Before you begin painting the exterior of your home, you should check the condition of the current paint job. Paint problems can be caused by flaws in the surface material, improper paint choices, incorrect painting technique, or a host of other issues. Knowing what went wrong before will help you to avoid going awry this time around.

This helpful chart will allow you to troubleshoot the various problems you may encounter with the existing surface. You'll see how they developed, and learn the best approach to fixing them and restoring a smooth, clean surface ready for painting.

Problem	Possible Cause	Solution
Peeling	Paint curls due to wet wood, interior moisture vapor, dirty, glossy surface.	Scrape, sand, prime, repaint. Install siding/soffit vents outside, exhaust fans inside.
Wrinkling	New paint sags and droops. Paint applied too thickly.	Scrape, sand, prime, and repaint. Stir new paint and brush out thoroughly.
Alligatoring	Paint dries into islands. Either due to incompatible paints or painting too soon over still-wet coat.	Scrape, sand, prime, and repaint with a compatible coating.
Blistering	Surface blisters caused by underlying moisture or solvent from paint applied on hot day.	Sand smooth, repaint. Install vents. Paint on mild days.
Chalking	Powdery residue stains on sidewalks, foundations. Inferior paint or porous undercoat to blame.	Wash down surface, let dry, repaint with nonchalking coating.
Mildew	Discoloration of exterior surface due to growth of fungus, usually black/green stains.	Scrub off with chlorine bleach or fungicide, let dry, repaint with mildew-resistant formula. Trim tree branches, shrubs.
Running sags	Wavy paint surface. Paint applied too heavily.	Sand smooth, repaint. Brush out paint to a consistent thickness.
Paint won't dry	Inferior paint.	Patience or removing and repainting. Test paints on small areas before painting entire house.
Efflorescence	Whitish deposits on masonry caused by moisture-induced oxidation.	Scrub off deposits with 10:1 water-muriatic acid solution, followed by 2:1 water-ammonia, water rinse, dry, repaint with appropriate masonry paint. Check downspouts, eliminate damp conditions.
Rust-stained siding/shingles	Rusting nail heads, gutters sealed insufficiently.	Seal rusting nail heads with rust-resistant sealer and paint entire surface.
Rusted metal	Deteriorated paint combined with moisture.	Scrape, sand, recoat with metal primer, metal paint.
Bleeding knots	Knot resin dissolved by paint solvent from improperly sealed, primed knots.	Scrape, sand to bare wood, coat with shellac, prime, repaint.

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