I find references to "SW edge" ('SW' being 'smooth wall') in USG literature. Ex (link),
SHEETROCK Brand Gypsum Panels, SW Have an exclusive tapered rounded
edge design to help minimize ridging or beading and other joint
imperfections. This edge produces a much stronger joint than regular
tapered edge when pre-filled with DURABOND setting type compound and
finished with joint treatment. Except for the rounded edge, panels
are tapered like, and otherwise identical to, regular tapered-edge
gypsum panels.
I got curious because the USG Gypsum Construction Handbook ch 5, "Joint Treatment for Drywall Construction" says, (bold added)
Prefilling Joints is desirable when there are large gaps between
panels. This step is necessary with SW edge board.Fill the “V” groove between Sheetrock brand gypsum panels, SW (see
diagram), with joint compound such as Sheetrock brand setting-type
(Durabond 45 or 90) or lightweight setting-type (Easy Sand 45 or 90). …
However, I don't find (or don't understand) any references to "SW" in what I think is the USG panel products list. Everything there seems to be either 'tapered' or 'square' edged.
This makes me wonder whether 'SW Edge' is a product per se, or just the name USG uses for all its tapered edges.
… And, if the latter, is it necessary (per the Handbook, above) to pre-fill the taper with Durabond/EasySand.
Best Answer
The "SW edge" panels are a subtype of tapered edge panel. The USG panel products list link refers to a product performance brochure concerned only with the fire, mold, moisture, sag, abuse, impact, and shear resistance regarding the entire panel.
USG offers panels with a square edge only as a base panel, which is usually intended to be covered in its entirety with gypsum/plaster and sanded to a finish, or another layer of gypsum board.
USG also offers panels with tapered edges, in both the "conventional" and "SW edge." If you intend to meet the USG spec, this means it is necessary to pre-fill the "SW edge" taper with Durabond/EasySand.