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Algae are green chlorophyll-containing organisms that obtain their nutrition by photosynthesis. Like mildew, algae will flourish where there is an adequate source of moisture. It grows almost exclusively outdoors. Cement-based products are more prone than other substrates to support algae growth.
Provide drainage to rid immediate area of excess ground moisture. Locate and correct source of moisture that is saturating vertical surfaces. Remove algae growth with a soft brush and household bleach. Flush area with clean water and allow to dry thoroughly. Remove loose paint to a sound surface. Sand weathered wood to fresh wood.
Caution: Wear a face mask to prevent inhalation of dust particles during the sanding procedure.
One coat of A-100 Alkyd Exterior Wood Primer
Two coats Exterior Latex House and Trim Paint |
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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.
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.
Use a protective face mask to avoid inhalation of fumes and dust during paint removal.
Prime bare wood with A-100 Exterior Latex or Alkyd Wood Primer
Two coats of Exterior Latex House and Trim Paint |
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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.
Remove loose paint with pressurized water.
Scrape areas that are loose but resist removal by water blasting.
Eliminate moisture by determining the need for:
a. Caulking - cracks, holes and seams
b. Wedge vents
c. Attic louvers
d. 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.
Prime bare wood with Sherwin-Williams A-100 Latex or Alkyd Exterior Wood Primer
Note: Use Alkyd Undercoater on woods such as redwood or cedar which will cause staining of the topcoat.
Apply two coats of Sherwin-Williams topcoat, preferably latex.
Note: When painting between 35 degrees F and 50 degrees F or when the temperature is expected to drop to between 35 degrees F and 50 degrees F within 48 hours of painting, apply two coats of LowTemp 35 Acrylic Latex House Paint after priming with one coat A-100 Exterior Wood Primer. |
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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.
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% acrylic coating will give the best service performance.
Flat latex 100% 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.
One coat Loxon Exterior Acrylic Masonry Primer
Two coats Loxon Exterior Acrylic Masonry Paint |
