Cause

Alligatoring and cracking is caused by excessive build up of paint. Eventually, multiple cracking of the paint film occurs as seasonal temperature variations inhibit expansion and contraction of the paint film with the substrate. Simultaneous to cracking, the inability of the thick paint film to expand and contract with the substrate results in adhesion loss. Paint applied to this surface will invariably accelerate flaking of the total film down to the substrate.

Wrinkling is caused by applying paint in excess of the recommended wet film thickness and by applying paint containing strong solvents to already dry paint films. These solvents cause the underlying paint film to dissolve and expand (wrinkle) under the newly applied paint. The result is a wrinkled finish.

Solution

Wrinkled surfaces can be power-sanded to a smooth surface. Surfaces that show alligatoring or cracking must have the paint stripped to bare wood by power sanding, use of paint remover, or heating gun and scraper.

Bare wood that has been exposed to weathering must be sanded to fresh wood. Exposure of sanded fresh wood to sunlight for more than a one-week period will result in peeling of the newly applied paint.

Recommended:

Prime bare wood with Exterior Latex or Alkyd Wood primer
Two coats of Exterior Latex House & Trim paint

Cause

Moisture.

Poor surface preparation by failing to remove chalk residue.

Factory primer on new substrate is hard, glossy or contaminated.

Application of latex paint below minimum application temperature.

Solution

Remove loose paint with pressurized water. Scrape areas that are loose but resist removal by water blasting.
Eliminate moisture by determining the need for: caulking-cracks, holes and seams wedge vents, attic louvers, exhaust fans

Scrape off paint from problem area and then sand to fresh wood, feathering edges.

Note: Composition board or hardboard must be sanded carefully to avoid damaging the surface. Use extra precautions when removing paint film from these surfaces.

Recommended:

Prime bare wood with Latex or Alkyd Exterior Wood primer

Apply two coats of topcoat, preferably latex.
Note: When painting between 35ºF and 50ºF or when the temperature is expected to drop to between 35ºF and 50ºF within 48 hours of painting, apply two coats of Latex House paint after priming with one coat Exterior Wood primer

Cause

Stucco and mortar joints contain hydrated or "hot" lime, a dry compound added to improve the workability of these materials. Different mortars are compounded with different amounts of “hot” lime, depending on the end use of the mortar. This problem is then made worse by more “hot” lime being added at the job site.

The alkalinity of mortar, cement mixes and concrete is expressed numerically by pH readings. The pH of fresh cementitious materials is 13 to 14. It takes approximately 30 days for fresh cement materials to drop to an approximate pH of 9. A pH of 9 is less alkaline than a pH of 13, and a coating has a greater assurance of success when applied to a less alkaline surface.

Once these cement walls are cured, the introduction of moisture into these walls will reactivate the high pH alkalinity, resulting in efflorescence, blistering and peeling of the paint film.

Solution

When damp areas are found on old surfaces, the source of moisture intrusion must be repaired. The surface should then be prepared by removing chalk, efflorescence and damaged paint film, and must be thoroughly dry before applying new paint.

Both new and aged unpainted walls must be clean and free of moisture and efflorescence. (See Efflorescence for description and resolution.)

Paint products must be chosen with care. The alkalinity of "hot" surfaces will destroy an alkyd or oil product within 6 months. A vinyl acrylic coating will perform slightly better; however, it will ultimately fail. A 100 percent acrylic coating will give the best service performance.

Flat latex acrylic coatings will perform best because of their ability to allow vapor transmission through the dry paint film. Non-permeable films (e.g., gloss paints) may blister when applied over the same damp condition.

Note: Composition board or hardboard must be sanded carefully to avoid damaging the surface. Use extra precautions when removing paint film from these surfaces.

Recommended:

One coat Exterior Acrylic Masonry primer
Two coats Exterior Acrylic Masonry paint

Cause

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 separates from the underside of the paint film. Ultimately, the paint film cracks.

Conditions that affect the drying time for caulks are air, surface or caulk temperatures below 40ºF; high humidity; and joints in excess of 1/2" in width or depth.

Solution

Surfaces to be sealed should be sound, dry, and free of oils, dust, mortar spatter, release agents, old caulk, bitumen, old paint or other contaminants. Remove flaky, loose and powdery material from the joint.

Apply caulk only when temperature of surrounding air, surfaces to be caulked and caulk are all above 40ºF. Do not apply when rain or freezing temperatures are expected.

Joints should not be more than 1/2" in width or depth. Joints deeper than 1/2" should be filled within 1/2" of the surface with polyethylene rod or closed cell urethane foam. Fill the remaining joint with caulk, and tool within five minutes of application.

Recommended:

One coat Latex or Alkyd Exterior Wood primer
Two coats Exterior Latex House & Trim paint

Cause

Slight chalking of a weathered paint film is normal and desirable. Application of new paint over severe chalk will cause peeling problems.

Aluminum siding can develop an excessively thick chalk layer and will require power washing to insure complete chalk removal.

Solution

Remove chalk by washing siding with detergent and water. If some chalk remains after first washing, wash again for complete removal. Rinse well with clear water. Allow to dry thoroughly.

Recommended:

Aluminum siding (flat or smooth)

Two coats Exterior Latex House & Trim paint (flat or satin only)
- Aluminum siding (embossed)
Two coats Exterior Latex House & Trim paint (flat, satin or gloss)
Caution: gloss paint on smooth aluminum siding will magnify metal imperfections when viewed at low angles.

Caution: Wear a face mask to avoid inhalation of dust particles during the sanding procedure.

Cause

Darkening of wood is caused by ultraviolet radiation. This can take place on wood that has never been coated with a protective coating. It also can occur under clear varnishes and lightly pigmented stains. Different degrees of darkening can occur on different woods. If moisture penetrates into the wood, varnish coatings will peel due to wood decomposition under the coating. Woods that are exposed to weather are not protected against wood-destroying organisms. Eventually the wood ceases to be a coatable surface.

Solution

New woods must not be exposed to harmful sunrays for extended time periods. Paint and stain adhesion performance is enhanced when the new wood is painted or stained immediately after installation. Wood that has been allowed to darken (decompose) must be sanded to fresh wood. Wood that cannot be sanded to fresh wood must be replaced.

Coatings can be applied to treated woods after the moisture content has dropped to a paintable level. Semi-transparent stains must be used on all horizontal (walk-on) surfaces. Paints, semi-transparent and solid color stains can be used on vertical surfaces.

Recommended:

Two coats Exterior Acrylic Solid Color stain
or
One coat Alkyd Exterior Wood primer
Two coats Exterior Latex House and Trim paint (flat, satin and gloss)
- Decks and Porches (walk-on areas)

Cause

Discolouration encompasses all types of surface related effects that lead to unexpected color changes. These include a darkening or gray color from surfactant leaching, white efflorescence on masonry, white or black color over caulk, black color over masonry patches and drywall joint compounds, red color (tannin bleed) over cedar and redwood, brown or black color (wax bleed) over hard board, yellowing of white paints, a wide range of color change when non-durable organic pigments are used as tinting colorants, and a premature loss of color when paints are applied over heavy chalk residue.

Solution

Colour changes are used as indicators for determining the cause of the problem. Some can be paint related, while others are substrate (or surface) related. Color change does not mean that the protective quality of the paint film has been altered.

Recommended:

Two coats Exterior Latex House & Trim paint

Cause

Efflorescence is often seen as a white fluffy deposit of salt crystals on cementitious wall surfaces. It depends on the presence of salt and moisture. The growth of crystals will continue as long as both are present. The salts are present in the mortar blocks or concrete structure and the moisture is usually attributable to some building defect. When emanating from mortar in brick or block buildings, efflorescence will appear as narrow bands corresponding to mortar joints.

Solution

Painting should be delayed if efflorescence continues. Salts should be removed by mechanical brushing. The use of water to remove efflorescence will only aggravate the defect. Repair areas where moisture penetrates the wall. Allow walls to dry thoroughly.

Caulk all areas such as nail heads, holes and butt joints.

Recommended:

One coat Exterior Acrylic Masonry primer
Two coats Exterior Acrylic Masonry paint

Cause

Colours will fade slightly when exposed to intense sunlight. As the coating ages, the fading can become more noticeable. Slight fading is acceptable provided it is gradual and uniform so as not to be noticeable. Excessive chalking of the paint film will cause colours to appear lighter.

Solution

When substrate is in good condition except for fading, remove dirt and chalk as recommended. Topcoat with house paints which are color-fast. Latex topcoats have especially good resistance to color fading.

Recommended:

Two coats Exterior Latex House & Trim paint

Caution: Organic red and yellow universal colorant is to be used for interior colors only.

Cause

Flaking is the lifting of paint from the underlying surface in the form of flakes. It is generally preceded by cracking or checking and will occur over different surfaces. When it occurs over wood, it is usually found on those boards that have an excessive amount of “flat” hard grain pattern. This flat grain pattern is smooth, hard and non-porous. Highly pigmented paints crack and eventually flake when applied to this type of surface. They cannot accommodate the large extremes of expansion and contraction of the wood that are caused by seasonal weather changes. Because of poor paint penetration into the hard flat grain, flaking will occur on these areas.

Solution

A light sanding to fresh wood followed by application of a high quality under-coater is recommended. Wood must not be allowed to weather prior to coating. Replace boards that have an excessive amount of flat grain patterns with boards that have an edge grain (e.g., boards with equal amounts of narrow hard and soft grain patterns).

Recommended:

One coat Alkyd or Latex Exterior Wood primer
Two coats Exterior Latex House & Trim paint

Cause

Frosting is the formation of white surface crystals on paint surfaces. When present, these crystals are most noticeable on dark colors and form in areas that are protected from the cleansing action of rainfall. The crystals form when the paint is exposed to excessive moisture (dew, condensation, rain, etc.) or cool temperatures during the curing process and create a surface condition called "frosting."

Solution

Apply paint to all surfaces during climatic conditions that allow proper curing of the paint film. If frosting occurs use a garden hose to flush crystal formations with warm tap water. Water-soluble crystals will disappear. Follow-up water flushing may be required at later dates and eventually crystal formation will cease. If crystals are not water-soluble, then other actions are required. Allow surface to dry thoroughly. Using medium grit sanding paper, lightly sand crystals away until original color of paint film reappears. Remove all loose dust and apply a uniform coat of Alkyd Wood Primer. This alkyd undercoat will act as a barrier coat preventing the formation of future frosting. Apply latex or alkyd topcoat.

Recommended:

Alkyd Wood Primer undercoat & latex or alkyd topcoat

Cause

As a rule, paints do not adhere well to smooth metal surfaces. Galvanized metal, a product used to make corrugated sheets, gutters and downspouts, is not only smooth, but the metal is coated with a thin to heavy layer of oil to prevent white rust.

When oily galvanized steel is painted during cold and highly humid conditions, the curing of the paint film is retarded, resulting in wrinkling and loss of adhesion (see insert).

Alkyd paints that are applied to galvanized metal will produce an acceptable paint film initially, but will quickly fail. The zinc of the galvanize will chemically react with the alkyd binder of the paint, which leads to extreme paint peeling.

When galvanized metal is allowed to remain exposed to the atmosphere, the protective zinc metal coating will oxidize into a white rust until eventually the zinc metal is depleted. The underlying steel will then rust to the offensive red colour.

Solution

The protective layer of oil must be completely removed. Solvent wiping using a water soluble cleaning agent or VM&P naphtha is recommended for small manageable areas. Many solvents, including mineral spirits, leave a thin layer of residue which leads to adhesion failure of the paint film.

Weathered galvanize develops a layer of "white rust" which must be removed to ensure good adhesion of the applied paint. Wire brushing is recommended.

Iron rust must be removed by wire brushing followed by sanding with a productive grit sandpaper. Severely rusted gutters should be replaced.

Recommended:

Galvanized (new)

Two coats Exterior Latex House & Trim paint

Galvanized (weathered)

Two coats Exterior Latex House & Trim paint
Galvanized (red rust)

One coat primer/finish
Two coats Exterior Latex House & Trim paint

Caution: When removing "white rust," wear a face mask to avoid inhalation of dust particles.

Cause

Many different water-soluble materials are used in the manufacture of latex emulsion paints. When these paints are applied during hot and humid periods and expected to dry during cool evenings, the painted surface will cool, allowing dew to form. This accumulated moisture on a paint surface whose curing is temporarily delayed will extract and concentrate different water-soluble materials from within the paint at the paint surface. As the water evaporates, a concentrated residue is left behind, causing staining, unsightly runs and gloss patterns.

Aluminum siding will react to temperature changes faster than solid wood siding because of the smaller amount of material involved. Consequently, aluminum siding will develop surfactant leaching quicker and more easily; however, all siding is prone to this problem under identical conditions.

Solution

Apply paint to all surfaces during climatic conditions that allow proper curing of the paint film. When “surfactant leaching” happens, flush with clean water immediately before the stains have sufficient time to set up or harden. Light scrubbing with a soft brush is acceptable. If stains cannot be removed in this manner, then repainting will be necessary during more favorable weather conditions.

Recommended:

One coat Exterior Latex House & Trim paint

Cause

The appearance of mildew depends on various conditions, which are: continuously high humidity. As the humidity increases, mildew growth becomes more rapid.
high average temperature. Optimum temperature for mildew growth is 77ºF.
poor ventilation. Still air increases mildew growth.
composition of surface. Mildew will grow on any surface that provides a nutrient, even dirt.
light colors of paint film. Colors that do not absorb the sun’s heat provide a surface for mildew growth. Dark colors become hot and discourage mildew growth.

Solution

Wash mildewed areas with a solution of one part household bleach and three parts water.1 This will destroy mildew and bleach stains caused by mildew growth. Apply solution by brush or a garden sprayer apparatus. Heavy mildew may require additional applications, and scrubbing may be required. Flush area with clean water to remove bleach solution. Allow to dry thoroughly.

Recommended:

Spot prime bare areas
Two coats Exterior Latex House & Trim paint
Note: If mildew growth is excessively heavy, add additional mildewcide to paint for added protection.

Caution: Follow label cautions when using bleach solution.

Cause

Peeling is caused by poor surface preparation, and refers to the removal of strips or sheets of paint due to loss of adhesion. The loss of adhesion could be the result of:

painting over a coating containing wax;
an excess buildup of moisture within the wood;
painting over an old, smooth coating; or
painting over heavy chalk surfaces.
Other surface conditions or contaminants known to affect the adhesion of newly applied topcoats are oil, grease, various forms of pollution such as dust, dirt and mildew, applying paint over hard glossy surfaces and excessively thick film topcoats.
Peeling may also be the result of applying latex paint below its recommended application temperature

Solution

Proper surface preparation will prevent peeling of the topcoat. If a peeling situation persists, the loose paint must be completely removed. Prepare surface by removing or abrading the problem surface. Sand all bare wood to fresh wood.

Remove surface contaminants with naphtha solvent, detergents and water. Glossy surfaces must be scuff sanded. All surfaces must be rinsed with clean water and allowed to dry thoroughly. Exposed wood areas must be sanded to fresh wood and primed with an alkyd or latex primer.

Caution: Wear a face mask to avoid inhalation of dust particles during the sanding procedure.

Recommended:

One coat A-100 Exterior Wood primer
Two coats Exterior Latex House & Trim paint
Note: When painting between 35ºF and 50ºF or when the temperature is expected to drop to between 35ºF and 50ºF within 48 hours of painting, apply two coats of Low Temp 35 Acrylic Latex House paint after priming with one coat A-100 Exterior Wood primer.

Cause

Plywood cracks from its expansion and contraction with changing moisture content. Plywood is prone to cracking because of its original method of manufacture involving peeling thin sheets of wood from logs. Stresses are induced which later show up as cracking. Many small fissures are produced in films of paints and stains that have been applied to insufficiently dry plywood. The edges of these cracks protrude upward and can be felt as sharp burrs. Subsequently, this coating may become detached from the edges of the cracks and lead to flaking.

Solution

New wood: To prevent cracking of newly installed plywood, sand and prime with Sherwin-Williams Latex Exterior Wood primer.

Repaint: If cracking is severe, replace the wood, for this is an unpaintable surface.

If the cracking is not extensive, sand surface smooth. The plywood must be thoroughly dry. Apply latex primer.

Caution: Wear a face mask to avoid inhalation of dust particles during the sanding procedure.

Recommended:

New wood

One coat Latex Exterior Wood primer
Two coats Exterior Latex House & Trim paint
Repaint
Spot prime with Latex Exterior Wood primer
Two coats Exterior Latex House & Trim paint
Note: Tint primer to compliment topcoat color. Do not use white primer under dark colors since future cracking of the topcoat will disclose a white pattern

Cause

The most common surface to show this failure is plywood that has been stained with a semi-transparent or solid color alkyd stain. The reasons for plywood separation are the same as those discussed in “Plywood Cracking”, as they relate to moisture content, method of plywood manufacture and induced wood stress. The main difference is that although the coating cracks, it does not peel and lead to flaking. Instead, the wood is open for moisture intrusion from outside weather conditions, leading to delamination and deterioration of the plywood.

The wood is highly textured, allowing water to remain on the total surface for extended time periods. These woods are designed for staining and since plywood cracking is inevitable, the life of the coating is shortened. Pigmented stains penetrate the porous wood surface, allowing very little of the stain to remain on the surface. Subsequently, as the wood cracks, the applied stain also cracks.

Solution

Using detergent and water, scrub siding to remove old oxidized paint film, dirt and other contaminants. Flush with clean water and allow to dry thoroughly. Fill large holes found in plywood grooves with colored caulk to prevent further water intrusion.

Caution: Wear a face mask to avoid inhalation of dust particles during the sanding procedure.

Recommended:

Two coats solid color Alkyd or Latex stain
or
Two coats of Exterior Acrylic Solid Color stain

Cause

Steel nails that are in contact with moisture will rust. Depending on conditions, this rust can either be red or black. Nail heads exposed to air will always be red rust colored. If the nail is extracted and the nail shank is red, then the wood is saturated with moisture. Damp wood that possesses a high amount of tannic acid may develop black discoloration if it comes in contact with steel. Nail heads that are a black color are usually under the coating surface and will ultimately cause adhesion failure of the topcoat. Once exposed, the nail head will develop red rust.

Solution

Locate and eliminate the source of moisture. Replace nails with galvanized or other non-rusting nails. Rusty nails that cannot be removed must be sanded to shiny metal, countersunk, coated with a rust-preventive primer and then caulked. Repair moisture damage by sanding weathered wood to a fresh surface.

Recommended:

Spot-prime exposed wood and caulked nail heads.
One coat Alkyd Exterior Wood primer
Two coats Exterior Latex House & Trim paint