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Choosing Exterior Paint

House paints made to cover siding and exterior trim tend to be more durable and more expensive than interior paint. That’s because exterior paints contain additional resins and other ingredients that make them last longer and resist moisture. Also many have a larger amount of pigmenting, which gives them a deeper, more vivid color. Like interior paint, exterior paint conies in two basic varieties: water-thinned (latex) and solvent-thinned (oil- or alkyd-based). Those with oil and alkyd bases dry slowly, making them susceptible during application to being marred by insects and sudden rainstorms. Once they set up, they develop a hard surface that is resistant to water. However, unless the surface is very well prepared, they are prone to flaking.

Properly applied, modern latex exterior paint (though not porch and deck paint) is more durable than solvent-based paint. Latex paints are easier to work with, dry quickly, and have a porous, “breathing” quality that makes them less likely to flake. They will likely peel, however, if applied over an improperly prepared oil-or alkyd-based finish. Chalking-type latex paints shed dirt by gradually eroding with each rainfall. Usually you can see the “chalk” on foundation walls, shrubbery, and your coat sleeve if you brush against a painted surface. Newer formulations achieve durability without this chalking feature.

Latex paints tend to show brush marks, while solvent-based paints “level” to a more even surface. If a surface will be often handled or walked on (as is the case with a porch), solvent-based paint provides a more durable surface. Do not use latex paint over a surface covered with solvent-based paint, unless you first apply a primer or thoroughly sand the surface. To find out which type of paint is present, remove a flake or chip and see whether it is flexible. Latex paint will bend slightly before cracking; a flake of solvent-based paint will snap readily. If you bring in a chip, a paint dealer can tell you for sure. If you’re not certain what type of paint was used before, it’s safest to apply a solvent-thinned paint.

Most people prefer a flat, eggshell, or satin finish for large exterior expanses. Reserve semigloss and gloss for areas subject to hard use or for trim. What about one-coat house paints? If you plan to match or approximate the present color, any paint will cover in one coat. However, products sold with a one-coat guarantee are thicker, with more resins and pigments. Most guarantees specify that the paint must be applied over sound existing surfaces or primed new wood. You will pay more for a one-coat paint, but the extra money spent might pay off handsomely, especially in terms of time saved. The chart will help you sort through the often-confusing array of products found in paint stores. As a general rule, the more expensive the paint, the more durable it will be.

Estimating Paint Needs

How much paint you need depends upon the type and condition of the surfaces that you’ll be covering, the method of application, and the paint itself. Conditions vary considerably, so read the manufacturer’s coverage figures, then buy a little more than you need. If your home has narrow lap siding, add another 10 percent to your estimate. For textured materials, such as shingles or shakes, add 20 percent. Masonry and stucco—both porous surfaces that soak up lots of paint—can take up to 50 percent more.

To compute surface area, measure from the foundation to the eaves and multiply by the distance around the house. For each gable end, measure the distance from eaves to the peak, measure the width of the wall, and multiply the two. Then divide the result by two. If you buy paint of a standard color, most stores will let you return unopened cans. Check with your retailer about return policies for custom mixed paint.

Comparing Exterior Paints

Type

Characteristics/Uses

Application

Vinyl latex

Easy cleanup, durability, and fast drying make latex the choice for amateurs. It can be applied over damp surfaces. Latex is naturally mildew-proof but is incompatible with a previous solvent-based finish.

Don’t thin latex. Apply with one stroke of the brush or roller; if you work it out too far, you’ll get thin spots.

Acrylic latex

The highest-quality latex paints contain 100 percent acrylic resins; vinyl resins are not as durable. It dries faster than most and will cover just about any building material, including masonry and properly primed metal.

Application technique is about the same as vinyl latex paint.

Alkyd

Alkyd, the most common type of solvent-thinned paint, has most of the same properties as oil-based types, but dries more rapidly; good over old oil- or alkyd-based coatings; excellent hiding power.

Thicker consistency makes alkyd more tiring to apply, but it levels smoother than latex.

Oil

Slow drying times (12 to 48 hours), strong odors, and messy cleanup make oil a less popular choice for amateurs, though some pros swear by its durability.

Drying time makes marring by bugs and rain real perils.

Primers

Use a recommended primer to seal new wood or metal, to kill stains, or prior to applying latex paint over existing solvent-based paint. Alcohol-based primer is the most effective, but solvent and latex types also work.

Priming usually is easier than finishing, but porous surfaces can soak up a lot of primer.

Stains

Solvent- or latex-type stains provide transparent, semitransparent, or opaque finishes for natural wood siding and trim; some include preservatives or offer a weathered look.

Brush, roll, or spray on almost any way you prefer.

Porch and deck

Alkyd and polyurethane types are the most durable because they produce a hard, washable surface. Some types are formulated for concrete floors. Surface preparation varies; colors are limited.

With most types, you just pour the paint on the floor, then work it outward with a long-handled roller or applicator.

Metal

Solvent- or water-thinned types include rust-resisting priming ingredients so you needn’t worry about small bare spots. All-bare metal should be primed separately. Rusty-metal primer seals a rusty spot.

Brush, roll, or spray on for a broad range of finish effects.

Marine

Formulated especially for boats, marine paint provides a super-durable finish on wood and some metal trim. It’s expensive, so it’s generally inappropriate for large areas.

A gooey consistency makes it difficult to apply.

Masonry

This category includes latex, epoxy, Portland cement, rubber, and alkyd. Some serve as their own primers. Seal masonry with clear silicone.

Latex is easy to apply; other types can be a lot of work.

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