Make your Exterior Painting Job Last
Everyone wants their exterior painting job last as long as possible right? Once someone asked me. I would like to have my home painted again, and this time I want it done right. I’m striving for that crisp, clean look, and I want it to last. A neighbor had his house done and five years later it still looks great. I painted three years ago and my house looks lousy. Why is that?
The answer is “Preparation”. This single word unlocks the mystery of why paint jobs that are done by professional last longer than those done by a homeowners. What many homeowners don’t know is that preparation is 80 percent of the work in any paint job.
Essentially, there are six key steps.
1. Fix indoor moisture problems that lead to outdoor paint problems.
Repair roof leaks and soggy basements. Vent kitchens and baths to the outside. Moisture enters a house as liquid, but it leaves as vapor that lifts exterior paint when it exits the wall outside poorly vented rooms.
2. Repair damaged surfaces.
Don’t paint over wood affected by rot or insects, or gouged by careless ladder placement. Replace all damaged wood or repair it. Dig out rusty fasteners. Water running over a rust blister transfers the oxides to the paint, staining it.
3. Clean siding and trim.
Dirt is slippery, and paint won’t stick to it; you must remove all dirt, mildew, cobwebs and greasy gunk in order to have a clean surface to work with. Don’t tackle everything in one cleaning. Instead, proceed in two stages. First, use a garden sprayer to apply a mildew-killing solution of Jomax (a bleach activator), bleach and water. Next, remove weathered paint and greasy dirt using siding cleaner, which is sold at paint stores and home centers. Professional painters are divided on the benefits of power washing for this step. Some believe that hand scrubbing and using a garden hose and nozzle is better. If you decide to power wash, go easy. Don’t damage the siding and trim.
Regardless of the cleaning method, rinse thoroughly and gently to remove cleaner residue, which is typically alkaline. Left behind, this residue can loosen paint applied over it.
4. Scrape and sand.
Remove damaged paint, and then use sandpaper to feather the rough edges left behind. Otherwise, the sharp edges will create thin, weak areas in the new paint. Brush away any dust created and rinse the siding and trim gently but thoroughly.
5. Prime if necessary.
Primer is to the topcoat what the foundation is to your house. Areas scraped to bare wood need a layer of primer, as do spots that have hairline cracks but are otherwise sound. Prime the entire house if it needed extensive scraping.
The great alkyd-versus-latex-primer debate marches on, even to this day. Many pros still prefer an alkyd (oil base) primer when the siding and trim are covered with a layer of dusty paint particles known as chalk—despite washing. Sure, it’s a pain to clean your brushes of the stuff (use mineral spirits), but alkyd primers, where available, penetrate and bond tenaciously to damaged or weather-beaten surfaces.
6. Apply paint correctly.
Paint needs to be applied at the right thickness, about 4 to 5 mils (0.004 to 0.005 in.) when wet—or the thickness of a sheet of copier paper. Too thin, and the dried paint will be weak. Too thick, and it will sag and crack. You can check the paint’s wet thickness with a device called a wet-film thickness gauge. To be honest, only pros use these, and often it’s just to check that their helpers are not spreading the paint too thin. If you’re in doubt about your paint application, get one. These are generally quite expensive; you can find affordable models at dynesonline.com.
Finally, don’t apply paint in strong direct sunlight or high wind, which can make the water or petroleum solvents evaporate out of the paint too quickly. This does two things. It can reduce the paint’s ability to flow out and level as it should. It can also weaken the bond the paint molecules make with each other and with the substrate.