Gypsum Wallboard Drywall Guide

Gypsum wallboard was first introduced in the 1920's, and it completed changed interior wall construction. This product is also known as drywall, or sheetrock. The name Sheetrock is a registered trademark of the U.S.Gypsum Co.

There are many advantages of drywall over the traditional plaster wall covering methods. Gypsum wallboard is applied dry, as the name drywall implies, so no moisture need be introduced to the underlying structure during construction. You also don't waste time waiting for the plaster to dry, and construction can take place even in cold, moist weather periods. Other benefits:

-Drywall is less expensive and less labor intensive to install
-Finished wall interiors are easier to paint and maintain
-Weighs significantly less than plaster, putting less stress on structures
-Greater fire resistance that plaster- perhaps it's greatest benefit of all

How Gypsum Wallboard is Made

The raw material for drywall is gypsum, a whitish-grey mineral also known as calcium sulphate. This substance, mined from the ground, contains around 20% cystallized water, by weight, which gives gypsum wallboard the fire resistance it is known for.

After being mined, then crushed and dried, the gypsum treated with a steam process called calcination, which removes much of the crystallized water. This takes about a half hour. The next step is add water and other ingredients to form Plaster of Paris (Named after a large gypsum deposit at Montmartre in Paris ). The plaster is then sandwiched between two sheets of specially treated paper to form the finished wallboard.

Drywall Sizes

Gypsum wallboard is available in many forms, but the most common is a ½ inch thick sheet, 4 feet wide by 8 feet long. Lengths run from 6 to 16 feet, but the longer non-standard sizes usually cost more per squre foot.

Available thicknesses range from ¼ inch up to 5/8 in 1/8 graduations. For residential building, the ½ inch thickness is the most commonly used. As the sheets get thicker, the resistance to fire and soundproofing characteristics increase. Thicker drywall is also less to prone to sag when installed on ceilings.

Types of Gypsum Wallboard

A few of the different types of gypsum wallboard available are listed below:

    Type X, with increased fire resistance rating
    Vapor Barrier backing types, usually backed with foil to resist moisture
    Water Resistant Core wallboard, for use in kitchens and bathrooms
    Exteror wallboard, for use in exterior ceilings, soffits and eaves

See Also:
Choosing a Drywall Primer