Exterior Paint 101
Painting the exterior of your home is a big undertaking: you'll need the right type of paint, quality tools and few tips to get the job done.
Painting the exterior of your home is a big undertaking: you’ll need the right type of paint, quality tools and some guidelines on getting the job done.
With exterior painting, be sure to take into account the fixed colors of your home: brick, stonework, and the roof color, for example. The most flattering color treatments will be those that work well with these existing elements. Consider choosing a color that will pick up the color of a non-painted area—the brown that appears in your brick or a green highlight from your stonework, for example.
Also, remember that no home exists in isolation: Its appearance is affected by the appearance of neighboring homes and even the color of shrubs and trees around it. You probably don’t want to paint your home the same color as your next-door neighbor’s, but you probably do want to select a hue that will look attractive alongside it. Furthermore, be aware of the fact that certain colors look more at home in certain surroundings. For example, earth tones are always a good choice in natural, wooded areas, but they may not be the best choice in other settings.
Another factor to consider is the architectural style of your home. Oftentimes, a home looks most attractive when painted in period colors. Formal Colonial or Greek Revival homes look great with white exteriors and muted interiors, while Victorians come to life with bold color treatments that accentuate ginger bread and other interesting architectural details.
Similarly, the safest approach to exterior painting is to use white, beige, or another neutral color on the siding and a darker accent color on the trim. Dark brown is often a good general-purpose color for exterior trim.
Extreme heat or cold, moisture, and prolonged exposure to the sun all take their toll on the exterior of our homes. When paint deteriorates, cracks in the substrate are exposed and let damaging moisture penetrate the home. A good paint keeps severe weather on the outside but breathes to allow damaging moisture vapor to escape from the inside.
These days just about every paint company offers their version of a weatherproof coating. Elastomeric coatings that retain their flexibility and stretchability over a wide range of temperatures are becoming popular solutions for homes in storm or extreme-weather regions. The applicability to a host of surfaces adds to these products’ appeal.
There are two general categories of paintbrush: those made of natural-hair bristles and those made with synthetic materials, such as nylon or polyester. If you are working with alkyd or oil-based paints and coatings, you can use either natural bristle brushes or synthetic bristle brushes. However, high-quality natural bristle brushes work best when applying enamels or any topcoat. When applying any type of latex coating, use only brushes with synthetic bristles. No matter how much water they are exposed to, they hold their shape and maintain proper stiffness. Top quality polyester brushes are well worth the initial cost. When properly cleaned and stored, they will continue to apply paint smoothly and uniformly for years to come.
For large exterior surfaces, use a 4″-wide (100mm) flat brush with a thickness of 3/4″ to 1″ (25mm to 3mm). For precise painting of window frames and trim, use angled sash brushes between 1″ (30mm) and 2 1/2″ (60mm) wide.
Another option for your exterior paint job is using a paint sprayer. For quick coverage of large surface areas, it is tough to beat power-spraying equipment. While sprayers may use more paint than other types of applicators, the ease and convenience they offer make them ideal for large jobs.
Temperature Blisters. Paint bubbles can show up pretty quickly, from within a few hours to a few days after application. The blisters are only in the top coat of paint and appear most often in oil-based paint. A quick rise in temperature, like sunlight shining directly on the newly painted wood, causes a thin skin to form on the outer surface of the paint. The skin traps inner wet paint that produces vapor when it heats up. The vapor expands and causes the paint to blister from underneath.
To repair blisters, scrape them off, smooth the edges, and repaint, being sure to avoid direct sunlight while the coat dries. Experts suggest establishing a painting order that follows the sun around the project. Thick coats and dark colors are more likely to blister than light colors and thinner paint.
Moisture Blisters and Peeling. Moisture causes problems for paint. Rain, dew, ice, and snow on the outside or vapor and moisture buildup from the inside can cause problems with exterior paint. When moisture penetrates the paint, blisters can form and paint can peel. Moisture blisters, unlike temperature blisters, go through all coats of paint down to the wood.
To stop moisture blisters, you must locate the source of the moisture and repair it. Improper construction techniques and lack of flashing can cause outside water to pool at joints, on window sills, frames, or on the end grain of the wood.
Water vapor moving through walls to the outside paint can come from plumbing leaks, sink or tub overflows, cooking, or using a humidifier. The vapor moves through exterior walls if there is not a vapor barrier or if the barrier is incorrectly installed. Look for this deterioration particularly outside bathrooms, laundry rooms, kitchens, and the gable ends of the attic.
Intercoat Peeling. Another type of peeling occurs when a newer coat of paint separates from the coat underneath. An inadequately prepared or dirty surface is one cause for a weak bond. Another is that the two paint layers are incompatible. For example, an oil-based paint may have been applied over a latex-based paint. They are incompatible and can peel away from one another.
Peeling can also occur when too much time has elapsed between applications of the primer coat and the top coat. If more than two weeks separates the primer application and the paint coat, the primer’s surface can begin to break down and prevent proper bonding with the paint. To correct the problem, you must remove the paint and properly clean the surface.
Cross-Grain Cracking or Crazing. Too many layers of paint or one layer that is too thick can result in an interconnected, uneven pattern of cracks. The thick paint is unable to expand and contract with the wood, so breaks result, starting in the outer layers. If the problem is not corrected, moisture enters the paint layers, causing deeper cracking and deterioration.
Surface cracking may require sanding and repainting. Deeper cracks will require a complete removal of the old paint. Once the wood is bare, clean it and treat it with a paintable, water-repellant preservative. Once the preservative has dried, apply a primer and top coat at the recommended spread rates.
Chalking. Some exterior paint has a powdery coating. Chalking comes from the disintegration of the paint resin due to exposure to the sun’s ultraviolet rays. This gradual deterioration is how paint is supposed to age. Too much, however, can cause discoloration of other painted areas below as rain washes off the chalk. It also signals that the paint is rapidly deteriorating.
Chalking was more of a problem with older paints that contained excessive pigment for the amount of binder, but other triggers include the failure to properly prime and seal exterior wood, spreading the paint too thinly, or thinning the paint too much. To correct excessive chalking, the surface must be cleaned and repainted.
Staining. A stain is typically caused by moisture. The most common source is rusting metal nails or anchoring devices in the wood. The second cause is a chemical reaction between moisture and wood, such as red cedar, which results in color buildup on the surface.
Rusty nails can be hand sanded and coated with a rust inhibitor and finish coat. Unless the wood is too fragile or the exposure of the nail head is related to the original construction system, it’s best for nail heads to be countersunk, primed, and filled before painting. Stains from wood extracts need to be cleaned, rinsed, dried, and primed with a stain-blocking primer before applying the finish coat. Check with a knowledgeable local paint retailer for the best cleaning mixture.