Is Insulated Plasterboard Fireproof?

Many might think that drywall and plasterboard are the same things, but they’re actually not. So while drywall is relatively fire-resistant, what does that mean for plasterboard? Would insulated plasterboard be fire-resistant, or fireproof, as well?

Insulated plasterboard, while not entirely fireproof, is indeed fire-resistant. There are many components of the board that can play a part in this, such as the elements of the core. Overall, insulated plasterboard can last about 45 minutes in extreme temperatures.

While insulated plasterboard can be fire resistant in general, it’s important to know what exactly helps to make it so and how effective it can be. Below you will find a little more about what insulated plasterboard is, how it will hold up in a fire, and different things that can add to its ability to resist fire.

Plasterboard: What Is It?

To know what plasterboard is, first you need to know what drywall is.

Drywall is basically a panel made of two paperboards that have a material known as gypsum sandwiched in the middle. It can have other materials inside of it as well. Drywall is typically used as a part of the construction of interior walls and ceilings.

Now, plasterboard isn’t all that different from drywall, but it is not the same. Rather, plasterboard is a type of drywall. It’s wallboard with a gypsum plaster at its core and bonded to different layers of fiberboard or paper. It’s used in place of plaster and other types of wallboards in the process of making interior walls.

The only real difference between regular plasterboard and insulated plasterboard is that insulated plasterboard is made of a sheet of standard plasterboard and a sheet of insulating material put together to make one board.


I’ve mentioned gypsum previously in this article, but haven’t exactly covered what it is. Gypsum is an essential part of plasterboards and the cause for much of the fire resistance that insulated plasterboards have.

Gypsum is a white or gray mineral mainly consisting of a chemical compound known as calcium sulfate dehydrate. It is used to make many kinds of plasters (such as Plaster of Paris) and is used a great deal in various parts of the building industry.

It is mostly fire-resistant because of the glass fiber reinforcement and other additives that it has inside of it. Gypsum traps water molecules inside of its material and this also helps hold off heat from fully damaging any walls as quickly. It takes rather high temperatures to burn through gypsum.


Another element that can play a big part in making fire-resistant insulated plasterboards is polystyrene. Polystyrene is a synthetic resin used for lightweight, but rigid, foams and films. As an example, styrofoam is basically just an expanded version of it.

Polystyrene is very commonly used on insulated plasterboards. An important thing to note about this material though is that it does have rather high levels of toxins. They’re not naturally dangerous, especially when under normal temperatures, so it’s okay you don’t have to be worried about it. If, however, the insulated plasterboard catches fire, that can cause a problem once the polystyrene is subjected to extreme heat.

After polystyrene has been under high heat for a little while, the toxins will start to emit into the space around them. Polystyrene doesn’t smell pleasant at all when it burns so you will probably be able to tell when it is being released. If you are not a safe distance away when the toxins start to come out, that, combined with the smoke from the fire, can enter your lungs and cause a lot of gagging and choking.

If enough toxins from polystyrene are inhaled, it can be deadly for any human being.

Another substance to take note of in insulated plasterboards is polyisocyanurate. Keep in mind this is not the same as polystyrene. Polyisocyanurate is a thermoset plastic produced as a foam usually and used in a lot of thermal insulation. Your plasterboards will probably have it, but it is not fire-resistant. It is actually a combustible material but is not toxic in any way.

Types Of Insulated Plasterboard

There is more than one type of insulated plasterboard. The type of board you have will probably affect the amount of fire resistance of the board. Here are some types of insulation plasterboards:

  • Basic Insulated Plasterboard: This type of plasterboard is, as the name suggests, the simplest of thermal plasterboards. It is typically a 9.5 mm gypsum board, basically an expanded sheet of polystyrene, and is one of the cheaper boards used for installation. It’s usually used for lining interior walls.
  • Vapor-Control Insulated Plasterboard: This type of board is usually a bit thicker, around 13 mm, and backed with polyisocyanurate foam. It will also include a couple of layers of vapor control material.
  • Moisture Resistant Insulated Plasterboard: This one is about as thick as vapor-control boards, backed with rigid polyisocyanurate foam and two vapor barriers. This is helpful for lining walls where good thermal and moisture resistance is needed.
  • High-Performance Insulated Plasterboard: This board can vary anywhere from 9 to 13 mm and is backed with something known as phenolic foam. It may or may not also have a vapor-control layer. It’s used both for walls and ceilings for insulation. Source

How Will It Hold Up In A Fire?:

First of all, it’s important to remember that insulated plasterboard does have a great deal of wood and paper in it so that will eventually burn if exposed to fire.

Typical plasterboard resists fire for about 30 minutes, so insulated plasterboard should hold up for at least a little longer than that. Since it’s insulated, it should be able to hold up to heat a little better.

Plasterboard is actually more fire-resistant than drywall. The paper itself will burn easily, but the gypsum inside of the plasterboard is much harder to burn through.

Take into consideration that fire resistance will depend on more than the type of insulated plasterboard you have, but also the framework, partition, and thickness of the wall as well.

Ricky Kesler

With all of the projects I've done over the years, you'd think that I work on my house full-time. But I actually enjoy other things like spending time outdoors and time with my family.

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