Common Painting Problems | Scholars Edge

Common Paint Problems

Diagnosis & Treatment


Patterned cracking in the paint film resembling the scales of an alligator. These cracks generally do not expose the substrate.
Possible Causes:
  • Natural aging of oil-based paints due to temperature fluctuation.
  • The constant expansion and contraction results in a loss ofpaint film elasticity.
  • Application of an extremely hard, rigid coating, like an oil enamel, over a softer, more flexible coating.
  • Application of a topcoat before the primer or basecoat is dry.
  • Application of a coating over a glossy finish.
  • Remove old paint by scraping, sanding, chemical removers, or a heat gun.
  • Follow all manufacturers’ cautions when using chemical removers or heat guns.
  • Remove all surface contamination by washing with an appropriate cleaner; rinse thoroughly and allow to dry.
  • Glossy surfaces should be sanded dull.
  • Follow label and data page directions for the appropriate drying time for any product.


Bubbles caused from a loss of adhesion and lifting of the paint film from the underlying surface.
Possible Causes:
  • Painting in direct sunlight on a surface that is too warm can cause heat blistering.
  • Moisture blistering can be caused by water migrating from the inside, through a wall to the exterior, pushing the paint off of the surface.
  • Application of oil-based or alkyd paint over a damp or wet surface.
  • Exposure of latex paint film to dew, high humidity, moisture, or rain shortly after paint has dried, especially if there was inadequate surface preparation and/or poor ventilation in areas such as kitchens and bathrooms.
  • Damp basements.
  • Moisture seeping into the home through the exterior walls.
  • Insufficient surface preparation, painting over a contaminant that the coating
  • If blisters go down to the substrate, the cause is likely to be moisture escaping from the surface. Remove all loose paint by scraping or other method and sand the surface to smooth out any rough edges. Determine and repair any cause of excess moisture before repainting.
  • Repair old or damaged caulking or install new caulking as needed, install vents or exhaust fans or siding wedges to allow the moisture a path to escape without going through the paint.
  • If blisters go down to an earlier coating, remove all loose paint by scraping or other methods, and sand the surface to smooth out any rough edges. Sand any glossy surface dull. Allow sufficient drying time after cleaning.

Caulking Failure

Loss of caulk’s initial adhesion and flexibility, causing painted caulk to crack and/or pull away from the surfaces to which it is applied.
Possible Causes:
  • Use of lower-quality caulk.
  • Use of wrong type of caulk for particular application (e.g., using latex or vinyl caulk in areas where there is prolonged contact with water or considerable movement of the caulked surfaces).
  • Not properly preparing or priming the surface prior to caulking.
  • Applying too thin of a bead of caulk.
  • Use a top-quality, water-based, all acrylic, or siliconized acrylic caulk or sealant if prolonged contact with water is not anticipated.
  • These caulks are flexible enough to adapt to minor fluctuations in the substrate, stretching in gaps that widen slightly over time.
  • They also adhere to a wide range of interior building materials, including wood, ceramic tile, concrete, glass, plaster, bare aluminum, brick, and plastic.
  • Proper surface preparation requires a clean surface; remove all surface contamination, old cracked or brittle caulk, loose or peeling paint.
  • In most cases, the surface should be primed to give the caulk a good surface to adhere to and to prevent the substrate from absorbing the liquid out of the caulk, which may cause improper drying and performance of the caulk.
  • Note: Pure silicone caulk should not be painted. When using semi-transparent finishes, caulks will be visible. Where possible, use a colored caulk to reduce this visibility.

Caulk - Paint Cracking or Crawling

The cracking of the paint film over a caulked area.
Possible Causes:
  • Some caulks are not paintable. Before using caulk, make sure it indicates paintable on the packaging. When paint is applied over a partially dried bead of caulk, the paint dries first, forming a film. As the caulk continues to dry, it shrinks causing the paint film to stretch and crack.
  • Applying caulk when the air, surface, or caulk temperature is below 40°F, and the caulk is not designed for these conditions.
  • Joints in excess of 1/2" in width or depth. If the opening is 1/4" or greater, for maximum performance, prevent three-point adhesion with backer rods or bond breaker tape. Three-point adhesion problems occur in cracks when the sealant adheres to the walls and the bottom of a crack, and a significant amount of flexibility is lost.
  • Prime first, then apply caulk only when temperature of surrounding air, surfaces to be caulked, and caulk are all above 40°F (or the recommended minimum temperature).
  • Do not apply when rain or freezing temperatures are expected.
  • Joints more than 1/2" should be filled within 1/2" of the surface with polyurethane rod or closed cell urethane foam.
  • Fill the remaining joint with caulk, and tool within five minutes of application.


The lifting of paint from the underlying surface in the form of flakes.
Possible Causes:
  • Flaking is generally preceded by cracking or checking, and will occur over different surfaces. Expansion and contraction of wood and plywood outside caused by temperature and humidity changes may cause a cracking in the surface that then gets transmitted through the coating.
  • On wood with an excessive amount of “flat” hard grain pattern, which is smooth, hard, and nonporous, there may be poor paint penetration; flaking can occur on these areas.
  • Flaking can also occur due to poor surface preparation and/or applying too thin a coat of paint.
  • Scrape, sand, or scrub with a wire brush to remove all loose and peeling paint.
  • Sand if needed to fresh wood.
  • Wood must not be allowed to weather prior to coating.
  • Follow label and data page directions for surface preparation for the coating drying time for any product.

Flashing / Uneven Gloss Retention

Deterioration of the paint film, resulting in excessive or rapid loss of gloss/luster of the topcoat. Uneven gloss/sheen/luster appearance of a coating.
Possible Causes:
  • Use of a gloss alkyd/oil-based paint or solvent-based epoxy in areas of direct sunlight.
  • Heavy dew, moisture, or condensation getting onto a coating while drying.
  • Temperature fluctuations during drying.
  • Coating over a porous surface.
  • Paint applied at uneven film thickness, lapping.
  • Insufficient film build.
  • Use of an interior paint outdoors.
  • Exterior alkyd/oil-based paints and solventbased epoxies will chalk, giving the appearance of loss of gloss. Washing the chalk off should return most of the original finish, but it will chalk again. If this is unsatisfactory, recoat with an acrylic following all label directions.
  • Bare substrates should be primed/sealed before applying the topcoat to ensure a uniform surface. Spot prime any patched areas to try to level off the porosity of the surface.
  • Often, applying an additional coat will even out sheen irregularities.
  • Thinning any touch-up coating may help it blend in better.

Lapping (Lap Marks)

Appearance of a darker/denser color or higher sheen where two layers overlap during paint application.
Possible Causes:
  • Failure to maintain a “wet edge” when painting. Essentially, some areas are receiving 2 coats.
  • Painting on an unsealed surface.
  • Painting under high temperatures.
  • Maintain a wet edge. When painting, apply paint in the unpainted area first and then back into the wet paint surface. This technique will produce a smooth, uniform appearance. Work in manageable-size areas; plan for interruptions at a natural break, such as a window, door, or corner.
  • Prime the surface with the appropriate primer to prevent the paint from soaking into the surface and drying too quickly. Follow label and data page directions for the appropriate environmental conditions. Begin rolling at a corner near the ceiling and work down the wall in threefoot- square sections.
  • Spread the paint in an “N” pattern, starting rolling from a dry area into the wet area. Cross-roll to fill in the “N”. Finish with light, downward, parallel strokes to uniform the finish.


Black, gray, green, or brown spots on any surface. Paint does not cause mildew.
Possible Causes:
  • Forms inside and outside, often on areas that tend to be damp or receive little or no direct sunlight.
  • Painting over a substrate containing mildew.
  • Test for mildew by applying a few drops of household bleach to the area, if it is bleached away, the discoloration is probably mildew; if it does not disappear, it is probably dirt. Remove before painting by washing with a solution of 1 part liquid bleach and 3 parts water. Apply the solution, and scrub the mildewed area.
  • Allow the solution to remain on the surface for 10 minutes. Rinse thoroughly with water and allow the surface to dry before painting. Wear protective eyewear, waterproof gloves, and protective clothing. Quickly wash off any of the mixture that comes in contact with your skin. Do not add detergents or ammonia to the bleach/water solution.
  • To protect against mildew, use a top-quality paint, and clean when necessary. Install an exhaust fan in high moisture areas. Use a product that contains agents that inhibit the growth of mildew on the surface of the paint film. If mildew is the only problem, after cleaning, painting may not be necessary.


Loss of adhesion of a coating to the substrate or an earlier coating. Where there is a primer and topcoat or multiple coats of paint, peeling may involve some or all of the coats.
Possible Causes:
  • Seepage of moisture through uncaulked joints or worn caulk.
  • Leaks in roof or walls, or excess moisture escaping through the walls from the interior.
  • Painting over a dirty, wet, or glossy surface.
  • Painting over a coating that already has marginal adhesion.
  • Remove old, loose, cracked caulk; prime as needed; and caulk with the appropriate product.
  • Find and repair any source of water.
  • Follow label and data page directions for proper surface preparation methods for the coating.
  • Test the coating surrounding any peeled areas out about 6" to 12" to be sure the adhesion is adequate.

Peeling - Due to Moisture (Outside)

Loss of adhesion of the paint film almost always down to the bare surface.
Possible Causes:
  • Worn-out or no caulking in joints, corners, and openings, allowing moisture to enter.
  • Ice-filled or clogged gutters, causing moisture buildup under the shingles.
  • Interior moisture migrating through to the exterior walls.
  • Painting surfaces which are too close to bare ground.
  • Leaking roofs.
  • Painting over a surface damp with rain, condensation, or dew.
  • Remove loose or cracked caulking, and repair with a quality product.
  • Clean and repair gutters so they properly channel water away from the house.
  • Install vents, louvers, fans, and dehumidifiers to relieve moisture, especially in the kitchen, bathroom, and laundry area.
  • If wood siding is touching the ground, remove that portion of the wood.
  • Siding should come down no further than 6" above the ground.
  • Repair the roof as needed.

Peeling - Window Sills & Frames

Loss of adhesion of the paint film (usually down to the bare surface) around window frames and sill.
Possible Causes:
  • Paint usually peels from window sills and frames because of moisture. Water standing on the sills eventually penetrates the paint film. When it later evaporates, the pressure from under the film causes peeling.
  • This moisture may be condensation on the interior, or rain and snow on the exterior.
  • Paint also peels from window sills due to poorly sealed framing that was not properly caulked; or the caulk has cracked or peeled away, allowing water to undermine the coating.
  • Remove as much paint as possible by scraping, sanding, chemical stripper, or heat gun.
  • Follow all manufacturers’ directions when using chemical strippers or heat guns. Test the If a wood surface is deteriorated, replace it using cedar, redwood, or pressuretreated coating surrounding any peeled areas.
  • Prime bare surface with the appropriate primer and caulk where necessary, especially at angles and crevices, to eliminate any opportunity for moisture to penetrate into the substrate. Do not seal or paint shut any vent holes in the window trim of storm windows.
  • The use of storm windows and dehumidifiers may help prevent recurrence of peeling.