Choosing the Right Exterior Paint
One difference between exterior alkyd and latex paints is how they cure. Alkyd paints usually are dry to the touch in 4 to 6 hours and can be recoated in 8 to 12 hours. They continue to harden several months after application, providing an excellent barrier to moisture. Latex paint usually is dry to the touch in 30 minutes and, in warm, dry weather, is resistant to light showers or dew after about 4 hours.
Whether you choose alkyd or latex,
flat paint is best on siding for resisting moisture, and
semigloss or gloss types are best for trim and doors because of
their durability.
Alkyd Paints
Alkyd paints are available in enamel and so-called house
paint. Enamel paint is typically found in a range of ready-to-mix
colors suitable for general use and is a particularly good choice
for trim. Alkyd enamel dries to a hard and nonporous finish.
Alkyd house paint is more flexible than enamel, but it is not
available in some states because of air-quality regulations. In
other states, it is available only in quart cans, making it
expensive to use as a coating for exterior siding.
Alkyd paints tend to adhere better than latex to problematic and
glossy surfaces. Because they dry more slowly than latex, alkyds
give brush and roller marks more time to flow out, leaving a
smoother finish on the surface.
Latex Paints
The best exterior latex paint is made with all-acrylic resin.
Lower-quality varieties are made with vinyl acrylic and other
additives. While all-acrylic paints are more expensive, they
offer better adhesion, gloss, and color retention than acrylic
mixtures.
The water-base formulation of
latex paints also makes them easier to clean up, less expensive,
and faster drying than alkyds. In addition, latex paint dries to
a porous finish, allowing moisture in wood to evaporate through
the paint film, which prevents peeling.
Stains
Stains come in transparent, semitransparent, and solid-hide
formulations. Solid-hide stains, the most durable and protective
type available, are essentially wood-toned paints.
Semitransparent stains are the right choice for areas where you
want to show the natural grain of the wood. Transparent
formulations are used where you want to display the wood’s
natural beauty while offering a degree of weather protection.
When Do You Need A
Primer?
You need a primer when the surface to
be painted is porous or the paints are incompatible (such as when
you apply latex paint over alkyd).
An existing painted surface in good condition and compatible with the finish coat may not need an additional primer.