How to Paint Your House (and why you may not want to paint your barn)

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If you opt to go with paint or traditional wood stain, preparation will greatly extend the life of the coating. And getting rid of something called “mill glaze” is the reason why. The rapid rotation of planer knives that transforms rough lumber into smooth boards at the sawmill leaves behind a legacy of burnished fibers and heat-sealed surface resins that prevent finishing liquids from penetrating deeply enough to gain a durable foothold. Mill glaze is a universal condition on all new smooth wood and it causes more premature finish failure than anything else. Paint needs to sink into open wood pores to deliver maximum working life, and a lot of research has gone into determining exactly how to make this happen.

During a five year field study, the world’s largest coatings manufacturer, Akzo Nobel, conducted field trials across North America to determine which pre-application technique best maximized the absorbency of wood surfaces. Chemical wood wash products and mill glaze removers were compared side-by-side with pressure washing regimes using plain water and cleaning agents. The results of sanding were analyzed, too. As it turned out, surfaces prepared with a 60-grit abrasive yielded the best absorbency and longest finish life. That’s great, but who really wants to go to the trouble of sanding an entire new home?

One way to reduce the hassles of sanding new wood is to also pressure wash before painting. Gas-powered pressure washers typically deliver water at 1,500 to 3,500 psi — more than enough to eliminate mill glaze. Trouble is, this sort of hydro-pummelling also loosens surface fibers, especially with softwoods such as cedar and pine. And while fuzzy fibers are certainly thirsty enough to soak up paint, they also prematurely break off from underlying wood, letting the paint go along with it. This is where sanding comes in.

Let pressure-washed surfaces dry for two or three good days, then sand off the troublesome fuzz with a random orbit sander. It takes just a few quick passes over each board because a portion of the deglazing work was already done by water. For fastest results, use a 6-inch random orbit sander with an angle-grinder design. They’re more powerful than palm-style sanders, so you’ll cover ground faster.

Choosing and Applying Paint

Many still don’t think that today’s best exterior paints are latex, but it’s true. That’s because much more research and development has gone into advancing latex paints than oil-based formulations, especially for outdoor use. In fact, oil-based products are actually losing some of their former effectiveness as traditional formulas have been altered to boost safety and reduce environmental impact. The biggest difference has to do with adhesion and crack resistance.

In general, the best exterior latex is 100 percent acrylic. Not all latex formulations are, so read the fine print. Acrylic paint sticks better and retains the ability to expand and contract with changes in underlying wood — something oil-based paints have never been good at. Adhesion and flexibility translate into a more durable coating that looks better longer. The best source of current information on exterior latex paint performance comes from Consumer Reports. They publish annual results on comparative performance from brand to brand, and the differences are significant. The best exterior latex paints (made by California, Pratt & Lambert and Glidden) still rate excellent in appearance after nine years. The worst have deteriorated to just “good” after only three years.

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