You're right, generally speaking, there's very little space directly behind drywall (gypsum board, or "gyp board"). Here's a breakdown: Drywall Thickness

Drywall typically comes in 1/2 inch or 5/8 inch thickness.

Standard Wall Construction

Drywall is typically attached directly to studs (vertical framing members) or furring strips, which are attached to a wall.

Why Space is Limited



Direct Attachment

The goal is to create a flat, solid wall surface. So, drywall is fastened as closely as possible to the framing.

Insulation

Sometimes, insulation (like fiberglass batts) is placed between the studs, which further minimizes the space.

Scenarios Where You Might Have Space (and boxes)



Existing Boxes

Electrical outlets, switches, or data ports are typically mounted in electrical boxes that are screwed into the studs before drywall is installed. The front edge of the box is usually flush with the finished wall surface. If you're talking about adding a box behind the drywall, that's unusual.

Furling Strips

Sometimes, instead of studs, narrow strips of wood (furring) are attached to the wall. This might create a very small gap (perhaps 1/2 inch or less) between the original wall and the back of the drywall. However, it's not a practical or safe space to put an electrical box.

Chase Walls

Very rarely, a "chase wall" is built to hide plumbing or ductwork. This could create a larger cavity. But this is uncommon in most residential construction.

Drop Ceilings

If you're referring to the space above a drop ceiling, then yes, there's often plenty of room for boxes and other equipment. But that's not typically "behind" the gyp board in the typical wall sense.

Why it's generally not done



Code Violations

Burying electrical boxes behind the drywall is a major fire hazard and a violation of electrical codes. Electrical boxes need to be accessible for maintenance and safety.

Structural Integrity

Leaving a significant gap behind the drywall could compromise the wall's structural integrity.

Wiring Access

Wiring is designed to be routed within the wall cavity, not behind the finished surface.

In conclusion

It's not feasible or safe to have a box "behind" the drywall in most situations. Electrical boxes are mounted within* the wall framing, with the front edge flush with the finished wall surface. If you need to add an outlet or other electrical component, the proper way is to:1.

Identify an existing circuit

Ensure it has sufficient capacity for the new load.2.

Run new wiring

From the existing circuit to the location where you want the new box.3.

Install a new electrical box

Securely attach it to a stud, with the front edge flush with the drywall.4.

Connect the wiring

Following all electrical codes and safety precautions.

Important Safety Note: If you're not comfortable working with electricity, it's always best to hire a qualified electrician. Flag for review