Alligatored paint (C) Daniel Friedman Common Building Painting Mistakes to Avoid
26 ways to get a bad paint-job on a building

  • PAINTING MISTAKES - CONTENTS: 26 examples of inadequate surface preparation that lead to building paint failures. What are the most common painting mistakes that we should avoid when painting a building?
    • POST a QUESTION or READ FAQs about building exterior or interior paint job mistakes and paint failiures - how to avoid paint problems on buildings

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This article desribes and illustrates 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 a horrible paint job on a building exterior: the painter simply painted over loose, alligatored paint.

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Common Building Painting Mistakes to Avoid

Photograph of  peeling paint on a building exterior - can you diagnose this failure by eye?Experts representing paint manufacturers see many field failures of painted surfaces, often arising from a common cause.

[Click to enlarge any image]

But getting a clear answer from these professionals can be tricky: the painting contractor is their customer, not the building owner.

Therefore, while most paint failures are due to poor surface preparation or painting in improper conditions of temperature or moisture, the "expert" may be reluctant to say so.

Importantly, other paint failures are due to construction errors, building ventilation or vapor barrier errors, building leaks, or improper maintenance. It is important to understand why a paint failure occurred before re-painting a building.

Otherwise the expense of a new paint job may be wasted.

"Improper or inadequate surface preparation is by far the most common cause of house paint failures such as blistering, peeling and staining. If the new paint is separating from the old coat of paint, it is most likely due to chalking or some contaminant on the old paint that prevents the new paint from penetrating and binding to the old painted surface.

If the peeling failure is down to the bare wood, it is most likely that the problem is a result of too much moisture within the wall, forcing itself out, taking the entire paint film with it."

"Over 65% of all paint failures can be attributed to poor or improper surface preparation. Two of the major causes of paint failure on exterior wood surfaces are either moisture passing through the substrate from the interior, or exterior sources of moisture getting behind the paint film. Temperature and humidity have major effects upon drying and ultimately upon the characteristics of the paint film. These effects will always determine the actual appearance and performance of the paint itself.

Photograph of  peeling paint on a building exterior - can you diagnose this failure by eye?Paint should be applied at temperatures of 70o F, (21o C), ideally, plus or minus 20o F (12o C) - unless product specifications state otherwise. A surface should not be painted if its temperature is within 5o F of the dew point or the relative humidity is above 85%." -- PPG Exterior Failures.

The follow sections of this document form a checklist of building and site conditions leading to paint failures (such as peeling paint, blistering paint, chalking paint, cracking or alligatoring paint, or bleeding and stains through paint--terms defined below).

The focus is on failures of painted wood surfaces on building exteriors but the paint failure diagnostic procedure can be generalized to other surfaces inside and out.

The three key steps to successful painting are

1. Prepare the surface,

2. Prepare the surface,

3. Prepare the surface.

- DF (moderator) and a panel of experienced house painters at ASHI ca1988 Paint Failures Seminar. Also see PAINT SURFACE PREPARATION.

But other than inadequate surface preparation, here are some other very common house painting mistakes:

BAD PAINTING SURFACE PREPARATION - 26 Painting Mistakes That Mean a Bad Paint Job with a Short Life - causes of early paint job failure

  1. Removing only the obviously-loose paint, leaving poorly-secured paint, leaving thick edges of old paint where blisters or old peeled paint were inadequately removed.
  2. Using paint to try to fill gaps where caulk should have been applied.
  3. Using a spackling compound or filler intended for holes or cracks to "smooth" large building surface areas (skim coating) such as skim coating in order to apply paint over alligatored or poorly-adhered old paint. More thickness of fillers, paints, primers,or magic gluey coatings on the surface of un-sound paint are unlikely to work. A case study of this foul-up is at PAINT FAILURE CASE PHOTOS, SITE.
  4. Painting over thinly-cracked, or peeling painted surfaces
  5. Painting over old, existing thick, alligatored paint
  6. Painting over dusty or dirty surfaces. See PAINT SURFACE PREPARATION
  7. Painting over mold (which many sources incorrectly call "mildew"). Painting over moldy surfaces without adequate cleaning and surface preparation such as power washing, disinfection, and light sanding, likely to lead to rapid mold re-growth in the paint and possibly to a paint adhesion failure, even if a paint "mildewcide" or fungicidal additive was used.

    Also see Mildewed Exteriors?.

    Parmetol, a wood preservativerecommended by the manufacturer was used as a fungicidal additive to paint on the Blue Poplar wood sculpture in Amsterdam, by sculptor artist Mari Shields whose huge wood tree sculptures and stunning works can be found at a number of locations listed at her website:[ - art conservation consult DF-artist MS 2010]
  8. Poor paint job (C) Daniel Friedman

    As we discuss at PAINT FALURE, DIAGNOSIS, CURE, PREVENTION, our photo (left) shows a new paint job that failed before the job was even finished, on a historic property: the Justin Smith Morrill Homestead in Vermont.

    While most of the paint failures on this building were due to use of improper paint or defective product, here we saw peeling and loss of adhesion over moldy wood.

    A combination of failure to properly clean the wood surface before painting, painting under too hot or too wet conditions, and failure to use an effective primer and properly formulated top coat can conspire together to give a messy paint job failure on some projects.

  9. Painting over oily or other-contaminated surfaces
  10. Painting over high pH surfaces on stucco, such as new stucco that has not adequately cured or stucco that needed additional wash and surface neutralization can cause white blooms of efflorescence and early paint failures; see PAINT on STUCCO, FAILURES for details.
  11. Painting over glossy hard paint surfaces without adequate preparation such as light sanding or use of a chemical de-glosser, likely to lead to an adhesion failure.
  12. Painting over mill-glazed surfaces such as trim or cedar or pine clapboards. See PAINT SURFACE PREPARATION Also see Unfinished Siding & Trim.
  13. Painting over new masonry or new stucco that has not adequately cured.
  14. Painting over old oxidized chalky paint or stain
  15. Painting over rot or insect-damaged wood
  16. Poor prep trim paint job (C) Daniel Friedman

    As we discuss at PAINT FALURE, DIAGNOSIS, CURE, PREVENTION, our photo (left) shows a new paint job over old rot.

    It looks as if the painter used a rather soft wood filler to try to repair the rotted window sill, and if you look closely (click the image to enlarge it) you'll see that the paint is already coming off - months after this costly renovation.

    Where sill rot is limited, rather than replacing the entire sill or frame, we find it easier to cut out and replace a rotted window sill by piecing in a custom-cut repair segment, perhaps using treated wood (let it dry before painting) glued in place.

    We have also made occasional use of wood restoration epoxy products such as those made by Abatron, Inc. to restore and save valuable trim that would be costly to replace. But slopping on some putty and paint, as was done here is not a durable job.

  17. Painting over silicone caulk (which in many cases is not paintable)
  18. Painting in hot sun or dry wind: painting in sun or wind can be a particular problem when painting new stucco surfaces. See PAINTING in SUN or WIND and see PAINT on STUCCO, FAILURES for details of the problems this causes on stucco.
  19. Painting the second coat before the first paint coating has adequately dried
  20. Painting without reading the manufacturer's instructions for mixing, thinning, surface prep, temperature conditions, etc.
  21. Soaking building cavities: surface preparation for painting by improper use of a power washer: spraying "up" on a clapboard building forcing water into the building wall cavities, (risking hidden mold contamination or a moisture problem leading to paint failure), or spraying too-close to the building surface, causing gouging and undesirable loss of surface material
  22. Surface washing using chemicals or bleach without adequate wash-off of the chemical or cleaner itself
  23. Painting on wet surfaces - failure to measure moisture levels or measuring only the "dry" areas but painting over other wet areas of a building. Also see Moisture Impact on Paint.
  24. Painting over incompatible old paint - leading to poor adhesion, wrinkling, cracking, paint fall-off. See INCOMPATIBLE PAINTS.
  25. Painting with the wrong type of paint for the surface or environment, such as using an interior paint outside. See INCOMPATIBLE PAINTS.
  26. Sanding with a grinder carelessly, leaving sanding marks and gouges that ruin the surface and telegraph through the new paint job - may not reduce paint adhesion but may result in a cosmetic issue with the work.
  27. Poor prep trim paint job (C) Daniel Friedman

    As we discuss at PAINT FALURE, DIAGNOSIS, CURE, PREVENTION, our photo (left) shows the condition of a nearly brand-new paint job on an older home in Poughkeepsie, NY.

    We noticed that old paint was left on the surface with no feathering of the edges of the few spots where paint had been removed or had fallen off before the paint job.

    We noticed also that the painter tried to "seal" the loose paint by globbing on plenty of new paint - see that drip running down the trim board?

    Finally, we noticed that this new paint job was already failing - the split in the paint visible in the lower portion of the photograph.

    This paint job will have a shorter life than if the surface had been stripped, but then the painter (and owner who was selling his home) avoided a much higher cost of stripping lead-containing paint from an older building.

  28. Painting too thick: slopping on paint that runs down walls (see above and below)
  29. Poor prep trim paint job (C) Daniel Friedman

    As we discuss at PAINT FALURE, DIAGNOSIS, CURE, PREVENTION, our photo (left) shows the result of many coats of paint on a home built in Dutchess County NY in the 1700's. This was some of the thickest paint we have found on a building exterior.

    No tests for the presence of lead paint are necessary in a case like this - you know that lead paint is present. Y

    ou also can see that this paint job is cracking and that paint has been falling off of the building between paint jobs that involved little or no surface preparation.

  30. Painting too thin: over-thinning paint to extend its coverage dilutes the binders so that even if the new paint job looks great it may wear or fail prematurely

For a description of proper painting procedures see PAINT SURFACE PREPARATION. For a detailed guide to selecting and using exterior paints and stains, readers should also see PAINT & STAIN GUIDE, EXTERIOR.

Also see PAINT FALURE, DIAGNOSIS, CURE, PREVENTION and PAINTING MISTAKES for details of paint failure cause, diagnosis, cure and prevention.

Odors from paints and low-VOC or zero-VOC paints are also discussed at ODOR DIAGNOSIS CHECKLIST, PROCEDURE.

Continue reading at BAD SURFACE PREP


Suggested citation for this web page

PAINTING MISTAKES at - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.

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Frequently Asked Questions (FAQs)

Question: how to remove mold from a wood tree sculpture & prevent mold re-growth?

This may be unusual, but I'm a sculptor. Part of my output is expressed using lime wood branches, clippings. I've noticed that mold has appreared from the cut ends of these branches and cuttings. Can I retard this or reradicate it using a spray/chemical? I'd appreciate any advice or someone to whom reference can be made. Yours sincerely, I.C. 6/8/2013


Thank you for the interesting question about mold growth on wood branches used in a sculpture - it helps us realize where we need to work on making our text more clear or more complete. A competent onsite inspection by an expert usually finds additional clues that help accurately diagnose a problem with mold growth on art and artifacts as well as diagnosing the probable cause of that mold; but I can say that the species of wood, in this case limewood or perhaps wood from the Linden tree. Indeed limewood has a long history of use in artworks, having been used for the carving of painted icons, apparently because of its resistance to cracking and the ease of sanding it smooth.[15]

I don't have a full picture of just what you're making or what mold you're dealing with nor its extent; so my advice is a bit general. 

In most simple terms the proper course of action is to 

1.  remove the problem mold - clean the surface; depending on the sensitivity of your wood and sculpture, simple household cleaner would perhaps suffice; for cosmetic reasons you may need to use a more aggressive or oxidizing cleaner, even bleach - but obviously you won't do that if your work would itself be damaged; 

If your work is sensitive or fragile you'll want to chat with an art conservator for some specific recommendations; often we can find success using gentle means to clean and remove stains from wood. (I am an aerobiologist interested in mold in artwork but not an expert conservator, as you'll read at some of the references in links I include below); 

2. protect the wood against new mold growth - if your project permits, when the wood is thoroughly dry, if you seal it to resist moisture uptake it will be more mold resistant.  Parmetol, a wood preservativerecommended by the manufacturer was used as a fungicidal additive to paint on the Blue Poplar wood sculpture in Amsterdam, by artist Mari Shields [per our discussion in 2010]  I'm not sure it was entirely successful. [6]

Watch out; if you don't clean adequately, or if you seal damp wood, or if your sealant is exposed to weather, there is a risk of new mold growth beneath the sealant - a condition that then could be harder to clean; I discuss this problem at  - PAINTING MISTAKES

3. identify & fix the cause of the mold growth - such as wood sculpture in a damp or wet area or if outdoors, in a shaded wet area. Those conditions need to be addresses too if you expect to avoid a recurrent mold problem on your work.

You may be surprised as well but this is not the first such request I've received from a sculptor on exactly this topic; wood is a natural meal for many species of mold. If the wood is wet and thus absorbs water the risk of mold growth is significant. Mari Shields a sculptor in Amsterdam was faced with similar problems of mold growth on a large wooden tree sculpture  that was exhibited outdoors; some of her work can be see at - and she may have other suggestions for you.

These articles may also be of interest to you

Please keep me posted on how things progress, and send along photos if you can. Such added details can help us understand what's happening and often permit some useful further comment. What we both learn may help me help someone else./P>


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