Painting Shortcuts or Painting Over Moisture Lead to Paint Failure on Buildings InspectAPedia® -
Bad painting shortcuts or painting over moisture both lead to early paint failures on buildings.
What are the most common painting mistakes that we should avoid when painting a building?
How to diagnose the cause of failing paint on a building exterior or interior
Paint failure diagnosis checklists for the building exterior & interior
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Here we discuss two common causes of painting failure: taking shortcuts in the paint job and painting over moisture. This article series reviews common building exterior & interior painting
mistakes, describes how to diagnose paint failures on buildings, and outlines a procedure for diagnostic field inspection & lab testing of failed painted surfaces. We include photographs of paint failures on buildings and more photos of forensic paint laboratory examination of samples of failed
paint useful to assist in diagnosing the probable cause of each type of paint failure.
Our page top photo shows another painter's shortcut: skim-coating with crack filler was applied over the entire building as a substitute for removing old and loose paint. The new paint job cracked and failed in just a few months. Readers should also see Paint Failure Case Photographs-SITE and then Paint Failure Case Photographs-LAB, and see PAINT & STAIN GUIDE, EXTERIOR for a guide to the selection and proper application of paints and stains on exterior wood surfaces.
Failure to properly prepare the surface for painting is the most often cited cause of poor results or short life of the paint job. This includes failure to clean off loose dirt and debris, failure to remove loose or failing existing paint, and other similar mistakes detailed at PAINTING MISTAKE - BAD SURFACE PREP. Our page top photo shows a thick skim coat of crack filler that a painter used to try to smooth the to-be-painted surface as a shortcut instead of removing loose and alligatored paint. The result was a rapid failure of the paint job and an ugly lawsuit.
Spraying paint onto an existing painted surface without also brushing or rolling out the paint to work it into the surface. This often leaves paint on either side of but not inside of fine cracks and defects in the painted surface, resulting in a shorter life of the new coating.
Our photo (above-left ) shows a Poughkeepsie, NY house painted by the author and Art Cady ca 1986. The wood shingles presented a challenge both in surface preparation (uneven, soft surface) and in paint application. We found that working as a team, one man spraying and the second rolling and brushing out the paint allowed us to get the paint onto the surface quickly but still apply it securely to the building. Spraying alone is fast and can work on some new building surfaces (smooth one-coat stucco, for example) if the surface has been properly prepped.
Failing to mix the paint adequately. Poor mixing can result in an uneven distribution of paint vehicle and paint binder or uneven
color distribution in the paint. Inadequate binder in sections of paint lead to early paint adhesion failures.
Not putting paint on extra surfaces of wood to be painted on its exposed surface:
Omitting priming the back and ends and cut ends of clapboard siding
Omitting priming the back and ends of floor trim to be installed in a basement subject to moisture or damp floors
Skipping application of primer on new or incompatible surfaces
Over-thinning the paint to be applied (diluted binder)
Using a special purpose or shortcut super-fast drying primer or other primer not recommended by the manufacturer of the finish coating as the entire surface body primer
PAINT OVER MOISTURE - Painting Over Improper Surface Moisture or Painting Under Other Improper Weather Conditions
Painting over wet or damp surfaces such as from rain, morning dew, or interior leaks. When painting new stucco, sufficient time is necessary to allow moisture to evaporate from the surface. See PAINT on STUCCCO, FAILURES.
Painting with a water-based paint (acrylic paint or latex paint) or any water borne paint when rain is expected soon. Typically
the manufacturer requires at least four hours of drying time before expected rain. If rain arrives and wets the surface before the paint
has been sufficiently dried, the paint coating is likely to be damaged, resulting in a reduced life and possibly pigment loss or adhesion failures.
Inadequate checks for surface moisture: Painting all surfaces after measuring for "ok" moisture or temperature on one area of a building, while ignoring variations in temperature, moisture, or condition of other surfaces
Painting directly on un-primed weathered, raw wood
Painting over cold surfaces or in cold weather (under 50 degF)
Painting over hot surfaces or in hot weather (over 90degF for sure) - see PAINTING IN SUN and PAINTING IN WIND below.
Applying paint too thickly to the surface (runs, wrinkles). Most paint manufacturers specify the wet thickness with which paint should be applied. A wet paint thickness gauge can be used to double check the application during painting.
Painting on High pH Surfaces such as New Stucco
Painting too soon over new stucco exteriors or on a building where stucco was not properly mixed, applied, or cured can lead to early paint failure and efflorescence. See PAINT on STUCCCO, FAILURES for details.
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Paint and Surface Coatings, Theory and Practice [purchase at Amazon.com], R. Lambourne & T.A. Strivens, Ed., Woodhead Publishing Ltd., William Andrew Publishing, 1999 ISBN 1-85573-348 X & 1-884207-73-1 [This is perhaps the leading reference on modern paints and coatings, but is a difficult text to obtain, and is a bit short on field investigation methods - DF]
Analysis of Modern Paints, Thomas J.S. Learner, Research in Conservation, 2004 ISBN 0-89236-779-2 [Chemistry of modern paints, overview of analytical methods, pyrolysis-gas chromatography signatures of basic modern paints and their constituents, Fourier transform infrared spectroscopy for paint analysis, direct temperature-resolved mass spectrometry, and analysis in practice - technical reference useful for forensic paint science, focused on art works -DF]
Seeing Through Paintings, Physical Examination in Art Historical Studies, Andrea Kirsh, Rustin S. Levenson, Materials in Fine Arts, 2000 ISBN 99-051835 [ forensic science, technical reference, focused on art works - DF]
Paint Handbook: testing, selection, application, troubleshooting, surface preparation, etc., Guy E. Weismantel, Ed., McGraw Hill Book Company, 1981 [Excellent but a bit obsolete paint theory and practice, also a bit light on field investigation methods, out of print, available used-DF]
Understanding Ventilation, John Bower, The Healthy House Institute, ISBN 0-9637156-5-8, 1995 [General building science-DF - ** Particularly useful text. Mr. Bower has retired from the field but his book continues to be important]
"Moisture Control in Buildings: Putting Building Science in Green Building," Alex Wilson, Environmental Building News, Vol. 12. No. 5. [Good tutorial, "Moisture 101" outlining the physics of moisture movement in buildings and a good but incomplete list of general suggestions for moisture control - inadequate attention given to exterior conditions such as roof and surface drainage defects which are among the most-common sources of building moisture and water entry.--DJF]
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