How to Clean and Paint Over Ceiling Water Stains

Water stains are the unwelcome scars of past plumbing leaks or roof drips. Even after you have addressed the source of the moisture, the yellow or brown halo left behind serves as a persistent reminder of the event. A simple coat of standard ceiling paint is rarely enough to hide these stains; the tannins will bleed through almost immediately, leaving you right back where you started. Successfully erasing these marks requires a two-pronged attack. You must kill any potential mold spores with a cleaning agent and then seal the surface with a high-performance stain-blocking primer. Once the foundation is locked down, the finish paint will sit clean and crisp, finally allowing the ceiling to disappear back into the background of your living room.

Check for moisture first. Touch the stained area to ensure it is completely dry to the touch. If the drywall feels soft, spongy, or damp, you must stop and fix the underlying leak before proceeding.
Kill mold and contaminants. Mix a solution of one cup bleach to one gallon of water. Lightly sponge the stained area to remove surface contaminants and kill mold spores, then let it dry thoroughly.
Feather edges smooth. Use a putty knife to gently scrape away any bubbling paint or loose joint compound around the stain. Lightly sand the edges with 120-grit sandpaper to feather the transition.
Seal with oil-based primer. Apply a coat of oil-based or shellac-based stain-blocking primer over the stain. Extend the coverage at least two inches beyond the edge of the discoloration to ensure full encapsulation.
Wait for full cure. Allow the primer to dry according to the manufacturer's instructions, usually between one to four hours. The stain should be completely hidden beneath the primer layer before you move to the topcoat.
Blend with existing paint. Apply your finish coat using a roller, feathering the edges into the existing ceiling paint. If the ceiling is aged, you may need to paint the entire section to avoid a visible patch.