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Exterior Painting Prep Tips

Exterior Scraping, Cleaning & Caulking Tips

The majority of homeowners and workers seem to desire instant gratification. The condition is growing worse each year. A homeowner decides to paint something in a weekend or just one day. They jump right in and paint. This is a big mistake. You must restrain yourself or your mate and have them perform the necessary surface preparation.

Remember, paint is nothing more than colored glue. When was the last time you saw glue that will stick well to a dirty, dusty surface?


This is fairly straightforward. Loose paint must be removed. You can do it in any number of ways. Flat putty knives, or "pull" scrapers work very well. You may wish to use both tools. Pull scrapers are those that have shallow U shaped cutting blades. They really cut through old oil paints.

I urge you to wear goggles when scraping overhead. I have scratched my eyeball cornea on two occasions from paint scrapings. It is very painful and costs lots of money for medical care! Wear goggles!

Scraping is the first operation in surface preparation. Remove as much loose paint as possible. You then wash and rinse. I guarantee you that you will have to scrape certain areas again. Look closely at locations where bare wood is exposed. Where paint begins, the film may have lifted ever so slightly. Scrape these spots again. Resist the temptation to sand the edges of the paint smooth. Why? Because if the paint is old - say before 1978 - there is a great chance it contains lead. All you will be doing is generating toxic lead dust!

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This is by far the most important aspect of surface preparation. I don't care how wet you get, you must hand wash your house. Use a large grout sponge and copious amounts of soapy water. Regular liquid dish soap will do just fine. It produces lots of suds. Experiment with soft brushes or whatever to make the job easier. Rinse the washed areas quickly so the dirty water doesn't dry!

Avoid pressure washing. Why? For one, it doesn't remove all of the dirt! It can also drive water deep into or behind wood siding or trim. I have seen people spray upwards on a soffit. They flood the soffit, the wood swells and 2 months later the new paint peels off! Pressure washers are instant gratification tools!


Water that enters the end grain of siding or trim boards causes paint failure. You must do what you can to minimize and/or eliminate this kind of intrusion. I prefer the standard acrylic latex caulks for this purpose. Do NOT caulk the bottom edge of clapboard siding! These boards must be allowed to move and breathe. That small crack allows the siding to move. It can also allows water vapor to escape.

Always wipe caulking with a moist sponge as soon as it is applied. This will produce a clean, crisp joint instead of a finger smeared mess.

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2 Responses to Exterior Painting Prep Tips

  1. You mention scrape and then wash. Makes sense to me but I have seen painters do the reverse. You mention soap. No bleach to deal with mildew?

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