What Is Drywall Made Of?

Attic With New Drywall
Attic with New Drywall. Getty / Banks Photos

When the problems of Chinese-made drywall were publicized, for many homeowners it provoked the larger question:  What is my drywall made of?  And how about the joint compound that is used to create seams between the drywall slabs?

Rock and Paper Game

After years of technological wizardry and product development, it is interesting to note that our walls are still essentially made of two simple materials:  rock and paper.

 

While drywall will have a number of additives, most companies manufacture their product from:

  • Gypsum:  Comprising between 70% to 90% of sheet drywall, gypsum has long been the mainstay of drywall products.  Otherwise known as calcium sulfate, gypsum is cheap to mine, fire-proof, and provides superior sound-deadening properties.  Fire-rated type X drywall will have fiberglass added to the gypsum.  Unlike asbestos, which is known to cause an often-fatal illness called mesothelioma, gypsum dust is not a grave health hazard.  
  • Cellulose:  Up to 10% of drywall's composition.  Cellulose is the paper facing on both sides of the drywall.  Increasingly, though, drywall is being faced not in paper but in mold resistant fiberglass mat.  Examples include USG Sheetrock® Mold Tough and GP's DensArmor Plus®.  In fact, if you ever use a paper substitute tape such as FibaTape, you are using the same type of material used for mold-resistant drywall.

    After those two majority materials, everything else is in trace amounts:

    • Crystalline Silica
    • Vermiculite
    • Potassium Sulfate
    • Starch
    • Mica
    • Wax
    • Boric Acid

    Joint Compound Composition

    Because the joint compound, or mud, for covering up the tape joints between sheets of drywall looks like gypsum, it's often assumed to be gypsum.

     It's not.

    • Calcium Carbonate:  Otherwise known as ground limestone, this is the main mineral in drywall mud.  
    • Talcum:  Is drywall dust the bane of your remodeling existence?  Are you continually taping up barriers to prevent dust from reaching other parts of your house?  Well, blame talcum.  This ultra-fine mineral, familiar as baby powder, is used in joint compound because its platy particles lie flat and resist cracking.  Talc is the element that helps your mud sand down as smooth as glass.  Between 5% and 15% of joint compound is made up of talc.

    Sulfur and Strontium Are Not Welcome

    Sulfur was found in Chinese drywall, but none in U.S.-made drywall. Strontium was found in much higher concentrations in the Chinese drywall than in the U.S. drywall.

    Acetaldehyde and formaldehyde were found in both Chinese and U.S. drywall. But in the U.S. drywall, these substances were within safe limits (and not in the Chinese drywall).

    U.S. Brands of Drywall Are Clear

    Sheetrock® brand wallboard, made by USG Corporation, is the most famous type of drywall. If you have wallboard from USG, you can be assured that no "Chinese-type" problems will develop with you wallboard. USG reports that in 90 years of manufacturing, its products have experienced none of the same problems as found in Chinese drywall.

    If that doesn't reassure you, when we spoke to USG, they told us that "USG’s Sheetrock® brand wallboard is made in North America. USG has never manufactured wallboard in China and never relabeled or rebranded wallboard manufactured in China."

    In a joint study from the U.S. Consumer Product Safety Commission and four other U.S. federal agencies, U.S.-made drywall was not found to have issues similar to Chinese drywall.