Painting Difficult Surfaces... the game is different but the rules are the same!!
Note from NH: This is an "article in progress". More will be added as time goes by... this topic is quicksand given the almost infinite number of surfaces and paints in the home repair world. However, I receive so many questions on these painting topics that, hopefully, you will find at least some answers here!
What is a "difficult surface"?
In most homes, they are walls and ceilings that are difficult to paint... improperly prepared wallboard, tile, plastic laminate, melamine, wallpaper... you name it! (There's a separate article on painting spray texture ceilings in the paint index!) Changing paint types... oil to latex, latex to oil, gloss or semi-gloss to flat... can present adhesion problems, too, requiring special surface preparation!
Even though some of these surfaces are not normally painted, especially hard surfaces like tile or countertops, in some situations (or uggggly colors) a coat of paint is a cost-effective way to make them look a little better, albeit less durable!
As the title of this article suggests, ALL painting follows certain rules.
1) Surface must be clean, dry, dust-free and, if possible, low-gloss (or "deglossed" chemically or by sanding).
Some paints will adhere to dusty surfaces, such as "calcimine" primers and some exterior paints. Some will also adhere to damp surfaces. This does not mean that you shouldn't remove as much dust, dirt and mildew before painting! Though there are some primers that tout their ability to cover glossy surfaces, even glass, the adhesion can be improved by roughening the surface (if possible) or using a deglossing chemical such as Wilbond, so-called "liquid sandpaper".
2) The surface must be solid and not be softened or loosened by the type of paint used! Fix all damage with appropriate compounds, fillers or caulks and thoroughly prime all questionable surfaces.
When in doubt, PRIME THE ENTIRE SURFACE!!
This is really critical, especially when changing paint types (latex to oil or visa versa) or glosses (from gloss or semi-gloss to flat). Frankly, the choice to be "lazy" will be a choice to fail! Painting over "soft" surfaces, such as water damaged drywall, may look fine for a short time but in a while will look as rotten as it did before! Do a proper wall repair, then prime and paint!
CAUTION!!! When applying oil primer to a surface other than drywall, always test the primer in an small, inconspicuous location first to be sure it doesn't react with the surface!! I once began priming some faux wood paneling and found that the surface of the paneling was a thin plastic sheet that wrinkled when the oil primer was applied! Egads! I solved the problem by using a water-based primer/sealer instead.
SPECIAL FOR WALLPAPER: Wallpaper should always be primed with a fast-drying oil primer/sealer. This prevents the latex top coat... the most likely finish coat today... from absorbing into the wallpaper and loosening it. Even with vinyl papers, the oil primer/sealer will stick better than the latex top coat.
SPECIAL FOR WALLBOARD SURFACE TEARS: Certain old types of drywall have a much thicker paper than modern drywall. When the surface of this paper is torn, it may appear to be solid but will "bubble up" on exposure to drywall compound. Trim off as much loose paper as possible and prime the torn paper with an oil primer/sealer BEFORE the first skim coat of drywall compound.
SUMMARY AND AN EXAMPLE!
Here is NH's take on one reader's troublesome walls, showing this theory in practical use...
I have a problem with the walls in my home… virtually all of them. Every time I try painting a room, the old paint comes off in sheets. Not everywhere, but in enough place to make me crazy! Is there some way I can repair these walls?
DR from Canton, CT
Painting can only be successful if the wall material to be painted will (1) allow paint to stick to it and (2) not come off the wall during the painting process!
Being sure a surface is clean, oil-free, and dry usually insures paint adhesion. Glossy surfaces will accept paint, but paint will always adhere more strongly if the surface is roughened slightly. Some paint primers, such as Zinsser 1-2-3, will stick to even glossy surfaces though most painters will lightly sand the surface anyway or apply a deglossing liquid such as Wilbond immediately prior to painting.
What may have happened to your walls? Painted surfaces that have been exposed to moisture or were not properly prepared prior to the LAST coat of paint may loosen when the new paint is applied, even though the painted surface appears to be totally sound! This is one drawback in using water-based paints… you often have no idea the surface is bad until you start to roll the paint on and it begins to lift off the wall… onto your roller!
If this happens… IMMEDIATELY STOP PAINTING. Continuing will only make the situation worse! Use a sponge or towels and wipe the fresh paint off the walls and let the wall dry thoroughly. Now that you know you have a problem wall, there are easy steps you can take to lessen the damage.
Once dry, scrape any loose paint from the wall. Second, in order to prevent the moisture in the latex finish paint from lifting more of the old paint, apply a full coat of an oil-based primer-sealer. I use either Kilz or the new Zinsser Odorless Primer-Sealer. The Kilz is superior if there is lots of water staining or you need a one-hour drying time. Otherwise, the Zinsser product is fine with its two-hour drying time.
The principle is simple. By sealing the entire wall with the primer, you prevent moisture from touching the old paint surface and can subsequently apply latex paints without any problems. By the way, this same technique is useful for painting over wallpaper.
You might say… what about the rough spots on the wall where the paint lifted? Shouldn't I repair them before priming the walls?
NO… if you apply drywall compound onto the walls to level them without priming first, the moisture in the compound will most likely cause more paint lifting! Seal the walls first… then apply the patching compound. Once you have applied, sanded, applied again, sanded again, etc. and the walls are smooth, spot prime all the repaired areas. If they are extensive, reprime all the walls again! Then and only then are you ready to apply a full coat or two of quality latex wall paint.
And don't forget to prime ALL the walls and even the ceiling. Murphy's Law says that if anything can go wrong, it will. If you have one bad wall, odds are all the walls and the ceiling in that room are in questionable shape!
More special painting issues and questions...
Can I paint over contact paper? I really don't want to try to strip it unless I absolutely have to.
Painting over any glued-on coating, whether it is contact paper or wallpaper, is not my first preference. But I "feel your pain" and know that once you start trying to strip it, you are committed to what may be a humongous project!
Contact paper can be painted over but an appropriate primer must be used. Ordinary oil or latex paints will not stick very well, so a quality primer-sealer is essential for a long-lasting job and an eminently paintable surface! One consideration in your choice of primer is its chemical makeup… you have to be careful not to use a paint that will chemically react with the plastic or seep into the seams and dissolve the glue! We do not want to make more work for ourselves! My suggestion is to first use a water-based stain killing primer, available at any hardware or paint store. These chemical wonders are designed to stick to virtually any clean surface, giving you that "eminently paintable surface"! Glass, glossy paints and even plastic laminate countertops and cabinets are all within its scope!
Be sure to clean the contact paper before painting especially if you think there might be any oil or grease on it. Don't spare the elbow grease… even these special primers will fail if painted over dust, dirt or oils. Use any cleaner you want that is safe for contact paper... just thoroughly rinse and dry the contact paper before priming.
A last note… don't under any circumstances use sandpaper to roughen the surface. The abrasions you cause might make the surface visibly rough. You could even tear the contact paper!