Finishing Tapered Edges; BIM
Lee G. Jones / February 2015
Q: When applying gypsum wallboard to areas that will either go undecorated or covered with wallcovering (i.e., unpainted), is there any reason to worry about which side of the board is facing out (or facing into the wall cavity)?
A: One reason to be mindful that the front of the board faces out is that the edges of some gypsum panel products, particularly gypsum wallboard, are tapered. The taper on the long edge of the board, when butted up against another tapered board edge, creates a hollow area or depression in the surface that will be built up to level when tape and joint compound are applied (and taping over joints without tapered edges invariably results in a visible buildup of material). If boards with tapered edges are applied with the back sides facing out, there will be a space between face of the tapered edge and the framing. If the fasteners applied along the tapered edge are installed tight enough to ensure complete contact with the framing, the board may crack, and if the fasteners are not driven all the way in, the movement of the building may result in the board coming loose around the edges or the fasteners being worked loose from the framing, or both. If it is absolutely necessary to install the board face-in (I struggle to come up with a reason for this, but I’m sure the situation may come up), the tapered edges can be cut away from the panel to create squared edges (and narrower panels), which will prevent creating the gap or cracking that would otherwise occur. Panels modified this way should be attached with the long dimension perpendicular to the framing to avoid creating joints that are unsupported by framing, now that the spacing of the boards and the framing no longer have a commonly divisible width.
In cases where wallcovering is the final finish, there are many variables to consider, foremost of which is the weight (thickness) and texture of the wallcovering. Unless the wallcovering is a really heavy (thick) and highly textured material, it is not likely to hide unfinished joints, so the tapered edges need to be facing out and the joints finished to a level appropriate for the wallcovering being used. In many cases, this will be a Level 4 (tape embedded in joint compound and two more coats of compound to achieve as flat a surface as possible) because there is enough of a sheen on the surface of the wallcovering to highlight surface imperfections, and many wallcovering are not thick enough to hide surface irregularities. GA-214 recommends at least a Level 3 finish (tape embedded in joint compound and another coat of compound applied separately over the tape) under heavy textured wallcoverings, so the likelihood of obscuring the irregularities found on a wall created with back-side-out gypsum board using wallcovering is less than favorable.
Q: We have shied away from jobs that require BIM, but we’re seeing more jobs that ask for it. What are some of the pros and cons of getting into BIM that we should know about?
A: Building Information Modeling, better known as BIM, is a powerful design tool that potentially all but eliminates cost overruns, rework and delays on construction projects. It has been and continues to be a topic of discussion among AWCI members, to the point of being the highlight of the general session at our 2014 fall conference and is slated to be the next subject in our Doing It Right educational series. While following several of the discussions and reading several documents about the pros and cons of getting into BIM, I’ve gleaned several points to consider.
First the pros (and this is by no means a complete list): Using BIM facilitates extremely accurate job estimates, and it is flexible enough to automatically calculate changes in material quantities as necessary when a building system is altered within a design. It provides the ability to avoid clashes between trades so that plumbing, HVAC, ceilings, framing, etc., do not inadvertently wind up trying to occupy the same space, which in turn avoids the rework, delays and associated costs that sometimes occur when using other design tools. BIM can be used calculate energy efficiency, lighting requirements, acoustical properties and life cycle costs on different virtual designs for comparison purposes. BIM can also analyze designs to ensure they are code compliant, which speeds up the permit process. Buildings designed using BIM provide building owners with complete, comprehensive records that eliminate guesswork when maintenance, alterations or upgrades need to be made for the life of the building.
And some of the cons: As with any computer program, the quality of the final calculations is totally contingent on the quality of the data input, or “garbage in, garbage out,” and the learning curve may be quite steep. There are several competing BIM packages and they don’t in all cases communicate directly, so comparing designs using different packages may involve another program to ensure the desired result. Perhaps most important, buying and using a BIM system is not cheap (the number offered at the presentation in Baltimore was about $109,000 a year).
The Foundation of the Wall and Ceiling Industry has on online white paper that goes into great detail on these points, which can be found online at www.awci.org/pdf/bim.pdf. In this document, it sets the breakpoint for whether a firm with 100 or more employees can afford to purchase a BIM system. However, smaller contractors can hire design firms with BIM capability to get into the game.
Lee G. Jones is AWCI’s director of technical services.