Quicklinks:
Definitions:
Sheetrock: ‘sheetrock’ is a registered trademark and product name from USG.
- Sheetrock is to wallboard/drywall as Kleenex is to Facial Tissues.
Drywall: Another name for Wallboard
Gypsum: A soft mineral (rock) that constitutes a large portion of plaster and wallboard. Gypsum is commonly shortened in saying as “Gyp” in field/practice, and is used as a substitution when people mean ‘wallboard’.
Cement Board: Comes in large sheets similar to wallboard, but has a different make-up of materials, and therefore different applications.
- The “board” in Cement Board is sometimes mistakenly thought of as “Wallboard”
- Cement board has greater resistance to water and moisture, and therefore is commonly used as a substitute in wet areas like showers and bathrooms.
Backer Board: Cement board is a type of backer board. Backer board gets its name for being behind (the “back”) of a material. Commonly used underneath tiles in wet locations. You will find backer boards with lots of different brand names such as Wonderboard, Hardibacker, etc. Cement Board is just one type of backer board.
Introduction:
Plaster, drywall, backerboard, cement board, wallboard… all these names can easily get confused with each other. Many are used for interior finishes, look relatively similar and have various interchangeable terms. However, all of these are different products that specialize in achieving different performance results and utilize different technology.
Plaster and Lath
Plaster is a material made from cementing compounds (gypsum and lime typically), fine aggregates (sand, perlite), and water. Most common cementing compound is portland cement.
Variations:
- Vermiculite & Perlite: Used instead of sand when a lightweight fire-resistant plaster is needed
- Keene’s Cement: Very hard plaster with a high resistance to abrasion and water penetration. Used in wet areas or where walls subject to scratching or other abuse is to be expected. Sometimes just finishing coats.
- Stucco (Portland Cement Plaster): Made from portland cement, lime, sand, and water. It is used for exterior applications where the need is for hard, water-resistant plaster. Also used sometimes as a backing for tile walls, and as the preliminary coats for Keene’s Cement.
Application
Metal Lath: Typically attached to studs and spans across the gap. Available in a variety of shapes.
- Diamond: General purpose, both flat and curved surfaces
- Rib Metal: Much more rigid, used for ceilings and solid partitions where flatness is desired.
Coatings
Plaster is applied in coats, and because it’s a more manual product, it has a desirable ‘human’ look and feel. The number of coats varies depending on desired look and cost. 3 Coats is typical.
- Scratch Coat: First coat that goes into the metal lath and wraps around the material and is bonded to it when dry.
- Brown Coat: ¼” thick – intermediate coat
- In 2 coat specifications, the Scratch and Brown coats are combined into the same coat.
- Finish Coat(s): ⅛” thick final coating
Gypsum Board Lath
AKA Gypsum Lath & Rock Lath & Wallboard Lath
Special product specifically designed for plastering over wallboard. The boards are attached to the wall and then veneer plaster is applied over the boards. This speeds up install and is a compromise of achieving a plaster look while taking advantage of the speed of wallboard install as essentially replacing the base coats.
- Veneer Plaster: This method is veneer plaster. This requires less time (money) and thinner coats than regular plaster, and can also be constructed to achieve a 1 or 2 hour fire rating.
Edge plaster and stucco work must be finished with metal pieces. Stucco requires an expansion joint every 10’-0” of where it is likely to crack such as the corners of doors and window openings.
Lath and Plaster Vs Drywall
In general gypsum drywall systems have become more common for interiors than lath and plaster work because of drywall’s lower cost and faster construction sequence. However, plaster may still be used where curved shapes or hard, abrasion-resistant surfaces are needed.
Stucco is still used for exterior applications, regardless of the surface form of the building.
Gypsum Wallboard
Gypsum Wallboard / Drywall / Sheetrock
Made of gypsum plaster core sandwiched by typically two pieces of paper. It is one of the most common methods of building partitions in residential construction since it is inexpensive and can satisfy most performance requirements such as sound and fire.
Advantages:
Low installation cost, quick and easy installation (simple tools), fire resistance, sound control, availability, versatility, ease of finishing, ease of installation around openings and other objects.
Applications
Gypsum board is typically used in ⅝” thick pieces, but other thicknesses are available and used in various situations.
- Special 1” thick board is used for shaft enclosures that come in 2’-0” widths. Sometimes called ‘shaft liner’. Installed using a “CH” or “Shaft Wall” stud.
- ¾” thick board provides a 2 hour fire rated assembly (with just one layer)
- ¼” thick used for curved surfaces and complex shapes
- Double-layer applications used when additional fire resistance is required or for extra acoustical benefits.
Special Notes
Because of its widespread use and availability, many different ‘special’ types of wallboard have been created to help deal with numerous situations. Pretty much, if you need it, you can probably find a more specific line of wallboard to help you out with the application. Some types are listed below.
- Type X : Fire rated partitions
- Foil-backed : For vapor barriers
- Backing board : Used for tile backing
- Water resistant : For bathrooms and other moist conditions (below grade)
- Abuse-resistant : High traffic areas
- Mold-resistant : Uses inorganic facings instead of paper
- Pre-decorated : Vinyl wall coverings. Speedier construction
- Fiberglass Mat : Used for exterior sheathing over studs for water-resistant barrier. Has structural implications to consider.
- Glass-Reinforced Gypsum (GRG)
- AKA Fiberglass-Reinforced, Glass-Fiber-Reinforced
- Designates a board manufactured from a high strength, high-density gypsum that is reinforced with continuous-filament glass fibers or chopped glass fibers. Used for more organic shapes and curves typically.
Edges
The edges are available with squared, tapered, and tongue and groove edges. Typically tapered is used because it allows the joint compound and tape to be done without showing a bulge in the finished surface.
Trim / Reglets
Like plaster walls, gypsum wallboards should have fabricated edging to protect it. An example is corner bead which is used for exterior corners not otherwise protected. Various profiles are available for different applications.
Reglets are flat, narrow architectural molding/strips that can have multiple uses. Use of reglets with wallboard is very common as a finishing design element in commercial spaces. Many reglets are available in different metals and colors.
Recycling and Environmental Concerns
Gypsum wallboard is used and produced in such quantities that its use has a measured impact on the environment. Developments and changes have been made to help reduce its impact:
- Since the 1950s, gypsum wallboard manufacturers have been using recycled paper for the paper backings, and also incorporated recycled newspaper into the mix.
- Half of the gypsum in the US is synthetic. This is a by-product of various manufacturing, industrial, and chemical processes.
- Disposal of old wall boards is a problem. Some manufacturers will recycle the old wallboard so long as it’s free of hazardous material (lead paint, asbestos), nails, screws, etc. However, it’s a big cost and therefore does not frequently happen. Removing the wallboard and making sure it’s free of these is not time or cost effective.
- Old wallboard can be pulverized and then worked into the ground as a soil additive. Some farmers are able to use it as a soil conditioner for various vegetables.
Framing for Wallboard
Gypsum wallboard framing for vertical construction can be either wood or metal. Wood is typically used in residential and metal typically in commercial or urban environments where the combustion and other advantages are necessary.
Framing with studs is typically done 16” or 24” OC and studs are available in a variety of shapes and lengths.
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