Login or Register to download the PDF version of this article. (232.11 kB)
Here’s a plausible scenario: You’ve just completed a new custom home — the clients are ecstatic, the project looks great. With fresh paint on the outside, the house’s curb appeal promises to bring new client referrals. Then, within six months or a year, the phone call comes: "The paint is peeling; can you do something?" Premature paint failure on wood siding has become commonplace in recent years. The reasons cited are varied. Some blame paint quality, claiming that paints are not as durable since the lead content was banned. Others point to the declining quality of the wood siding itself. Still others argue that the high interior moisture levels in today’s tight houses cause water vapor to move through the exterior walls into the back of the siding, which eventually causes the paint to peel and blister. All of these arguments have some merit. There is often a complex combination of causes behind a particular paint failure. But paint failure is not inevitable: In most cases, if the job had been designed and executed properly in the first place, the failure could have been prevented. Success with painted siding starts with an understanding of how the siding you choose will perform under local weather conditions. Next, it’s necessary to match the finish to the siding — a given finish performs differently on different types of siding. In this article, I’ll look mainly at two areas: 1) the properties of wood that most affect paint durability; and 2) varieties of paints, stains, and other finishes, and how they perform on various types of siding. Although it’s not covered here, ventilation details are critical to good paint performance. This includes proper roof venting as well as using adequate indoor exhaust ventilation to remove excess moisture from the building. When the budget allows, vented siding, where an air space is created between the sheathing and siding, is unquestionably one of the best details for ensuring long-term paint performance (see "Rain Screen Siding Retrofit," 4/98).
How wood siding performs varies not only from one wood species to another but within the same species. These natural variables, and the variables created during the manufacturing processes, have important influences on wood’s finishing properties and its durability.