Gypsum drywall has largely displaced traditional plastering for interior walls and ceilings. Many homeowners are surprised to discover that the vast majority of the gypsum used for drywall is the waste byproduct of coal-fired power plants pollution control systems. This is in contrast to gypsum, lime and other plaster binder materials that are mined from naturally occurring deposits. I would like to highlight a few specifications where traditional plasters should be considered as a practical alternative to drywall:
- Monolithic substrates
- Curvilinear surfaces
- High durability
Cast Mouldings and Ornament
As the millwork industry became increasingly sophisticated, soft “paint grade” woods such as pine and poplar began to displace plaster as the economic plain moulding specification. The integration of ornament enrichment into mouldings slowed this transition until ornament itself was largely stripped from architectural design in the mid-20th century. Nevertheless, there are many strong arguments for specifying plaster mouldings with the following specifications often being competitive or less expensive:
- Medium to large curvilinear profiles
- Non-radial curvilinear profiles
- Large, complex crown mouldings
- Curvilinear oriented mouldings
- Low maintenance
Particularly when large or ornate mouldings are specified I have found clients concerned about maintenance becoming an issue. The coefficient of expansion of soft woods is relatively high with changes of temperature and especially humidity. This is exacerbated by the reality that wood mouldings are typically affixed mechanically against drywall or plaster materials that have a very low coefficient of expansion. The wood moulding moves, the wall does not and cracks develop quickly between the disparate materials that are either addressed with caulk or lived with. Alternatively, plaster mouldings are affixed with plaster to a plaster (or drywall) substrate. The result is a monolithic system, the bond is so strong that the mouldings literally become a part of the wall. Most plasterers will guarantee that aside from structural movement their work will not crack, ever.
This article is a brief summary of a subject that can become very specific for a given project. As a technical consultant for plaster materials and application, I provide services to architects helping them properly specify plaster and plaster systems. I also work with plaster contractors providing training and onsite consultation services as needed.
Contributed by Patrick Webb