Exterior Problem Solver
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Patterned cracking in the surface of the paint film resembling the regular scales of an alligator.
- Application of an extremely hard, rigid coating, like an alkyd enamel, over a more flexible coating, like a latex primer.
- Application of a top coat before the undercoat is dry.
Natural aging of oil-based paints as temperatures fluctuate. The constant expansion and contraction results in a loss of paint film elasticity.
- Old paint should be completely removed by scraping and sanding the surface; a heat gun can be used to speed work on large surfaces, but take care to avoid igniting paint or substrate. The surface should be primed with high quality latex or oil-based primer, then painted with a top quality exterior latex paint.
Formation of fine powder on the surface of the paint film during weathering which can cause color fading. Although some degree of chalking is a normal, desirable way for a paint film to wear, excessive film erosion can result from heavy chalking.
- Use of a low-grade, highly pigmented paint.
- Use of an interior paint for an outdoor application.
- First, remove as much of the chalk residue as possible, scrubbing with a stiff bristle brush (or wire brush on masonry) and then rinse thoroughly; or use power washing equipment. Check for any remaining chalk by running a hand over the surface after it dries. If noticeable chalk is still present, apply a quality oil-based or acrylic latex primer (or comparable sealer for masonry), then repaint with a quality exterior coating; if little or no chalk remains and the old paint is sound, no priming is necessary.
The splitting of a dry paint film through at least one coat, which will lead to complete failure of the paint. Early on, the problem appears as hairline cracks; later, flaking of paint chips occurs.
- Use of a lower quality that has inadequate adhesion and flexibility.
- Overthinning the paint or spreading it too thin.Poor surface preparation, especially when the paint is applied to bare wood without priming.
- Painting under cool or windy conditions that make latex paint dry too fast.
- It may be possible to correct cracking that does not go down to the substrate by removing the loose or flaking paint with a scraper or wire brush, sanding to feather the edges, priming any bare spots and repainting.
- If the cracking goes down to the substrate remove all of the paint by scraping, sanding and/or use of a heat gun; then prime and repaint with a quality exterior latex paint.
Reddish-brown stains and spots on the paint surface.
- Non-galvanized iron nails have begun to rust, causing bleed-through to the top coat.
- Non-galvanized iron nails have not been countersunk and filled over.
- Galvanized nailheads have begun to rust after sanding or excessive weathering.
When painting new exterior construction where non-galvanized nails have been used, it is advisable to first countersink the nailheads, then caulk them with a top quality, waterbased all-acrylic or siliconized acrylic caulk. Each nailhead area should be spot primed, then painted with a quality latex coating. When repainting exteriors where nailhead rusting has occurred, wash off rust stains, sand the nailheads, then follow the same surface preparation procedures as for new construction.
Loss of paint due to poor adhesion. Where there is a primer and top coat, or multiple coats of paint, peeling may involve some or all coats.
- Seepage of moisture through uncaulked joints, worn caulk or leaks in roof or walls.
- Excess moisture escaping through the exterior walls (more likely if paint is oil-based).
- Inadequate surface preparation.
- Use of lower quality paint.
- Applying an oil-based paint over a wet surface.
- Earlier blistering of paint (see Blistering).
- Try to identify and eliminate souce of moisture. Prepare surface by removing all loose paint with scraper or stiff wire brush, sand rough edges, and apply appropriate primer. Repaint with a top quality acrylic latex exterior paint for best adhesion and water resistance.
Concentration of water-soluble ingredients on latex paint, creating a blotchy, sometimes glossy appearance, often with a tan or brownish cast. More likely with tinted paints than with white or factory-colored paints.
- Painting in cool, humid conditions or just before they occur. The longer drying time allows the paint’s water-soluble ingredients – which would normally evaporate, or be leached out by rain or dew – to rise to the surface before paint thoroughly dries.
- Mist, dew or other moisture drying on the painted surface shortly after it has dried.
- Avoid painting in the late afternoon if cool, damp conditions are expected in the evening or overnight. If the problem occurs in the first day or so after the paint is applied, the water-soluble material can sometimes be rinsed off rather easily. Fortunately, even more stubborn cases will generally weather off in a month or so. Sufactant leaching should not affect the ultimate durability of the coating.
Painting the exterior of your home will do more than simply create an attractive appearance. It will provide protection from the sun, the weather, and other environmental factors that can gradually damage your home.
Many homeowners are becoming do-it-yourselfers and choosing to repaint their own homes — a move that can save them money. If they plan carefully, the results can be entirely satisfactory. Important considerations are: choosing attractive colors; choosing correct types of paint; selecting proper applicators; preparing the surface well; following correct application procedures; and thoroughly cleaning up.
Exterior color selection
Whether you’re repainting or painting your home for the first time, you’ll want to carefully select exterior colors. After all, the outside of your home will likely be in public view for all the world to see!
Here are some points to remember when making your selection:
- Consider neighboring homes — you’ll want yours to be compatible with those surrounding it.
- Some parts of the house may not be painted — for instance brick or roofing material therefore the color of those materials must be considered.
- The part of the country you live in might sway your color decision. For example, colorful Victorians are fashionable in San Francisco, but would seem out of place in some other areas of the country.
- You can’t go wrong by painting the body of the house a light color and the trim in a darker color. Simply choose an attractive combination such as a creamy beige body with chocolate brown trim, or a light grey with slate blue trim.
- On homes with interesting architectural details, use an additional color to emphasize them.
- For inspiration, look at actual homes or photographs of them in magazines. You’ll notice many that you dislike, but you’re sure to find others that suit your taste.
Paint type selection
There are several varieties of paints available today for exterior painting — many suited especially for a particular surface. It is not practical to list all these paints, but this information will affirm you with some helpful facts to take with you to your paint store. Paints are designed to be used on certain surfaces and to perform well under certain conditions. You should consider the various surfaces of your home that will need painting and choose the paints with this in mind. The paint retailer can be helpful and reading the paint can labels can also be beneficial.
Most paints are either solvent-thinned or water-thinned and often you can have a choice of either type for a particular surface. Alkyd and oil-based paints are solvent-thinned. They are durable, and resist abrasion well. Because they are solvent-thinned, clean-up of brushes, rollers, etc. must be done with turpentine or mineral spirits.
Latex paints are water-thinned. They are often more popular because brushes, rollers and splatters can usually be cleaned up with soap and water. Latex paints are durable, easy to apply, and retain their color well.
Either latex or alkyd types can be used successfully provided the surface is properly prepared. Both are available in a variety of sheens from flat to glossy — the lustre or sheen of a product is referred to as its gloss. A paint with a higher gloss is preferable on exterior areas where dirt or abrasion are a problem — such as doors and trimwork. For high gloss trim paints, alkyds are usually preferred. Flat paints are attractive and are often preferred on siding, masonry and stucco.
Most wood surfaces may be topcoated with any of the exterior paints — latex, alkyd, or oil-based.
Exterior wood stains, available in solid or semi-transparent types, are popular for textured wood surfaces. Solid stains hide the color of the wood, but at the same time allow the texture of the wood to show through. Semi- transparent stains are used when more of the natural wood color is desired.
Coating exterior wood surfaces with clear coatings is a somewhat questionable practice. Sunlight penetrates the clear coating, affecting the wood surface. This causes the clear coating to lose adhesion and peel off. If you decide to use a clear finish, it is necessary to set up a strict regular maintenance program. A new clear coating should be applied before deterioration of the old coating begins. Some clear coatings contain ultra-violet absorbers which help to lengthen their life. Ask your paint retailer for a recommendation.
Considerations for specific surfaces:
Masonry — masonry often contains alkali, therefore a paint which is not affected by alkali should be used. Latex paints are the usual choice for masonry, but buy one which is designed for use on masonry.
Siding above decorative masonry surfaces — since chalk will wash down and discolor lower surfaces, freely chalking flat white paints should not be chosen for these areas.
Asphalt roofs — no primer is required. Clean all dirt off and use special asphalt roof coatings, many of which have metallic aluminum pigment for heat reflection and durability.
Wood shingles/shakes — painting is usually not recommended for wood roofs. Because of moisture problems it is difficult to keep paint intact on rough wood surfaces. However, a water-repellent preservative will give the wood some protection against decay, stain, fungus, swelling, shrinking and warping.
Porches and decks — should be coated with special porch and deck paints or stains, designed to stand the wear and weather.
Rough sawn siding — use a solid or semi-transparent stain.
Metal surfaces — once primed properly with a corrosion-resistant primer, they can be topcoated with any exterior paint.
There are many miscellaneous surface areas such as swimming pools, underground metal, driveways, and glass windows for which specific coatings are available. Ask your paint retailer for a recommendation.
On surfaces that have never been painted, or areas that have become bare, the first coat should always be a prime coat. The primer seals porous surface materials so the topcoat won’t soak in and dry unevenly. It also forms a tight bond between the topcoat and underlying surface material.
The keys to selecting a primer are adhesion to the surface and compatibility with the topcoat. The paint you select for a topcoat will usually recommend a type of primer on the label.
Figuring the proper amount of paint to buy
It is always helpful to buy all the paint you will need for a particular job at one time — both for convenience and to reduce the chance of a slight color variation between batches. Often your paint retailer can select all your cans of paint from the same batch.
The amount of paint needed will depend on the type of paint, kind of surface to be painted, and the amount of surface area to be covered. To compute the surface area, measure the height and width of each area and multiply to find the number of square feet of surface .
The paint can label will tell you the number of square feet that a gallon of the paint will cover. Divide that into the number of square feet to obtain the number of gallons per coat to buy. It is important to apply the paint at the spreading rate recommended on the label by the manufacturer.
The type of surface you are painting can also make a difference. For instance, rough materials have substantially more surface area than smooth materials, so more paint will be required on them.
Selecting the best applicator for the job
The right paint applicator can mean the difference between a long-lasting, professional-looking paint job and a sloppy, amateur one. Perhaps more importantly for the do-it-yourselfer, the proper applicator will make the job much easier.
For most exterior painting jobs, three sizes of brushes are needed: 1 to 3 inch oval or sash brushes to paint window frames and moldings; 2 to 3-inch brushes for shutters, windows and door trim; and 3 to 4 inch brushes for larger areas.
You might choose to use a roller — a 7 to 9 inch roller can be speedier over large flat surfaces. However, a roller should not be used for the primer coat on wood because brushing gives better penetration and more complete coverage.
Pad applicators are good for smooth surfaces since they are usually faster to use than a brush, but be sure to apply enough paint for protection.
Brushes are available in a variety of bristle materials; rollers come in various nap lengths and fabrics; and pad applicators also vary in fabric types. The applicator wrapper covering should tell you what type of paint that particular applicator is intended for. The key is to select a good quality applicator — the extra money you might pay will be well worth the results.
Proper surface preparation is the key
It has often been said that the actual painting is a breeze — the surface preparation is what takes the most time and effort. Proper surface preparation, however, is essential to a successful paint job. A poorly prepared surface is often the cause of later paint problems. But regardless of that, it is always worth the time spent preparing a surface, because the results will be more attractive and longer-lasting.
The first step should be a thorough inspection of your home’s exterior, checking for peeling paint, dirt, grease, cracks, knots, rusty nail heads, bare areas and mildew. Follow these steps to obtain the smooth, clean, dry surface before painting:
- Scrape all surfaces clean of peeling paint and rust.
- Remove oil, grease and dirty by washing with a detergent or commercial cleaner recommended for washing paint. On siding, remove dirt and chalk with a solution of the above type detergent and a sponge, brush, or pressure washer. (Paints often chalk slightly to prevent dirt collection. Latex paints are sensitive to heavily chalked surfaces.)
- Remove all traces of mildew with a stiff brush and a commercial surface cleaner recommended for removing mildew. Or, mix one quart of household bleach with three quarts warm water. Rinse well with clean water before painting.
- Cracks in siding or open joints between building materials should be caulked. Prime unpainted surfaces before caulking.
- If siding has wood knots that contain resinous material, use turpentine or mineral spirits to remove resin, then seal with a special knot sealer available at your paint store.
- On iron and steel, rust should be sanded or wire brushed away.
- Fill particularly rough, unpainted masonry surfaces with masonry block filler — a thick material that creates a smoother, less porous surface.
- Glossy painted surfaces should be roughened with sandpaper — particularly important under eaves or overhangs. These areas must also be washed with detergent and water to remove soluble salts which have collected.
- Sand rusty nailheads, then sink them slightly below the surface with a hammer and nail punch. Apply corrosion-resistant primer over the nailhead and add putty if necessary. Then sand smooth.
- Spot prime bare areas. Even if siding is factory primed, spot priming will be necessary on bare or rusted areas. Minor scratches, dents and raw edges should be feather sanded and spot primed.
Here are some additional suggestions for special surfaces:
- Plywood is particularly susceptible to moisture absorption through the edges of the plywood sheets; therefore it is necessary to seal the plywood, particularly the end grain edges (short sides). Edges that will be exposed as well as edges that will be covered after construction should be sealed. This is also true of the edges of solid wood.
- Outdoor metal surface preparation is extremely important. First, remove all rust, dirt and grease. Any flaking paint should be removed and the surface should then be sanded. The entire surface should then be primed with a corrosion-resistant primer.
- Aluminum siding, after years of exposure, has usually collected a deposit of dirt and chalk that must be removed before repainting. This is usually easy to wash off with detergent and water.
Application of the exterior paint
Tips for a successful outdoor painting job:
- Choose a time of day when morning dew is gone and when sunlight is not direct — if paint dries too fast, lap marks will show.
- New wood should be painted as soon as possible after installation to prevent deterioration of the surface.
- When using latex paints the temperature should be above 50 degrees F. But, if the temperature is above 70 degrees, it is best to paint in shaded areas, following the sun around the house so that paint won’t dry too quickly and leave lap marks.
- Two topcoats are recommended to prolong the life of the coating — the first should be applied with a brush, rather than a roller or pad, to make sure an adequate film of paint is worked into the surface.
- After thoroughly mixing, split full gallons of paint between two containers — it will be safer and easier to use.
- The bottom of your ladder should be about one-fourth the total working length of the ladder away from the base of the support wall .Never climb above the third rung from the top. Use stepladders to reach lower areas such as the tops of windows and door frames.
- Load your brush properly — dip the bristles to half their length and remove excess paint by tapping (not wiping) the brush against the side of the container.
- For siding, start at an upper corner and paint a deer strip, extending it horizontally to the next corner or to an intervening door or window. Next, starting below the first strip of paint, begin painting a new one, overlapping the dry area with the previously painted area .At the end of the day, stop work at a natural boundary to prevent lap marks.
- After the main body of the house has been painted, the next step is to paint wood trim and frames around windows and doors. Use a thin piece of metal or cardboard as a shield or buy a special paint shield at a paint store. Wipe the shield frequently to prevent paint buildup.
- When using a roller, be sure to use a tray especially made for roller use.
- If possible, shutters should be removed before painting, and then painted on both sides.
- Protect window glass with a special plastic tape used for painting stripes on cars. Available at auto supply stores, it won’t allow paint seepage underneath.
Clean-up at the end of the day
Clean-up after painting need not be a chore if you follow these few suggestions:
- Clean up spills promptly as they occur — before paint dries.
- Clean all paint applicators, clothes, and skin before the paint has had a chance to dry.
- Follow cleaning instructions for the particular product you use (found on the can label).
How should I prep old aluminum siding before painting? What type of primer is the best for siding?
Remove as much “chalk”, dirt and mildew as you can. This is done by power washing or by scrubbing and rinsing. The only times a primer would be needed are:
1) if any bare aluminum is exposed; then use a latex corrosion-inhibitive primer;
2) if there is still much “chalk” left on the surface, apply a quality exterior alkyd (“oil-based”) primer recommended for aluminum siding by the manufacturer. (“Chalk” is powdery pigment on the surfaced of the weathered siding, that comes off when you rub the palm of your hand over the surface.)
After removing the old chalky white from aluminum siding, I was told to wipe the siding with mineral spirits before priming it. Is this a necessary step before washing it? I had to use a sander to remove the road salt and the siding was badly pitted.
No, unless you have some oily contaminant such as road tar on the siding, do not use mineral spirits. The road salt that you removed was probably white aluminum corrosion (aluminum oxide). After you clean and rinse the surface, you will need to prime all areas of exposed aluminum (that is, where you can see the metal), or where any of the white salts were.
For the primer, use a latex corrosion-inhibitive primer. Ask for this at a paint store. You may find it just as easy to prime all of the siding, rather than just the areas mentioned. If you do prime everything, you will get a more uniform appearance from the paint, compared with if you only prime some parts. For the paint itself, use a top of the line 100% acrylic latex house paint in a flat finish.
What type of paint should I use to paint aluminum siding?
In general, use a top of the line exterior 100% acrylic house and trim paint in a flat or satin finish. This assumes proper surface preparation, including removal of dirt, chalk and mildew. Unless metal is exposed, no primer is needed. If bare metal is visible, remove any white oxide with a non-metallic scouring pad such as ScotchBrite, then wash off and rinse, then apply a latex exterior corrosion inhibitive primer to the exposed metal area. As for the paint, use a flat if the siding is at all uneven and/or dented (while the satin finish will provide a rich, fresh appearance, it will accentuate the dents.
I read from your site that exterior painting should be done when it’s over 60°F. How long after application does this guideline apply….For example, the forecast calls of daytime temperatures in the mid-60?s but overnight temperatures in the low 40?s—Is that a “go” or a “no go”?
The 60°F guideline is ideal. The minimum application temperature on the label should be followed carefully. This typically is 50°F. for latex paints. We suggest these points:
1. Do not apply the paint if the air temp. is below the recommended minimum, or is predicted to drop below the minimum for the next 36 hours.
2. Do not apply the paint if the surface is below the minimum recommended temperature. For example, if the temperature in the night was 35°F, and the air temperature is now up to the minimum recommended temp of 50°F at 9:00 am, and you are painting aluminum siding, the siding itself is probably too cold.
Not following these guidelines can cut years off the life of the paint job, before cracking and loss of adhesion set in. Oil based paints are more forgiving than latex in this regard, but lower temperatures will still retard their dry, which can result in dirt collection, especially if it gets windy.
Here is our summary statement on this: The extremes in temperature and sunshine should be taken into account when applying primers, paints and stains. Care must be taken that they can form a good film. This means they should not be applied at a temperature lower than the recommended minimum temperature for the product (typically, 50 degrees F.)… this includes temperature of the surface being painted; and application should not be done if the temperature is predicted to be below the recommended minimum anytime in the next 36 hours. Also, don’t apply paints under conditions that will make them dry very quickly: do not paint in direct sunshine, and in warm, dry, breezy conditions.
I have several contractors quoting on painting the exterior of my home. However, when questioned on what is the best method to apply the paint (hand brush or sprayer), they are as many opinions as there are contractors. My home is located in Raleigh, NC and the exterior siding is hardboard.
Basically, both spraying and brushing are fine, so long as the paint is put on at the proper spread rate (sq. ft./gallon). Spraying will provide a smoother appearance, and less chance for mildew to get into brush marks and grow. With spraying, the painter has to be careful about getting a full coat onto areas that are next to areas that won’t be painted, so careful masking must be done. Some people think sprayed paint will not adhere as well as if brushed, but we have not seen that, so long as the surface has been properly prepared.