Q: The question this month involves the levels of finishes for drywall. The caller, an architect, said the owner had required a Level 5 Finish on the corridor walls of a school. Apparently the Level 5 was required due to a semi-gloss paint. The contractor wanted to know if a textured finish qualified as a No. 5 Level finish in this case.
A: The levels of finish of gypsum board is covered in several publications. The basis for all of these publications is ASTM C840-04, Standard Specification for Application and Finishing of Gypsum Board, published by the American Society for Testing and Materials.
The terminology section defines skim coat as “a thin coat of skim coat compound applied over the finished wallboard surface.” Section 22, “Finishing of Gypsum Wallboard,” addresses the preparation and materials used for finishing. Section 22.6, “Levels of Finish,” describes the five levels of finish. Of interest in this situation is Level 5. ASTM C840 reads as follows: “22.6.6.1 All joints and interior angles shall have tape embedded in joint compound and shall be immediately wiped with a joint knife or trowel leaving a thin coating of joint compound over all joints and interior angles. Two separate coats of joint compound shall be applied over all flat joints. One separate coat of joint compound shall be applied over interior angles. Fastener heads and accessories shall be covered with three separate coats of joint compound. A thin skim coat of joint compound shall be trowel-applied to the entire surface. Excess compound is immediately sheared off, leaving a film of skim coat compound completely covering the paper. As an alternate to a skim coat, a material manufactured especially for this purpose shall be applied. The surface shall be smooth and free of toll marks and ridges (see 22.4.1.1).”
The sentences in italics clearly indicate that the intention is to provide a smooth surface. This would preclude using a textured surface as textured surfaces by their nature are not smooth.
The appendixes provide additional information that includes the appropriate use of each level of finish specified. They also help us understand the reasoning behind establishing levels of finish for gypsum wallboard.
Why specify levels? The reasons are as follows: (1) many building are designed with walls and partitions abutting window mullions, long hallways or atriums with large surface areas flooded with artificial and natural lighting; (2) paints and painting methods have changed over the years with wider use of spray equipment and reduce solids in paint; and (3) differences in absorption and drying, shrinkage of the compound, tool marks and ridges in the compound, or scuffing or raising of the nap of the face paper may all, or in part, combine to emphasize visual differences.
It is recommended that the painting specification provide for proper treatment to ensure uniform absorption over the entire surface. Any special finish such as gloss, which demands a more stringent requirement than the standard surface provides, should be specifically pointed out in the design process.
A Level 5 finish is not a substitute for plaster. There is a substantial premium to be paid for a Level 5 finish. Personally, I question the use of this level of finish in a school corridor due primarily to the potential abuse. True, a semi-gloss paint was being used; however, in my experience, the walls are repainted more often than they are scrubbed down. And there are alternative materialso available at a savings that can be applied over a Level 4 finish to produce a Level 5.
Finally, standards contain a tremendous amount of information that can prevent problems in the field.
About the Author
Donald E. Smith, CCS, is AWCI’s director of technical services. Send your technical questions to him at [email protected], or fax them to (703) 534–8307.
