Seems like when we get one problem solved and another problem crops up to take its place. There has been a lot of interest lately in drywall primers. I am aware of the activity by the Drywall Finishing Council in California. Darin Coats and Michael Logue are developing language for ASTM C840, Standard Specification for Application and Finishing of Gypsum Board, to clearly define the primer to be used on gypsum board. Currently C840 says the following in Article 23 – Decoration:
23.1 Surfaces finished to Levels 3, 4, or 5 shall be covered with a drywall primer compatible with the final decoration prior to the application of the final decoration.
NOTE 16—It is not the intent of this specification to assign responsibility for performance to specific trades.
And the following is offered in Appendix X3:
X3.3 Because the porosity and texture of the gypsum board differs from that of the joint treatment, the surface shall be primed and sealed as may be required for the subsequent finish coats.
Darin and Michael are working with the Painting and Decorating Contractors of America and the Master Painters Institute to ensure that these two organizations endorse the proposed language needed to change C840. This joint effort will only make the painting industry aware of the problems caused by the use of an improper primer.
When we look at Appendix X3, the statement “The surface shall be primed and sealed” is used. There is no definition for primer or sealer in C11, Standard Terminology Relating to Gypsum and Related Building Materials and Systems, or C840. So C840 needs, at the very least, a clear definition of these two terms as a start.
There is a lack of knowledge in the design side of the industry about just what the composition of a drywall primer should be. Not being a paint specialist, I am not completely sure either. I do know that it is recommended that the primer have a high solids content. This component of the primer helps to fill in the difference between the joint compound and the face paper of the board as recognized by the information contained in Appendix X3 of ASTM C840, thereby producing a smoother finish and reducing the potential of telegraphing of joints through the finish coat of paint. Article 23 of C840 also recognizes that there is an issue with the composition of paints used over drywall.
Another problem that the use of the proper primer will correct is when ready-mixed and setting-type joint compounds are used on the same section of wall. I have received several calls trying to discover why the paint is peeling off the walls. In both instances the finisher used setting-type compound in the final coat of joint compound in random locations while, for the most part, also using ready-mixed joint compound in other locations on the same run of wall. Since setting-type joint compound uses a chemical additive to accelerate the drying process, there is a reaction with the primer that is different from the reaction you’d get by using a combination of primer and ready-mixed joint compound. In other words. the primer does not adhere to the surface of the gypsum board and subsequently fails. This is only a problem if the painter is not aware that two different types of joint compound were used on the same run of wall. Some of the contractors I have talked to have found painters very receptive to information that helps them produce a quality job.
I believe that a contributing factor to this problem is how we as an industry draw the lines for responsibility of the performance of work. Depending on the location of the project, these lines of responsibility change primarily due to labor agreements and custom. The accepted rule in the industry is that if you start your work, you have accepted the underlying as being in a condition that will not cause future problems with or affect the quality of your work.
So what solutions other than making a change to the ASTM standards are available? One path is to educate the design community about the important of selecting the correct primer for the substrate. However, if you find that on a project you have to use a setting-type joint compound in order to speed up the finishing the project, it then becomes incumbent on you to notify the painter of the locations where it was used so the painter can change the primer if needed. You also need to look at the painting specification to ascertain if the proper primer was specified.
Donald E. Smith, CCS, is AWCI’s director of technical services. Send your questions to firstname.lastname@example.org or call him directly at (703) 538.1611.