Proper Prep: Sanding and masking outdoor wood

You can be a great contractor, but if your outdoor wood weathers badly, your reputation and bottom line will suffer. Long-lived outdoor wood finishing begins with proper prep, and proper prep always involves sanding in one form or another. It’s one of the most misunderstood parts of finishing decks, fences, gazebos, wood siding, soffit and fascia, but also the most important. Improper sanding (or no sanding at all) is the single biggest reason outdoor paints and stains fail before their time. Sand efficiently and your outdoor finishes will last about twice as long. Here’s how to make sanding practical in the real world of contracting.

Sanding Tactic#1: Convince clients to pay for it.

nice_paintSanding takes time, and clients don’t automatically see the value in making smooth outdoor wood smoother than when it came off the lumber truck. What clients almost never realize is that sanding before paint or stain isn’t about smoothness. It’s an investment that pays off in longer finish life. Sanding makes an even bigger difference on repainting jobs. If you can’t work compensation somewhere into your contracts for sanding before finishing outdoor wood, then don’t paint or stain. Better to leave the wood bare for someone else to finish and take the hit. Failed finishes always make you look bad, and will almost certainly be considered your problem.

Sanding Tactic#2: Use efficient equipment.

random_orbit_adjustmentSanding doesn’t have to be pain if you choose the right tools for outdoor work:

  1. A 6” angle-style random orbit sander is ideal for bulk surfaces.
  2. A 5” palm-style random orbit sander is made for light to medium-duty use in open spaces.
  3. A professional-grade detail sander is for intricate jobs that other sanders can’t reach.

6” random orbit sanders built around an angle grinder style motor are roughly 50% more productive than their smaller, 5” counterparts. The best include two random orbit pattern settings: one for coarse work and the other for finer results. I leave mine on “coarse” almost all the time since bulk removal is what I’m after with these machines. An 80-grit disk is all I ever use on 6” random orbits outdoors.

5” random orbits are lighter, more maneuverable and less tiring than 6” models. I keep a 120-grit disk on these machines, grabbing this tool when I want something finer than 80-grit.

For years after detail sanders became popular in the early 1990s, they were too small and weak to be useful for contractors. That’s changed to the point where power and design features now make these tools a must-have item for anyone in the renovation business.

Sanding Tactic#3: Choose the best abrasives.

sanding_disksIn a perfect world, the ideal sanding abrasive would perform just as well 20 minutes after beginning to use it as it did when new. The closer an abrasive comes to this ideal, the better it is.

So what makes a great sanding abrasive: long life, resistance to clogging and consistent grit performance. Cheap sandpapers do cost less at first, but they’ll end up costing you way more on labour. For every dollar you save buying bargain abrasives, you might lose five bucks in slower productivity and unnecessary time spent changing sand paper.

sanding_disk_80-gritSanded wood is thirsty wood, and thirsty wood hangs onto outdoor finishes longer. It’s as simple as that. New wood – especially new pressure-treated wood – is simply too smooth and too burnished to absorb paints and stains as it needs to. Poor absorption means poor adhesion and premature peeling. You look bad and your projects look bad. Field tests show that 60-grit abrasives create the best surface absorption, but it’s too rough for most clients. Wood sanded with 80-grit abrasives are smoother and almost as absorbent. Don’t sand smoother than this while prepping outdoor surfaces for stains. 120-grit is the upper limit for painted surfaces.

You could be the best builder on the planet, but if the visible outdoor wood on your projects looks bad a few years after you’re done, your reputation will go the same way. Get good at sanding outdoor wood and you’ll be way ahead.

Testing Pro Grade Abrasives

flex_back_sandpaperThe most recent entry in the high-end abrasive category comes from 3M. I’ve been testing two items from their Pro Grade line: round sanding discs for random orbit sanders, and a unique, flexible-backed line of hand-held sandpapers. Both are better than the best abrasives I’ve used so far. The Pro Grade Precision Ultra Flexible Sanding Roll has abrasive particles applied to a rubberized, non-paper backing. The high friction surface of this backing makes it easier to grip while hand sanding, and the flexibility lets the abrasive conform to molding and trim. The Pro Grade round hook-and-loop discs are noticeably thicker than usual, they last long and resist clogging and have better life than any other disks I’ve used.

Sidebar: Masking Outdoor Surfaces

scotch_blue_closeOutdoor finishing is about a whole lot more than just throwing a coat of paint on something and calling it a day. Artistry sometimes comes into play and this can involve masking. And one of the latest innovations in the fast-improving realm of masking products is exterior masking tape. Why bother with something different?

In my tests exterior masking tapes are better outdoors in three ways. They’re able to conform to uneven surfaces and seal out paint better than interior tape; outdoor tapes resist UV rays and water better than indoor versions because they’re made of plastic not paper; and the adhesives resist over-sticking and breaking apart caused by heat, sunlight and high moisture.

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Posted on September 2nd, 2015

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