tannins that dissolve in water and migrate through paint films, causing those reddish-brown discolourations.

The problem is almost certainly inadequate priming. Standard latex primers cannot block cedar tannins. You need a dedicated tannin-blocking primer, and there are two reliable options. Shellac-based primers like Zinsser BIN are the most effective tannin blockers available. Oil-based alkyd primers are the second-best option and are easier to apply on large exterior surfaces. Some newer high-quality acrylic stain-blocking primers also perform well, but check that the product specifically mentions tannin blocking on cedar.

The prep sequence matters too. Power wash the siding to remove chalked old paint, dirt, and surface tannin deposits. Let it dry thoroughly, which in Vancouver's climate means waiting for a stretch of dry weather, ideally in July or August. Sand any rough areas. Apply one full coat of tannin-blocking primer to bare wood and any stained areas. Then apply two coats of quality exterior acrylic latex paint.

Another factor is your siding's exposure to rain splash and moisture. Cedar siding on north-facing walls or near ground level gets far more tannin bleed because moisture drives the tannins outward. Ensure your landscaping and grading direct water away from the siding.

As a next step, schedule your exterior repaint during Vancouver's dry summer window and insist that your painter uses a shellac-based primer on all bare wood and previously stained areas.

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