#1: Peeling from Masonry and Brick

CAUSE : A common cause of peeling on surfaces composed of mortar, brick, building block or concrete is efflorescence, where soluble salts are present. When dissolved by water, they are carried to the surface and remain after the water has evaporated. These salts can push paint away from the surface and peeling results. Efflorescence occurs on brick walls of new construction. A common building practice is to treat new brick or concrete with muriatic acid, rinsing with water to clean away excess mortar. Rinsing removes only those salts on or near the surface. After painting, salts remaining within the bricks will absorb the moisture and travel to the surface, causing peeling. Peeling can also occur when alkyd or oil paint is applied over unetched concrete. Alkyd resins that come in contact with an alkaline surface form a soap film between the concrete surface and the coating, called saponification. This will cause softness and loss of adhesion of the alkyd coating. SOLUTION : If efflorescence is evident, it must be removed before repainting. First, remove all flaking or chalking paint from the damaged area by wire brushing or sandblasting. If necessary, try applying a solution of 5% muriatic acid or undiluted vinegar. Rinse with clean water. Fill all cracks with masonry patching compound, latex concrete patch, or caulking compound. If the surface is very porous, apply an alkali-resistant primer or block filler. Cover with latex house paint. To prevent recurrence of efflorescence on interior walls, the exterior walls should be sealed. NOTE: Extraneous water sources must be removed before painting (e.g. migration at ground level, often caused by poor drainage).

#2: Peeling From Red Cedar or Redwood Siding

CAUSE : Mill-glaze occurs on smooth, flat-grained Western Red Cedar and occasionally on redwood. Controversy exists over the exact cause of this condition, but the general belief is that it occurs as a result of planing and/or drying the lumber. During the milling or planing process, overheating of the flat-grained smooth siding may bring water soluble resins to the surface creating a hard, varnish-like glaze. SOLUTION : If the surface is unpainted, it is advisable to roughen smooth siding slightly prior to priming. Two coats of primer may be necessary where severe staining exists. A waiting period of 24 hours after application of first primer coat is recommended before applying second coat and/or finish coat. Tannic acid stains will penetrate first coat of primer leaving brownish streaks or rings. Refer to "Cedar Stain" for additional information. If stains do occur, reprime stained spot and dry thoroughly before applying finish coat. For repainting over mill glaze problem areas, remove the failed coating areas by pressure washing or hand scrapping. Sand and prime as recommended above. Newly installed siding should be sanded and primed as soon as possible. Ultraviolet rays from the sun tend to degrade the integrity of the wood's surface. A 50% loss in adhesion occurs on western red cedar weathered for 16 weeks prior to finishing. Bare weathered siding should be sanded prior to coating to remove loose, dead wood fibers caused by extended exposure.

#3: Peeling from Galvanized Metal.

CAUSE : Improper priming of surface. Chemicals on new, unweathered galvanized surface. Rusting. When alkyd or oil-based product is applied over bare galvanized surface, a chemical reaction occurs and a soap film forms between metal and coating. SOLUTION : Remove all loose, flaking paint down to bare metal. Galvanized metal must be clean, dry, and free of oil or grease. Wipe new metal with mineral spirits to remove any oil film remaining from manufacturing operations.

#4: Cedar Stain (Tannic Acid Bleed)

CAUSE : Stains from red cedar, cypress, and redwood are due to a combination of moisture and insufficient sealing. Moisture carries water-soluble color extracts (tannic acid) contained in the wood through paint films. Staining is more likely to be visible when light or medium colors are used. It occurs more frequently with a latex coating than a solvent or oil based coating. SOLUTION : UNPAINTED WOOD: If staining occurs during paint application, use two coats of primer before top coating. A waiting period of 24 hours after application of the first primer is recommended before applying the second coat and/or finish coat. Tannic acid stains will penetrate the first coat of primer leaving brownish streaks or rings. If stains do occur, reprime the stained spot, allow to dry and apply the finish coat. Sometimes it is best for the new wood to weather for several weeks prior to painting. PREVIOUSLY PAINTED SURFACES: Stained areas can be washed with a one-to-one mixture of denatured alcohol and water. Wood bleach (oxalic acid) can also be used. Rinse treated areas well, let dry, then apply one coat of desired primer and topcoat.

#5: Blistering

CAUSE : Blistering refers to the formation of a blister caused by vapor expanding between the coated surface and the film. Due to humidity, construction defects, or lack of effective vapor barriers, moisture condenses on or saturates wood siding. Lower humidity and high temperature generate pressures within wood and on adhesive bond of the coating as trapped moisture evaporates. Solvent based coatings are most susceptible. Fresh blisters are filled with water. As the surface dries, water evaporates, but the paint film does not recover. Blistering is accelerated by the swelling effect of moisture on wood. Continued swelling and contraction between day and night humidity and temperature variations weakens adhesion. Another cause is solvent entrapment, or painting with solvent based coatings in direct sunlight on a surface that is too warm. This problem is prevalent in darker colors, due to absorption of heat, more than light colors. Thicker application or recoating prior to complete cure of a previous coat contribute to this type of failure. Under this condition, the paint surface dries before all the solvent is released from the underlying film. Expansion of trapped solvent produces blisters. SOLUTION : If blistering was caused by moisture, a number of solutions exist. Repair loose caulking and install vents or exhaust fans. If the home has lap siding, install siding vents. Vents or fans allow moisture from in the house to evaporate before penetrating wood siding. This will minimize future blistering problems. Sand and scrape peeling paint to bare wood. Prime exposed areas and repaint. If large areas of paint have blistered and need to be removed, high pressure washing or use of a heat gun will speed the process. Heat blisters develop in FRESHLY applied coatings only. When broken, they don't contain liquid and are not associated with a surface defect that requires remediation. These blisters may be removed by scraping and sanding. The surface should be recoated under more favorable conditions.

#6: Mildew

CAUSE : Mildew is NOT caused by paint. It is a fungus that grows on many surfaces including paint. Mildew discoloration is prevalent in warm, moist exposures, but can occur in most climates. Mold and mildew spores are microscopic particles transported by the wind. Spores can remain dormant on a surface until conditions are favorable for growth. Mildew-contaminated surfaces in neighborhoods can supply spores for contamination of other homes in the area. Mildew usually looks similar to dirt accumulation. However, on some surfaces it may appear as dark spots, or be concentrated in clusters. Under magnification a web like pattern is visible. Mildew is usually black or gray in color, but can also be dull red or yellow. To determine if mildew is present, drop a small amount of bleach on discolored surface. If mildew is present, bleach will destroy it and lighten the spots. If discoloration is simply dirt, bleach will have no effect. SOLUTION : Mildew MUST be removed before painting. Painting over mildew guarantees its return. Mildew will grow through paint films rapidly, and correction will then require removal of the coating! All mildew-stained surfaces should be washed with a solution of 1 or 2 cups of household bleach per gallon of warm water shortly before painting. Commercial mixtures for washing the surface are also available. Repeated applications may be necessary to completely remove discoloration. Repaint as soon as the surface is dry with a mildew-resistant paint. Multiple coats of quality products resist mildew growth longer than single coats. While there is no absolute cure for mildew, quality products will contain mildew resisting properties that can minimize its growth. Periodic examination and treatment of painted surfaces, in sound condition, with mildewcide wash will restore a freshly applied appearance to the film. Due to their composition, latex products are less likely to grow mildew than oil-based products.

#7: Peeling From Plaster Walls

CAUSE : Paint peeling from plaster could be the result chalking of the surface. This chalking can be caused by alkali, moisture, or insufficient wet troweling of the white coat. Another reason for peeling is the presence of a glue size (from removed wallpaper), which absorbs water, underneath the paint. SOLUTION : New plaster should be primed AFTER 30 days curing. This will allow for reduction in moisture and alkali content. After curing and before priming, the plaster should be wiped with a damp cloth to remove powder and dust. Peeling areas should be scraped down to a sound surface. Smooth the scraped edges with sand paper. If peeling is severe, then all the paint should be removed. Otherwise the remaining coating will peel, thus causing the new coat to fail. Cracks and holes in plaster should be repaired before repainting. If patching is necessary, a water-mix patch should be used when the intended topcoat is latex. Oil based patching compounds sometimes bleed into latex. When using a water-mix patch, thoroughly dampen the surrounding edges of the damaged areas to prevent the plaster from absorbing moisture and becoming crumbly. If the surface is badly disintegrated, mount canvas or "hardboard" over the plaster. Apply primer before and after filling cracks and holes. Sand when dry.