Geology of Everyday Things: Drywall

 Diving into the Geology behind the Material:  Drywall

Drywall Cut Open for Repair

Spoiler alert:  If you're part of the 95% of people in the United States who have drywall in their living space, you have rocks in your walls!

Moldy Drywall Needing Repair

Let’s talk about drywall, not just as a material we buy at the local Home Depot to swear at while we patch and paint, but as a product that blends geology, chemistry, and human ingenuity together.

Any homeowner or contractor will tell you, there’s a moment, usually after busting down an old sheet of drywall or carefully cutting into a wall for a repair, when they've paused to think: "What the heck is this stuff?"

That’s where I found myself this week, face-deep in dust, tearing up another wall.  This time it one was in a 1960s house that had termite damage.

Termite Damage on Wall

The drywall was brittle, held up by a patchwork of rusty nails and slightly less rusty hope. 

Pieces of Old Drywall

As I started beating it with a hammer and pulling out sections with my hands, something about the powdery crumble and debris cloud made me pause. This isn’t just building material. It’s made of rock!

Drywall Demolition

Drywall Removed

What Drywall Is Really Made Of

Older homes can be a patchwork of building eras. Some walls are lath and plaster, others are early drywall, and a few are sticks and leaves... maybe?  

When you cut into them, you’re cutting into history — layers of paint, creepy wallpaper, and untold stories. But no matter the age, most of what we call “drywall” is gypsum board: a sandwich of gypsum plaster between two sheets of paper.

Exposing Ceiling Drywall by Removing Popcorn Texture

At the heart of drywall is gypsum — a naturally occurring mineral called calcium sulfate dihydrate (CaSO₄·2H₂O). It forms in sedimentary environments, places where ancient seas or lakes slowly evaporated, leaving behind concentrated layers of minerals. Over time, these layers hardened into rock.

That soft powdery layer in your wall? It's from evaporite deposits, possibly formed millions of years ago in a prehistoric sea. 

Kinda wild.

Hanging New Drywall

 

New Drywall Hung

From Earth to Wall

Here’s the short journey from geology to your living room:

Drywall Patch on Wall

1. Gypsum is mined from surface quarries or underground deposits.

2. It’s crushed and heated to drive off water, turning it into plaster of Paris.

3. Water is re-added, it’s poured between paper sheets, and then dried and cut into panels.

4. You (or someone like me) screw it to your studs, tape the seams, and coat it with joint compound.

Simple? Sure. But behind that process is a deep connection to the Earth’s history — to evaporated seas, shifting continents, and chemical transformations.

Or... It Might Not Even Be Natural

Modern drywall doesn’t always come from mines. A lot of it — especially in North America — is made from synthetic gypsum, a byproduct of coal-fired power plants. When sulfur dioxide (a pollutant) is scrubbed from smokestacks using limestone, it reacts to form gypsum. That gypsum is chemically identical to the natural stuff and gets reused in drywall, keeping it out of landfills and cleaning up the air at the same time.

So next time you hang a panel, you might be putting up recycled pollution — and that’s a good thing.

Thinking Beyond the Walls

Working on an old house can feel like archaeology. But even in new builds, when you're working with drywall, you're handling a material shaped by deep time and modern innovation. That panel you just cut?

- It might be 300 million years old, from an ancient seabed.

- Or it might be less than a year old, born in a smokestack scrubber.

- Either way, it’s rock turned architecture — a literal wall between the past and your present.

So yeah, next time you’re hanging drywall, sanding a joint, or cursing that last screw that you just dropped on the floor… just remember: you're working with the Earth itself. Not bad for something we usually just paint over.