Is the Problem the Paint or the Drywall?
Editor's Note: This article was written by PQA Inspector Dave Lick and is reprinted with permission from the MPI (Master Painters Institute) newsletter. MPI content describes best practices for commercial, institutional, and light industrial painting.
A patchy or uneven texture on freshly painted new drywall might seem like the painter’s fault, but it’s often actually a drywall issue, and this can lead to great frustration for both the architect and the painting contractor.
Here is a valuable lesson on why the problem occurs—and how to avoid it in the first place.
Drywall is the building material of choice for most walls these days. Consider the variance in surface textures it presents even before the painter arrives: Some surface is paper, some is sanded filler, and some is paper that was scored when the drywall contractor was sanding the filler.
The porous filler compound will soak up a latex sealer and subsequent coats of paint faster than the paper surface, causing an uneven surface appearance. The paper surfaces will raise up fibers that need to be sanded, and where the paper is sanded, it will raise up even more fibers.
But different porosity and texture is just the beginning of the nightmares that can occur when painting new drywall.
How it Happens...
Here’s how it starts: The GC or drywall contractor declares that the walls are ready for painting, and the painting contractor applies a drywall latex sealer (such as MPI #50: Primer Sealer, Latex, Interior).
However, the sealer makes flaws in the walls more visible, so the drywall finisher is called back in to touch up the deficiencies with more filler compound. The painting contractor then spot-primes by rolling more latex drywall sealer onto the newly repaired areas.
Now the painting contractor will scuff-sand the wall to clear away the fuzzy raised fibers from the drywall paper and apply the intermediate coat, generally a low-sheen eggshell or pearl finish corresponding to an MPI Gloss Level 2 or 3.
At this point, the only procedure remaining for the painting contractor should be to lightly scuff-sand the intermediate coat, and apply the finish coat.
...And What Makes it Worse
But instead, what happens time and again is that someone in power—the architect, owner, or GC—will review the surface and call for additional repairs, because new defects are now visible, including either sunken or convex seams, more scratches and popped nails.
Why are new flaws surfacing at this stage? First, the heat is finally on, which causes movement in the walls and seams; and second, good lighting is now in place that makes it easier to see the surface imperfections.
As long as the painting contractor hasn’t put the finish coat on, he’s not responsible for the defects on the surface. So in comes the drywall contractor again to repeat the process of seam repair and patching.
Now, the painting contractor will need to coat the often-sizable newly repaired areas with more sealer (another layer of MPI #50) and yet another coat of intermediate. If he is exceedingly careful, he may be able to paint only the newly repaired/sealed areas instead of re-applying intermediate to all wall surfaces.
Excessive drywall repairs over an intermediate cost will create a blotchy patchwork on the finished wall.
The wall now consists of multiple combinations of all these levels and textures:
But Wait; There's More
And it’s very likely the intermediate coat on the newly repaired areas and the original intermediate coat on the adjacent surfaces will appear different. This will give the wall a blotchy appearance, even though it’s all the same color.
The frustrated painting contractor will now lightly scuff-sand the surface and apply the coat of finish specified in the contract. When the paint dries, he thinks he’s done.
But then, the architect (or other person in power) may examine the surface and draw this conclusion: “It looks awful. Paint it again.”
Fact is, the architect will be right, because that surface is a patchwork of the varying levels of repairs and paint listed above.
The uneven surface appearance also comes from varying layers of roller application: A different texture is created every time a surface is rolled. Three coats of roller-over-roller produces a different stipple and texture than two coats of roller-over-roller, with different overlap areas that are clearly visible from a 45-degree angle and three feet away.
And that’s if the painter did a perfect job.
The weaker the craftsmanship, or the deeper the color, the more visible the variance.
'Filling' with Paint
The fact is, paint is not a filler. Conventional latex paints have a dry film thickness of just 1-2 mils.
That’s a quantity too small for most people to grasp, so consider this: A five-dollar bill is roughly the thickness of a full three-coat system. Now, picture a layer that’s just one-third the thickness of that five-dollar bill. How could it possibly mask these types of defects?
In our experience, it can take many additional coats to create an even texture or hide the flaws. A high-build coating such as an epoxy might solve the problem in one or two coats, but these are not often specified for interior drywall surfaces.
How Could This Problem Have Been Avoided?
One simple solution is for the specifier to require an ASTM Level 5 drywall finish instead of the typical Level 4.
Level 5 requires the drywall contractor to finish with a thin skimcoat of drywall joint compound over the entire wall, leaving a smooth surface free of marks and ridges. The initial cost may be higher, but the difference in the surface is dramatic.
And if the area is subject to critical lighting conditions or a semi-gloss or higher gloss finish is specified, such as on ceilings or areas where washability is important, MPI’s Architectural Painting Specification Manual requires a minimum Level 5 drywall finish.
If specifying a Level 5 finish is not possible, here’s a rule to live by: Drywall repairs should never be done after application of the intermediate coat.
They should be made only after the application of the primer sealer. Only minor repairs to small areas, such as dents or scratches from handling, should be made after the intermediate coat is applied. This practice also requires that painting occur after good lighting is installed and the heating system brings the interior temperature to 60°F or higher.
Also, sufficient time must be allowed for the drywall filler to dry out completely: Filler loaded into large seams during cold temperatures can take longer to dry than the construction schedule allows for.
Here's an acceptable degree of minor repairs after the intermediate coat is applied.
If the painting contractor believes the raw drywall is not ready for paint, he or she should tell the general contractor, point out exactly where the problems lie, and ask that the drywall contractor make the necessary repairs before the painting work starts.
Repair work is much harder to execute effectively after paint is applied; and if it’s a bad corner or seam, it won’t get any better by putting paint over it.
Finally, here’s a heads’ up for GCs in a hurry to get the job done: As this story illustrates, trying to fix flaws after the paint has been applied can be far more costly and time-consuming than taking steps to prevent the problem before it occurs.