15 Tips for Tough Exterior Surfaces
Every paint job has its challenges—but due to the surfaces or the setting, some are more challenging than others. We asked some seasoned pros to share their prep and painting strategies for a variety of surface situations.
PRO TIPSTER: Bob Cusumano, president of Coatings Consultants, Palm Beach Gardens, FL
Cusumano analyzes paint failures, writes coating project specifications, and provides expert witness testimony.
TIP #1 Testing, Testing
The challenges with tilt-up concrete structures start with the fact the horizontal forms use a curing or bond-breaking oil to keep the concrete from sticking. “Most of the oil will dissipate from exposure, but if it’s put on too heavy, it will interfere with paint adhesion,” Cusumano says. “I have seen entire tilt-up warehouses have to be stripped because the paint was peeling everywhere.” His advice: do a sample, let the paint cure, and then do an adhesion test.
TIP #2 Rough Things Up
On some jobs, the panels are so hard and smooth that it hinders mechanical adhesion. Cusumano advises you roughen smooth surfaces through sweep abrasive blasting or acid-etching before applying a coating.
TIP # 3 Know What You’re Working With
One of the newer issues is the use of more fly ash and less Portland cement in concrete as a ‘green’ solution. Because fly ash is a by-product of burning coal, it tends to be oily, which makes it difficult for some acrylic and latex paints to adhere to.
Cusumano advises, “Ask the contractor what the mix is. This is a relatively new issue and there hasn’t been much testing yet, so no one’s sure what the percent is that’s OK.”
TIP #4 Pay Attention to Permeability
The rule of thumb is that you should wait 30 days before painting concrete. “But there’s nothing magic about that number,” Cusumano says. “If the paint system has a low permeability, it could cause the paint to blister when the moisture tries to escape.” Use primers and coatings with a high permeability—particularly if time doesn’t allow for a full cure.
TIP #5 Use Hot-Stucco or Hot-Concrete Primers
Concrete has a high pH when it’s poured, meaning that it’s very alkaline. Even with the correct primer, be aware that you need to have a highly permeable topcoat to allow moisture to escape.
However, with new construction, you may have to paint before it drops to an ideal pH. “If you’re using white paint, you don’t worry about alkali burn,” says Cusumano. “But if you’re using tinted paints, the reaction can cause it to bleach out and you get a blotted appearance.”
TIP #6 Exclude Bugholes from Your Scope of Work
Small holes in the concrete, called honeycomb or bugholes, need to be filled—and you won’t know how good or bad the pour is when you submit your bid.
“The question is, ‘whose job is it to fill all the bugholes?’ Cusumano says. “If you don’t exclude bugholes from your scope of work, you could be left with significant patching.”
TIP #7 Avoid Caulking Conflicts
To complicate matters, the caulking contractor is going to want to caulk sealing joints before the paint job because some caulk manufacturers won’t warranty it otherwise. Meanwhile, painters prefer to caulk after the primer and paint are applied for the best adhesion. “It can get the caulking and painting contractors into finger-pointing mode,” says Cusumano.
He advises you never guarantee paint that has to be applied over sealant; you can often solve the problem by using a tinted sealant that doesn’t need to be painted.
PRO TIPSTER: Dave Wenners and Carly Baker, co-owners of C & D Painting, Newburyport, MA
Situated on the eastern seaboard of Massachusetts, Wenners and Baker deal with the elements year-round. Wenners says, “The key is knowing which product is appropriate for which seasons and conditions.”
TIP #8 Let it Breathe
One of the big problems Wenners sees is that clients think their house should be watertight, so they caulk everywhere—even at the bottom of clapboards, where it is designed to breathe. Exacerbating the problem, about five years ago, Massachusetts offered caulking incentives for homeowners to caulk every square inch of their houses. “Now they’re finding that it actually did more damage than good,” Wenners says.
He advises you never seal up a house too tight. Make sure it’s caulked only where it needs to be, and breathes where it should.
TIP #9 Be Sand Smart
New England is famous for its brutal winters, but this year was worse than most. Wenners cites a client whose beach house had been stained last summer, but looked like it had been sandblasted after the high winds in winter: Little areas had started out as a pinhole, and grew to be seriously damaged.
When blowing sand is an issue, an oil-based product or epoxy may hold up better. And always avoid painting on days when sand can get blown into freshly sprayed paint.
TIP #10 When Needed, Turn to the Experts
In addition to water and blowing sand, old coastal houses often still have lead paint, which means dealing with constantly changing rules and regulations on lead-paint mitigation.
Wenners suggests you keep your local lead inspector’s number on speed dial. He’ll know the best current collection and containment solutions, and he can also help you educate the homeowner.
TIP #11 Keep Ahead of Coastal Salts
Salt, mold and mildew are ever-present issues on the coast—and all of them cause bonding problems. Sometimes a light power wash will do the trick; in other cases, scrubbing and agitating with a scrub brush and chemical solutions is required.
Wenners advises once you’ve power washed, get a primer on right away before new salt deposits hit the house.
PRO TIPSTER: Mark Miller, president of Performance Industrial, South Glens Falls, NY
According to Miller, the ideal preparation for steel is to sandblast all the way down to bare metal. “It removes all the paint, surface latents, rust, and inferior material that might be on there,” he says. “It’s the only way you can guarantee a sound, solid substrate that you can anchor the coating to.”
TIP #12 Good Prep Leads to Good Results
Pressure wash all surfaces first to remove contaminants such as oil, pitch, pollen or chemicals. After you’ve sandblasted down to bare metal, a three-part coating of epoxy primer, epoxy mid-coat, and a urethane topcoat is the ideal. Make sure to get the primer on immediately, because you can have overnight flash-rusting in all but the driest climates.
TIP #13 Make Plan B as Good as Plan A
If sandblasting isn’t an option, either because of budget or other factors, Miller says the next best solution is a very aggressive pressure wash: 4000 psi with an aggressive spinner tip to get as much loose and flaking paint off as possible. Hand tools—whether angle grinders, chippers, or pneumatic hammers—can then be used to remove as much of the remaining rust and coating as possible.
After pressure washing, use a rust-inhibiting pre-prime, which goes on clear over any tightly adhered rust, sealing it and preventing oxygen from getting in. Then, topcoat with the three other coating layers.
TIP #14 Be Thorough
When spraying or rolling, if you’re not thorough, there may be little spots you miss—known as holidays or pinholes—that allow water and oxygen to get in. Once they’re through the primer or topcoat, they’ll start attacking the metal again.
In addition to ensuring 100% coverage on primary surfaces, always do a stripe coat, hand-brushing all the nuts, bolts, seams, and right angles.
TIP #15 Know When to Walk Away
If a customer wants you to paint steel that’s rusted and has flaking paint, but they don’t want you to pressure wash or do an epoxy pre-prime, it’s going to fail.
“Walk away,” Miller says. “Go do a job where you’re appreciated and let someone else deal with the problems.”
It’s a good idea to incorporate the PDCA’s industry standard P17 about tilt-up concrete into your proposals: PDCA.org