Removing Exterior Paint Safely

Summary of Expert Advice from Preservation Brief 10

Chipped, cracked, and peeling paint on a red door
Tim Graham/Getty Images (cropped)

What are the safest ways to remove paint? Does exterior paint need to be taken off down to the bare wood? Do heat guns really work? These are questions homeowners around the world face. You are not alone. Fortunately, the paint problems of one person's home are the same faced by other homeowners. Believe it or not, the U.S. Department of the Interior has come to the rescue.

It wasn't until 1966 that the U.S. became serious about preserving its "historic heritage." Congress passed the National Historic Preservation Act and charged the National Park Service (NPS) with supporting historic preservation programs and activities.

Their handy series of preservation briefs are geared toward historic buildings, but the information is great professional advice that anyone can use.

Exterior Paint Problems on Historic WoodworkPreservation Brief 10, was written by Kay D. Weeks and David W. Look, AIA for the Technical Preservation Services. Although written back in 1982 for historic preservationists, these recommendations are good starting points for homeowners to come to terms with what needs to be done. Here is a summary of the historic preservation guidance and expertise for painting exterior wood siding — with links to more information from the original brief.

Selecting the Safest Method to Remove Paint

Removing paint involves work — that is, the manual labor of abrasion. How much time and effort are put into paint removal (or paint preparation) is a judgment call and may be the most difficult decision you make. Basically, you can remove paint from your home's exterior siding by three methods:

1. Abrasive: rubbing, scraping, sanding, and generally using friction. Use a putty knife and/or a paint scraper to dislodge anything loose. Then use sandpaper (orbital or belt sanders are okay) to smooth each area. Do not use rotary drill attachments (rotary sanders and rotary wire strippers), do not waterblast or pressure wash, and do not sandblast. These abrasive methods may be too harsh to the siding itself.

Pressure washing above 600 psi may force moisture into places where it should not go. A gentle garden hose for cleaning up is okay.

2. Thermal and Abrasive: heating paint to a melting point and then scraping it from the surface. For thick layers of built-up paint, use an electric heat plate, an electric heat gun, or a hot air gun that heats from 500°F to 800°F. The blow torch is not recommended.

3. Chemical and Abrasive: using a chemical reaction to soften the paint to make it easier to scrape away. For many reasons, use chemicals only as a supplement to other methods of paint removal. They are too dangerous for you and the environment. Two classes of chemicals are solvent-based strippers and caustic strippers. A third category is "biochemical," which may be marketed as "bio-" or "eco-" but it's the "chemical" part that makes it work.

Paint Removal Precautions

Any house built before 1978 may have lead-based paint. Do you really want to remove it? Also, don't substitute speed for safety. Only use the recommended methods listed above. Keep yourself safe and your house in one piece.

Paint Surface Conditions and Recommended Treatments

Ask yourself why you want to paint your house. If there is no paint failure, adding another layer of paint may actually be harmful.

"When paint builds up to a thickness of approximately 1/16" (approximately 16 to 30 layers)," say the authors of Preservation Brief 10, "one or more extra coats of paint may be enough to trigger cracking and peeling in limited or even widespread areas of the building's surface." Repainting buildings for cosmetic reasons is not always good reasoning.

Sometimes you don't need to remove old paint at all, especially for these conditions:

  • Dirt and Grime: Sometimes road dirt and salt can make siding look worse than it is. Clean it with "l/2 cup of household detergent in a gallon of water with a medium soft bristle brush" and then a gentle hosing.
  • Mildew: Clean with a medium soft brush using "one cup non-ammoniated detergent, one quart household bleach, and one gallon water." Try to open the area to the sun to avoid further mildew.
  • Paint chalking is that white film on the surface of old paint that is breaking down. Clean the area with a medium soft brush using "l/2 cup household detergent to one gallon water."
  • Stained paint occurs most often from metal or wood becoming moist and coloring the painted surface. Determine the cause of the stain, but it's usually unnecessary to remove the paint.

Limited paint removal can be considered for these conditions:

  • Paint Crazing: Crazing is "fine, jagged interconnected breaks in the top layer of paint." It happens when a house has many layers of paint that become hard and brittle, not allowing expansion and contraction with the wood. Sand off a layer and repaint.
  • Paint Blistering: "To distinguish between solvent blistering and blistering caused by moisture, a blister should be cut open."
  • Wrinkled Paint: This happens when the paint has been put on incorrectly. The authors call this an "error in application."

In a historic building, leave a small out-of-the-way patch untouched for archival purposes. A record of all of the paint layers through the history of the house is useful for future historians. Unfortunately, some conditions require complete removal of exterior paint:

  • Paint Peeling: Before painting, remove sources of moisture inside and outside, as described by the authors: "Excess interior moisture should be removed from the building through installation of exhaust fans and vents. Exterior moisture should be eliminated by correcting the following conditions prior to repainting: faulty flashing; leaking gutters; defective roof shingles; cracks and holes in siding and trim; deteriorated caulking in joints and seams; and shrubbery growing too close to painted wood."
  • Cracking and Alligatoring: These symptoms are "advanced stages of crazing."

General Paint Type Recommendations

Paint type is not the same as paint color. The type of paint to choose depends on the conditions, and most old (historic) homes will have oil-based paint somewhere in the mix. Remembering that this article was written in 1982, these authors seem to like oil-based paints. They say, "The reason for recommending oil rather than latex paints is that a coat of latex paint applied directly over old oil paint is more apt to fail."

Justification for Paint Removal

A major purpose for exterior paint is to keep the moisture out of your home. Often you don't need to remove paint down to the bare wood. To do so usually requires harsh methods that may damage the wood. Also, the layers of paint on a house are like the rings of a tree trunk — they provide a history that future owners may want to analyze in a laboratory during an architectural investigation.

Painting a house every 5 to 8 years protects exterior wood siding from moisture penetration — and can add some zing to your home's curb appeal.

Regular maintenance of a house will include "mere cleaning, scraping, and hand sanding." Where there is a "paint failure," determine and fix the cause before you even begin a painting project. Treating paint problems often means a total painting of the structure may be unnecessary.

However, if you determine that you need to paint your house, keep two things in mind before you repaint: (1) only remove the top layer of paint down to the next sound layer; and (2) use the gentlest means possible.

The authors summarize their findings by repeating their cautious approach to painting and paint removal. The bottom line is this: "There is no completely safe and effective method of removing old paint from exterior woodwork."

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Craven, Jackie. "Removing Exterior Paint Safely." ThoughtCo, Oct. 24, 2017, thoughtco.com/how-to-remove-exterior-paint-safely-3884401. Craven, Jackie. (2017, October 24). Removing Exterior Paint Safely. Retrieved from https://www.thoughtco.com/how-to-remove-exterior-paint-safely-3884401 Craven, Jackie. "Removing Exterior Paint Safely." ThoughtCo. https://www.thoughtco.com/how-to-remove-exterior-paint-safely-3884401 (accessed November 23, 2017).