THURSDAY, SEPTEMBER 19, 2013
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.
Ever hear this one? This paint inspector walks onto a jobsite and sees a drywall surface that’s just been meticulously painted with an intermediate coat of premium high performance interior latex.
And his stomach turns: The wall looks awful, with the joints clearly visible at both the bevel joint seams and butt joints. The architect and owner are upset, and the painting contractor is pointing at the drywall contractor. The drywall contractor, however, insists that the work was done to spec.
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| Photos: MPI |
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The drywall contractor's spec may be the coating inspector's defect. |
And according to GA-214-10e “Recommended Levels of Gypsum Board Finish,” the drywall contractor is right.
That’s what the inspector faced on a large construction project for a new community center.
What to Expect from an ASTM Level 4 Finish
Here’s how it starts.
Specifiers and owners are reluctant to specify an ASTM Level 5 Drywall finish (as described in ASTM C840) because the cost goes up appreciably: Level 5 takes more time and requires greater skill (because if you don’t know how to properly apply the required skim coat, you’ll have a mess on your hands).
So the vast majority of new construction specs require an ASTM Level 4 Drywall Finish for painted surfaces, instead of the more uniform surface described by Level 5.
The Gypsum Association’s GA-214-10e “Recommended Levels of Gypsum Board Finish” is a consensus document designed to help architects and facility owners anticipate the final appearance of the wall system.
The document stipulates that an ASTM Level 4 Drywall Finish should be specified “were flat paints or light textures are to be applied” and that “paints with sheen levels other than flat…are not recommended over this level of finish.”
Looking to Lighting
The guide also suggests that joint telegraphing (also called joint photographing; it’s the defect where finished seams and joints in the drywall are clearly visible through the finish) is magnified in areas of critical lighting, which is defined as “wall and ceiling areas abutting window mullions or skylights, long hallways, or atriums with large surface areas flooded with artificial and/or natural lighting.”
The guide further warns that light striking the surface obliquely, at a very slight angle, greatly exaggerates surface irregularities.
So here’s the challenge: If the drywall contractor meets all the requirements for ASTM Level 4 finishing, with its multiple coats of joint compound over joints and angles, he will not consider surface irregularities that are visible due to critical lighting, oblique angles, or the use of a non-flat paint to be defects.
Yet that’s what they are to the paint inspector or owner who’s staring at the coated surface.
The Case of the New Gymnasium Walls
This was the case faced by the paint inspector at the handsome new community center that housed a huge gymnasium.
The gym’s 36-foot-high walls were constructed with wood paneling on the bottom eight feet, followed by eight feet of soundproofing panels. The 20 feet above the soundproofing was drywall, and these surfaces represented the perfect-storm trifecta for creating visible drywall defects:
So even though the drywall contractor had met the requirements for an ASTM Level 4 finish, the joints were telegraphing so clearly through the intermediate that from a distance of 30 feet away, the inspector—and the frustrated facility owner —could count the drywall boards.
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These joints are telegraphing so clearly through the finish that you can count the wallboards. |
To exacerbate the problem, tight scheduling demanded that a solution be found and executed quickly: All the work at 36 feet had to be finished before the gym floor could be installed, since the heavy access lifts weren’t practical for use on hardwood—and the floor installation date was fast approaching.
How to solve this?
Tips for Masking Drywall Finishing Defects
One seemingly obvious solution—troweling on more joint compound to hide the seams—is not recommended.
As we explained in our February 2012 newsletter, drywall repairs should be made only after application of the primer/sealer, and not after application of the intermediate coat. Otherwise, you’re likely to make the problem worse.
An alternative practice suggested in the GA-214-10e guide is to first apply a texture to the walls, and then apply the paint finish. These spray-applied texture products can mask the flaws in drywall so effectively that sometimes an ASTM Level 3 Drywall Finish is sufficient for painting.
However, textured finishes can quickly pick up dirt, which is undesirable in a gymnasium setting, especially at heights that create a considerable maintenance headache.
Reducing the Gloss
The most practical solution was to try reducing the gloss. So the contractor painted a test patch with the MPI Gloss Level 2 version of the specified coating; Gloss Level 2 is a high-side-sheen flat with a velvet-like finish.
To simulate the final service conditions, the contractor set up portable lights to flood the walls with the strong side lighting that would eventually pour through the windows.
Upon viewing the new finish, the inspector and owner agreed that the defects where sufficiently diminished, so the Gloss Level 2 finish was then applied on the remaining drywall surfaces. Fortunately, because a high-performance interior latex was specified, the finish’s resistance to marking and burnishing will not be significantly affected by taking the gloss level down one notch.
So what’s the moral of the story?
Anomalies and defects in new drywall finishes may be minimized by:
But in general, be warned that paints with higher sheen, or specifying the deep colors that are so trendy these days, will always tend to highlight surface imperfections.
Tagged categories: Architects; Building owners; Contractors; Drywall; Good Technical Practice; Painting Contractors; Specification; Specification writing
