A primer on exterior paint prep

Sanding, safety, application tips

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Add Comment Add Comment | Comments: 0 | Posted Oct. 29, 2010

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Sanding, safety, application tips

Paul Bianchina
Inman News

If you've let those exterior painting chores go all summer, now's the time to get to them. You don't want to leave any bare wood showing through fall and winter, where harsh weather can take their toll on siding and trim. Luckily this isn't too tough of a project, and if you get after it on Saturday morning, you'll be all wrapped up before the games start on Sunday.

Prep work is key

The real key to getting that paint to blend in and stick is to prepare the surfaces correctly. That's going to take a little elbow grease and the right materials. But it'll keep you from having to do it again for several years.

First of all, you need to be sure that you've removed all of the old, peeling paint. It's obvious that since that layer of paint isn't stuck to the siding now, anything you put over it won't be stuck to the siding either.

You've got a couple of different options for removing the old paint. And quite honestly, none of them are particularly fun and exciting, but they have to be done. Try a few different methods, and see which one works best; you'll probably find that a combination of things is what does the trick:

  • Hand scraping: This can be done with a putty knife for very small areas, or with a paint scraper, of which there are several types available. Look for one that's comfortable in your hand, and that has reversible blades for more blade life. The ends of the blades should be rounded so they don't dig into the siding and gouge it.
  • Sanding: This can be done with a hand sanding block, or with an electric sander. Use an open-coat sandpaper, which won't clog up as quickly with paint particles. As you sand off the loose paint and get back into solid material, be sure to feather the edges of the solid paint so that your patched areas won't be as visible. There's also a tool made by Wager specifically for removing paint, called the Paint Eater, which uses a special 3M disk. It's more aggressive than sanding alone, and works well in combination with conventional sanding methods if you have a lot of paint to remove.
  • Pressure washers: Using a pressure washer to remove paint was popular for awhile, but to some degree has fallen out of favor. The amount of pressure needed to strip paint can damage wood siding, and can also force moisture into areas where you don't want it.
  • Chemical strippers and heat guns: There are a number of chemical strippers available that are painted onto the surface, allowed to sit, then hosed off or stripped off with a putty knife, taking the old paint with them. They can be useful in some smaller situations, but are also messy and expensive for larger jobs. Heat guns can be used to strip paint, but I strongly recommend against them for safety reasons.

Clean and prime

When you've removed the old paint from the areas where you need to work, you'll be down to bare wood. Next, you want to clean the areas so no dust remains. Again, you want to give the paint a solid surface to adhere to, and dust isn't that surface.

You can use a dusting brush, an old paint brush, a soft broom, or other tools to wipe down the areas and get the dust off. If you have a compressor, you can blow the dust off with air. You can also vacuum it off with a shop vacuum. The main thing is to get it clean and dust free. Check the area again and make sure all the remaining paint is solid, and the edges are feathered back.

All bare wood needs to be primed, which will do several very good things. The primer will seal the wood to prevent moisture from getting in, and it will seal things like knots and nail heads so they don't bleed through your finished paint. Primers also create an intermediate bond between the wood and the finished paint, which helps the two adhere to one another. That means that the finished paint will stick better and last longer over a prime coat than it will over bare wood alone.

Look for a primer that's compatible with the surface you're priming, such as wood, metal, etc., and with the type of finish paint you're using, such as latex. It also obviously has to be rated for exterior use. If you want to get things done quickly, look for a fast-drying primer, but you still need to be sure that it's completely dry before applying your top coat.

For the top coat, consider having a gallon of paint custom-matched to your existing siding, rather than rely on that old can of paint that's been sitting in the garage for 10 years. A fresh can of paint that's an exact match to what's on the house -- which is probably faded compared to what's in that old can -- will not only match better, it's going to last longer than the material in the old can that's lost a lot of it's usefulness.

Safety first

If your house was built prior to 1978, there's a good chance that you may also have some lead paint issues to deal with. Before doing any scraping or sanding of any old paint, check out the EPA's lead paint guidelines by visiting their website at www.epa.gov/lead, or contact the National Lead Information Center (NLIC) at 1-800-424-LEAD (5323).

Lead paint or not, when doing any sanding, grinding, scraping or other work, be sure you're wearing a dust mask or respirator, as well as some type of proper eye protection. When using chemical strippers, follow all of the manufacturer's specific safety instructions.

Remodeling and repair questions? E-mail Paul at paulbianchina@inman.com. All product reviews are based on the author's actual testing of free review samples provided by the manufacturers.

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