We want you to identify and fix minor or major problems with exterior paint, such as blistering, chalking, efflorescence, alligatoring, and checking. However, there are a number of frequent difficulties that occur with outdoor paint jobs under particular conditions—or when the preparation or application was less than optimal. Understanding the causes and solutions to these typical difficulties can assist you in dealing with them swiftly and avoiding them in the future.
Paints that cover external siding and trim surfaces confront some of the most demanding conditions available, including searing sun exposure, regular rain soaks, and drastic temperature swings. Modern paint chemistry makes today’s paints surprisingly adept at dealing with these circumstances, and house surfaces that historically required painting every two or three years can now go up to a decade without needing to be repainted.
Paint that Blisters
If you see small to medium-sized bubbles or blisters under the paint coat, it indicates blistering paint. It is most frequently found on wood siding and trim.
Possible Root Causes
Paint was sprayed to a hot surface under bright sunlight, trapping solvent vapor as the paint dried too quickly. When the paint was applied, the retained moisture in the wood caused the paint layer to expand.
After latex paint cured, dew, rain, or extremely high humidity penetrated—a common problem if the latex paint was of poor quality or the substrate surface preparation was inadequate. House moisture escaped through the walls as a result of poor ventilation.
Repair and Maintenance
Scrape away blistered paint and sand the surface to bare wood. Allow the wood to thoroughly dry before painting. Sand, prime, and paint in a non-humid environment and out of direct sunlight. Make use of high-quality latex paint.
Corrective repairs must be undertaken to properly ventilate the home’s walls, roof, eaves, bathrooms, and so on if there is a shortage of home ventilation. Examine and fix any missing or loose caulking around windows and doors. Consider adding ventilation to the siding.
Chalking
The thin chalky powder that accumulates on the surface of a paint film identifies chalking. Although some chalking is natural when paint is exposed to sunlight and rain, excessive chalking can signal paint failure. Chalking can become extreme in dry arid settings with little rain. Chalking is actually paint pigment liberated by paint binders that have degraded due to weather exposure. Chalking is most frequent with very light-colored flat paints, particularly lower-quality oil-based paints with large quantities of pigment extenders. When the chalking becomes too severe, it may run off and taint the surrounding structure.
Possible Root Causes
- Cheaper-quality exterior paint with large quantities of pigment extenders was employed.
- In an outdoor application, improper paint (such as inside paint) was employed.
- Over lower-quality factory-finished metal siding, paint was added.
- Before applying the paint, it was over-thinned.
- Before painting, porous surfaces were not thoroughly sealed.
Repair and Maintenance
Before repainting, the chalking must be removed. Power wash or scrub with a trisodium phosphate cleaning solution to remove chalking, then rinse with clean water. Allow to dry before painting with a high-quality latex home paint.
To clean brick areas soiled by chalking runoff, use a specific masonry cleaning solution to scour the masonry. If the staining persists, the brick may need to be cleaned by a professional cleaning contractor.
Efflorescence
Efflorescence, an issue of painted masonry building, is distinguished by crusty white salt deposits bubbling through the paint coat from an underlying masonry structure. Salts in the brick or concrete dissolve in water and then leach to the surface as the water evaporates.
Possible Root Causes
- Prior efflorescence was not completely cleaned and washed before the surface was repainted, resulting in inadequate surface preparation.
- Heavy moisture traveled from the inside of the house through the outer brick walls.
- Basement walls that were not fully waterproofed allowed groundwater to enter.
- If masonry was painted before the concrete or mortar had sufficiently dried and hardened.
- Water has gotten behind the stone wall due to cracks in the masonry or inadequate tuckpointing.
Repair and Maintenance
If moisture is entering into the masonry wall, fix the cause by properly tuckpointing any cracks or missing mortar in the wall or fixing concrete with a latex concrete patch. Then clean out gutters and downspouts, and caulk joints around windows and doors with butyl rubber caulk.
After that apply waterproofing to the outside of the wall if moisture is migrating through it from the outside (e.g., basement wall).
Remove all efflorescence and any flaking, chalking paint with a wire brush, scraping, or power washing. Then, rinse with clean water after cleaning with a trisodium phosphate cleaning solution. Allow to dry completely before priming and painting with a high-quality latex house paint.
Alligatoring and Cracks called Checking
When the paint surface develops a fractured pattern with deep relief that resembles the skin of a reptile, it is called alligatoring. Checking is a less severe breakdown that is characterized by lengthy, somewhat regularly spaced cracks in the paint film with shallow relief or depth. Checking can become severe in some spots, resulting in a deeper fracture or split in the paint.
Possible Root Causes (Alligatoring)
The second coat of paint was placed over the partially cured first coat of primer or paint base coat.
Another coat of paint was applied over an incompatible paint, for example a glossy paint, over a latex-based paint, or a hard oil enamel over a glossy paint. Because oil-based paint has naturally aged and lost its flexibility, resulting in fissures produced by temperature changes.
Possible Root Causes (Checking)
Several layers of earlier oil-based paint aged naturally. The paint has to move when the painted substance (typically wood) contracts and expands over time, and it “checks” as it loses elasticity.
Repair and Maintenance
Remove the old paint, sand, prime, and repaint with a latex-based paint that is flexible. Make use of high-quality latex paint.
This article should help you identify and repair external paint problems that are present. Check out more well-known exterior paint problems and solutions in article 2.