The term ‘drywall’ is so ubiquitous in the construction industry it’s reasonable to ask if a ‘wet wall’ was ever a counterpart term.
‘Drywall’ is a term referring a board material with a gypsum-based core, and like all building materials and methods needs to be understood in the context of efficiency (i.e. cost savings). While material costs and scarcity have sometimes led to new products (particularly in the wood industry with the development of thin veneers, plywood, OSB, etc.), the largest portion of construction costs is almost always labor. Reducing labor (skilled or otherwise) means reducing cost.
Prior to its development in the early 20th century, wall finishes were commonly constructed of lath and plaster – a wet-applied product built up in successive layers to create a smooth, hard finish.
This process would traditionally begin with a base coat applied over wood lath (strips of wood fastened directly to wall framing). When applied, some plaster would be forced through the gaps in the lath creating a mechanical attachment – referred to as ‘keys’ – so this coat is often referred to as the ‘key coat’, or a ‘scratch coat’ referring to a roughening of the surface to allow the next coat to adhere. Over this would be applied a second layer or ’brown coat’ that would provide a smooth base for the final, thinner ‘white coat’. This would ultimately result in a smooth, flat, and hard finish.
Plaster ‘keys’ seen from behind © Erin Alexis Randolph
This was a highly durable finish – though anyone who has owned a historic house can attest that a common problem is the ‘keys’ from the key coat dislodging, and since this is the only thing holding the finish in place, loose plaster was often the result.
It is also a highly skilled, labor-intensive process. Assuming the framing and lath are installed flat, building up those layers with a trowel into a flat, consistent finish at least 3/4″ thick required tremendous skill. A significant benefit of these systems was also their ability to ‘level out’ uneven framing (an issue particularly noticeable in older construction where rough timbers were often used).
Eventually wood lath was replaced by small gypsum panels — commonly called rock lath or button board — faced with paper and often perforated with holes that allowed plaster to key mechanically into the board. While gypsum wallboard was promoted as a ‘finished product’ as early as 1916, it was initially resisted by homeowners (perceiving it as ‘cheap and shoddy’) and labor unions seeking to protect members.
Perceptions changed around WWII and the postwar housing boom ushered in widespread use of ‘gypsum wallboard’ and the decline of plaster (by the 1980s 90% of residential construction used drywall instead of plaster).
What gypsum wallboard lacks in durability (gypsum is both a very soft and water-soluble material) it makes up for with ease and speed of installation. The only finishing typically required is taping and ‘plastering’ seams with joint compound, and then paint. The gypsum industry has tried to deal with a number of shortcomings with specialized boards that are ‘moisture-tolerant’ and ‘abuse-resistant’ which typically modify the facing layers.
‘Finishing levels’ from 0 – 5 have also been defined, with 0 being unfinished boards and 5 having a thin layer of joint compound skimmed over the entire surface (skim coat), and the intermediate layers involving degrees of finish on joints and screw heads. However, even with a Level 5 finish, grazing light will reveal panel joints.
Typical finished drywall surfaces ready for paint © Pramot Pantadet
Modern construction materials and techniques have therefore made wet plaster systems unnecessary, and aside from improved acoustics, there is little benefit to traditional plaster walls that are painted. However, due to the understanding of wet plaster as a difficult (and costly) material to work with, it is often perceived as a ‘high-end’ material. In response to this, veneer plaster systems were developed to deliver that aesthetic at a more accessible price point.
Similar to historic wet plaster systems, this consists of a single layer typically 1-3mm thick applied over chemically treated gypsum-based boards. While this is less labor-intensive than fully wet 3 coat systems, and offers the benefits of a smooth seamless installation with comparable appearance, the labor and skill involved (and associated costs) makes it less feasible for most projects.
