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Tuesday, April 05, 2011


Advice from the Pros:

Spring Repairs & Touch-ups

In our last post, we talked about what causes blisters, peeling, and other common paint problems; in this post, we'll tell you how to repair them and, as important, avoid these problems in the future. Proper preparation is the key, whether you're fixing a few blisters or repainting an entire house. Cleaning, sanding, and scraping aren't much fun, but think of it this way: the more time and attention you give to preparing the substrate, the longer the coating will last. In the end, you'll actually spend less time on a ladder, because your paint job will last much longer.

Cleaning
Over time, exterior paint will begin to oxidize from the sun's UV rays and will attract contaminants that interfere with the ability of new paint to adhere to the surface. That's why a thorough cleaning prior to any painting is so important, regardless of the size of the job.

Power_washing

For cleaning large areas, power washers are a popular cleaning option, but they aren't absolutely necessary for smaller repairs. To be effective, the power washer should operate at 2,500 PSI or more, but try to aim the spray wand so that it's angled down so you don't drive water up underneath the siding and into your walls. If held too close to some types of siding, like cedar shingles and clapboards, power washers can also damage wood fibers. But if used properly, power washers can help remove loose paint or stain as well as dirt as well as save you time and elbow grease. 

Don't just depend on the force of the water, though. With or without a power washer, use a detergent such as Benjamin Moore's "Clean" 318. This is a pre-mixed multi-purpose cleaner that can be used on wood, vinyl, cement, and stucco to remove dirt, and chalk. Use a bristle brush to scrub the surface clean, and then rinse with clear water. Mildew is a common problem on the exteriors and most common on the north side of the home or in areas that get little to no sun light. Mildew should be removed using a commercial mildew remover like 318 Clean or a solution of 1 part Bleach and 3 parts water. Using a garden pump spray, spray the contaminated area and allow to sit for a few minutes then power wash or rinse thoroughly.

Scraping & Sanding
Once the substrate is clean, look closely for remaining blisters and for loose or peeling paint that scrubbing or power washing hasn't removed and use a paint scraper so that only sound paint remains, followed up with sanding with 120-grit paper to feather the edges smooth. Smaller areas of flaking paint can often just be wire-brushed and then sanded smooth, again with a 120 grit paper. When you're done, be sure to rinse thoroughly again to remove debris left behind. If you discover any rot, repair or replace the affected area.

Keep in mind that if you're working on a home built prior to 1978, there's a chance that the old paint may contain lead, which presents a number of health hazards to both children and adults. Cleaning isn't a problem, but sanding or scraping lead-based paint without wearing a NIOSH-approved respirator and careful containment and clean-up of debris can lead to exposure to lead dust. Before you start, find out how to protect yourself and your family by contacting the National Lead Information Hotline at 1-800-424-LEAD or log on to www.epa.gov/lead.

Drying
Whenever you add moisture to a porous substrate like wood or concrete, you have to give it plenty of time to dry out before you paint or prime it. If you've used a power washer, it might take as long as 2 or 3 days even in ideal drying conditions--warm temperatures and low humidity--before the surface is ready for a finish. Some paint stores have moisture meters available for rent that will allow you to check the substrate's moisture content, which should be between 12% and 15%.

Priming
Priming isn't always required, but even self-priming paints like Aura Exterior may benefit from a primer when used over some surfaces. For example, bleeding woods such as cedar or redwood should first be primed with an alkyd-based primer to ensure the tannins in the wood don't leach through your finish coat. Bare ferrous metal surfaces also need to be primed to prevent the surface from rusting. For the best advice about whether or not you need to prime, check with the manufacturer or the instructions posted on the label on the can.

If you plan to paint, watch the temperatures this time of year. Temperatures should be above 40 degrees (50 degrees for primers) when the paint is applied and stay that way for at least 2-3 hours. See our post on cool weather painting for more details.

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Comments

George - can you let us know which Benjamin Moore product you applied to the ceiling? Also, did it peel back down to the bare plaster?

I have a problem with peeling on a ceiling in a very old house with plaster ceilings. The problem is peeling. I have scraped away the peeling, sanding and spackling the bad spots. Then I repainted using your combined primer and ceiling paint. Within a few days it peeled again. Help please!

I think the cleaning part is the most crucial here. Some people miss the spots and corners that are hard to clean, so paint usually doesn't stick well to the surface. But thanks for pointing out that rigorous cleaning can also create some damage.

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