Fire rating for sheetrock: Basics of Fire-Rated Type X or C Drywall

Basics of Fire-Rated Type X or C Drywall

When you are installing drywall, building code often dictates the types of drywall that must be used. One type of drywall that shows up in building codes is Type X or Type C drywall or fire-rated drywall.

While beneficial, fire-rated drywall is often given more attributes than it truly has. This drywall is fire-rated but not fireproof. While it will slow down the passage of fire, it will not stop it. Type X or Type C drywall is only one of many methods homeowners should use to stay safe in the event of a home fire. In fact, fire ratings for Type X or C drywall can be a bit deceptive because they refer to full, complete wall system, not just the drywall.

Fire-Rated Type X or C Drywall

Fire-rated drywall is drywall that is thicker than standard sheets and which sometimes comes with extra additives to the gypsum core such as fiberglass. The purpose of fire-rated drywall is to slow the progress of fire to give inhabitants enough time to escape.

What Is Fire-Rated Type X Drywall?

Fireproof drywall is the common term; its industry name is Type X drywall. The thickness of this drywall is 5/8-inch, including all layers.

Glass fibers are added to the board to help it slow down the fire. Also, because it is denser than normal gypsum and paper drywall, it takes longer for the fire to degrade it.

Most Type X drywall has a one-hour fire rating. The fire rating for the 1/2-inch drywall used throughout the rest of the home is 30 minutes.

As an added benefit, Type X drywall absorbs sound slightly better and is slightly stronger than conventional 3/8-inch or 1/2-inch drywall.

Type X vs. Type C Drywall

Both Type X and Type C drywall are rated as fire-resistant materials. Both have 60-minute wall system ratings.

Type C has more additives to the gypsum core that make it slightly more fire-resistant than Type X drywall.

Why Fireproof Drywall Is Fire-Rated

Type X or C drywall is by no means 100-percent fireproof. Simply it is drywall that will stand up against flame longer than regular drywall.

Also, just because an area is covered in Type X or C drywall does not ensure fire safety for that area, since fire can still find other pathways, such as vents, doors, gaps, cracks, and unblocked stud wall assemblies.

If a conventional 1/2-inch thick sheet of drywall will stand up to 30 minutes of fire, then the added 1/8-inch found in the Type X or C drywall, along with its other properties, will double your margin of safety to 60 minutes. For this reason, fire-rated drywall is sometimes called one-hour fire wallboard.

Fire-Rated Drywall

Termed Type X or Type C

5/8-inch thick

Rated to 60 minutes

Embedded with glass fibers

Required by many building codes

Rating backed on assembly systems, not just the drywall alone

Where to Install Type X or C Drywall

In residences, fire-rated drywall is typically required by building codes to be installed in a few of these places:

  • Near furnace and utility rooms
  • Places where a wood stove is used
  • Garages and especially the garage walls that separate that area from the main house
  • Garage ceilings that have living areas above

Should You Install Type X or C Drywall Everywhere?

No, fire-rated drywall is not intended to be installed in all areas of the home.

Fire-rated drywall tends to run about 20-percent more expensive than conventional drywall panels. While this is not much on the small scale, it can represent a substantial cost difference when multiplied across an entire home’s worth of drywall.

More importantly, the fire will find any number of easier passages to travel than through drywall. For example, if a bathroom, nursery, bedroom, or home office were hung with Type X or C drywall, the fire would readily move through oxygen-rich open doors and hollow-core doors long before attempting to burn through the drywall.

If you want fire-rated drywall to be installed throughout your house, you would need to request this with the contractor, as this is not normally done.

Type X or C Drywall Testing Limitations

The ability of Type X or C has less to do with the actual drywall sheet and more to do with the entire wall system as a whole: all items included such as studs and insulation.

USG, the manufacturer of Sheetrock Brand Firecode C Gypsum Panels, makes the point that ASTM (American Society For Testing and Materials) testing of fire-rated drywall requires that entire “assembly/systems” be tested, not just the drywall.

Because these assemblies are composed of many different parts, any of which could affect results, these results may be skewed. USG notes:

This simply means that for a ‘one-hour fire rating’ of a gypsum board assembly/system, all requirements of an ASTM E 119 test were successfully met in a testing laboratory furnace for at least 59 minutes and 30 seconds for that specific assembly/system and with those specific components of the assembly/system.

Thickness and Composition

Drywall typically comes in 1/4-inch, 3/8-inch, and 1/2-inch thicknesses. Type X or C drywall is 5/8 inches thick.

In addition to the usual gypsum found in regular drywall, fire-rated drywall contains glass fibers to form a super-tough core. The gypsum and fiberglass are packed tighter and denser than with regular drywall.

Cost and Availability

Fire-rated drywall costs more than regular drywall. As a rule of thumb, you can count on it costing about 10-percent to 20-percent more than conventional drywall of the closest possible thickness.

Type X or C fire-rated drywall is not a specialty product. It is available at local home improvement stores or contractors’ supply houses.

Do I Need Fire-Rated Drywall?

NOTE: If you are builder or specifier please go here for specific building codes requirements.

You’re building a new home or maybe you’re adding an addition or a garage, remodeling a kitchen or a family room. What precautions do you need to take for fire safety?

What if you live in an adjoined condo or an apartment building? Do you need to be concerned if your untrained neighbor imagines himself a Top Chef?

Just what exactly do we need to know when it comes to fire safety in our homes? In this article we review frequently asked questions related to fire safety in residential construction. Understanding what you need to know is an important part of any project.

Understanding Fire-Rating Basics

Q: How are walls fire rated? What is fire resistance-rated construction?

A: A certification process determines the fire-rating of a wall system. It is the wall system, not specific products, that are tested and certified. For example, a fire-rated drywall board is approved for use as part of a certified wall system. A basic wall system could include a drywall board, insulation, light gauge steel stud followed by another drywall board.

Q: What is drywall Type X and where is it used? What is Type C?

A: Both drywall Type X and Type C are approved for use in a 60-minute rated design. The wall systems they are approved for are different, however. Type C fire-rated drywall has more glass fiber reinforcement and other ingredients in the gypsum core that makes its fire-resistive properties superior to Type X.

Q: What is the difference between one-hour fire-rated drywall and three-hour fire-rated drywall and where would each one be used?

A: A 60 minute fire rating is a measure of the amount of time the wall system can withstand fire resistance in a fire-rating performance test. More than one hour is achieved by adding additional layers of boards to extend protection or by adding other elements to the system to make it more robust.

Fire Safety at Home

Q: Where are fire-rated products used in the home?

A: Fire-rated products are not typically used in single-family residential construction except for garages. These products are primarily used in commercial construction (high rises, office buildings, industrial, institutional) and any space requiring an area separation wall such as a hotel or multi-family home.

Q: Why are these products generally not needed in a single family dwelling? What is their role in fire safety?

A: The purpose of fire-rated products is to delay the spread of a fire and extend the time a person has to leave the building. In a single family home, getting out is easier. There are fewer floors and multiple exits so the code focuses more on prevention. You will see requirements around electrical wiring, for example, to prevent fire risks caused by faulty wiring.

Q: If I am replacing or repairing drywall in the garage, do I need to use fire-rated materials?

A: First, fire-rated systems are only required if the garage shares a wall or a ceiling with the home. If you are doing repairs in the garage you should replace with like materials, but remember it is the wall system that is fire rated not the product itself. So if it’s more than a patch job or you’re repairing in an area that overlaps with the main living space, it’s probably best to contact a professional.

High-Rise Living

Q: Do fire codes differ between single family homes, condominiums and multi-unit apartment buildings?

A: Yes, any space requiring an area separation wall (a wall separating adjacent living units) like apartments, condos and townhouses, uses a fire-rated system. They are also required in any egress area in the apartment building.

Q: What fire-rated materials are used in multi-unit dwellings?

A: Drywall Type X and Type C are the industry standards for this type of construction and are used on all exterior-facing and joining walls. Interior walls are traditionally non-fire-rated ½” drywall.

Q: In light of some recent high-profile apartment fires, is there anything renters or owners in a multi-unit building should be aware of when it comes to fire safety?

A: Fire safety is part of the building code. It spells out the necessary requirements for this type of construction. In addition to construction requirements the building code also specifies things such as automatic sprinkler systems, emergency and exit lighting, emergency power supplies and fire alarm systems. In general renters/owners will likely have little say in what construction materials are used per unit but you can request information on system maintenance and notify the facilities department if a fire alarm has been disabled.

Your One Very Important Take Away

Q: So to conclude, do homeowners need to be concerned about the fire rating in their home?

A: No, in residential construction fire-rated assemblies are only specified for garages and most homeowners with attached garages are probably not aware of the fire-rating for that wall. Same can probably be said for occupants of multi-family homes with separation walls, and (unless you are replacing the drywall in an attached garage) there really is no need to be aware. The required fire-rating is specified in the building code. Your builder, your architect, your contractor, they need to be aware.

Q: Are there other ways to improve fire safety at home?

A: Definitely. First, if you are doing home repairs have all work checked by a building inspector. It may seem like a tedious step at times but it’s important to making sure your family is safe. Second, this one is simple but critical. Make sure you have all your necessary smoke detectors and the batteries in them are working properly.

While, you may not need to worry about the fire-rating of your drywall you may want to consider…

Do I need mold-resistant drywall?

Do I need to be concerned about the air quality in my home?

Does my home need more insulation?

More information on this topic:

What is Fire-Rated Gypsum?

What is the Difference Between Regular and Type X Gypsum Board?

Tracked by contently: 


Drywall combustibility group

Flammability group is a conditional characteristic of a certain material that reflects its ability to burn. With regard to drywall, it is determined by conducting a special test for combustibility, the conditions of which are regulated by GOST 3024-94. This test is also carried out in relation to other finishing materials, and according to the results of how the material behaves on the test bench, it is assigned one of three flammability groups: G1, G2, G3 or G4.

Content of the article:

  • Is drywall combustible or non-combustible?

  • Drywall combustibility group

  • Video

  • Fire hazard class

Drywall combustible or non-combustible?

All building materials are divided into two main groups: non-combustible (NG) and combustible (G). To get to the non-combustible, the material must meet a number of requirements that are imposed on it during the testing process. A drywall sheet is placed in an oven heated to a temperature of about 750 ° C and kept there for 30 minutes. During this time, the sample is monitored and a number of parameters are recorded. Non-combustible material must:

  • increase the oven temperature by no more than 50 °C
  • produce a sustained flame for no more than 10 s
  • will decrease in mass by no more than 50%

Gypsum boards do not meet these requirements and are therefore assigned to group D (combustible).

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Drywall flammability group

Combustible building materials also have their own classification and are divided into four flammability groups: G1, G2, G3 and G4. The table below illustrates the standards that a material must meet in order to obtain one of the four groups.




The specified parameters refer to samples that have passed tests on the test of my Method II, according to GOST 3024-94. This method involves placing the sample in a combustion chamber, in which it is exposed to a flame on one side for 10 minutes so that the temperature in the furnace is in the range from 100 to 350 ° C, depending on the distance from the lower edge of the sample.

This measures the following characteristics:

  • Flue gas temperature
  • Time for flue gases to reach their highest temperature
  • Weight of the test piece before and after the test
  • Dimensions of damaged surface
  • Does the flame go to that part of the samples that is not heated
  • Duration of burning or smoldering, both when heated and after exposure has ended
  • Time for the flame to spread over the entire surface
  • Is the material burning through
  • Is material melting occurring
  • Visual modification of the appearance of sample

After collecting and analyzing all the above indicators obtained in laboratory conditions, the material is assigned to one or another combustibility group. Based on the figures that were recorded when testing a GKL sheet with dimensions of 1000x190x12.5 mm according to Method ll described above, it was found that the drywall combustibility group is G1. According to this group, the temperature of its flue gases does not exceed 135 ° C, the degree of damage along the length of the sample is not more than 65%, damage by weight is not more than 20%, and the self-burning time is zero.

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See the following video for a demonstration of drywall flammability testing:

Fire Class yu 670 kg / m³ and a thickness of 12.5 mm according to GOST 30403-96 belong to the fire hazard class K0 (45). This means that when the unloaded material was exposed to fire for 45 minutes, no vertical or horizontal damage was recorded in it, and there was also no combustion and smoke formation.

At the same time, in practice, the bearing capacity of a single-layer plasterboard partition is lost after 20 minutes of fire exposure to the material surface. In addition, it should be borne in mind that the fire safety of a particular drywall partition will depend on its design. Is it installed on a metal frame or on a wooden crate, is there a layer of insulation inside and is it combustible.

[attention type=yellow]In addition to fire hazard and flammability, drywall also has properties such as combustion toxicity group, smoke generation group, and flammability group.[/attention]

According to the toxicity of combustion products, GKL sheets are classified as low-hazard (T1). The smoke-generating ability of the material characterizes it as having a low smoke-generating ability (D1) with a smoke generation coefficient of not more than 50 m² / kg (smoke optical density). For comparison, smoldering wood has a value of this coefficient equal to 345 m² / kg. The flammability group of drywall B2 is moderately flammable materials.

Fireproof refractory drywall: types, requirements, application

Following the beautiful, alluring concept of “European-style renovation” and other miracle finishing materials, technologies supposedly unknown in the Soviet Union; in the everyday life of people seeking to re-plan, renovate their apartment or private residential building, the magic word “drywall” has entered.

Architects with designers, sales consultants of trade organizations selling sheet building materials, foremen of enterprises, organizations involved in interior decoration of office and residential premises, foremen of self-employed workers unanimously told the amazed owners of real estate objects with surprising confidence that drywall is moisture resistant, fire resistant, and besides, it is a very light material compared to brick and reinforced concrete structures. Therefore, they can do anything up to device fire partitions , separation with its use fire compartments , sections in buildings, structures.

Today, when the advertising frenzy has somewhat subsided, it is worth taking a closer look at all the advantages and disadvantages of this, no doubt, good building, finishing material in terms of ensuring fire safety measures and compliance with regulatory requirements when using it.

Fire resistant drywall

Types and types

Since there are not so many varieties of this material, and in order to know how they look, it is easier to tell about all of them. This will help the marking of drywall, the same for all manufacturers, according to GOST 6266-97, which establishes the technical conditions for the production of sheet drywall:

  • GKL – ordinary drywall, often called dry plaster. The color of the sheet is gray, the markings applied to the back of each sheet with indelible paint, stencil, stamp or otherwise – blue. It is intended for carrying out assembly and finishing works on facing walls, ceilings, the device of internal partitions in rooms with normal conditions / microclimate.
  • GKVL – moisture resistant drywall. The color of the sheet material is green, the markings are blue. It is used for work in rooms with damp conditions, possible presence during operation; mold, fungus on lined building structures.
  • GKLO – with flame resistance, most often called fire-resistant, as well as fire-resistant drywall. The color of the sheets is pink or gray, the markings are red. It is used for wall cladding of premises with an increased risk of fire, for finishing evacuation routes and exits , as structural elements passive fire protection building structures.
  • GKLVO – drywall with increased fire resistance and moisture resistance. The color of this marketable sheeting is green like moisture resistant, but the marking is red like fire retardant. It is used for finishing, fire protection of individual building structures, installation of internal fire-resistant partitions in rooms with high air humidity under normal operating conditions.

That is, fire-resistant (refractory) types of drywall according to this GOST include GKLO and GKLVO.

It would seem that we can put an end to this, but rule-making in Russia, incl. concerning PB issues, presents another surprise. It turns out that there is another GOST 32614-2012 that establishes those. conditions for gypsum building boards, put into effect on January 1, 2015, and at the origins of both documents in force today is the well-known company Knauf – a “trendsetter” in the production of all types of drywall in Europe and the CIS countries.

Actually, everything would be fine, but this document adopted a completely different marking of types of sheet gypsum board, which is not surprising, because. the details section indicates that this document has been prepared based on a translation of a European standard. First of all, all types of these sheet products are now called not drywall – GKL, but gypsum building board – GSP with the letter designation of the type of material in “foreign” letters:

  • A – the usual type. According to GOST 32614-2012 GSP-A corresponds to GKL.
  • D – with a given density.
  • F – with increased resistance of the gypsum core to fire, due to the introduction of mineral fibers and / or other additives into it. GSP-DF corresponds to fire-resistant gypsum plasterboard GKLO.
  • H – moisture resistant. GSP-N2 corresponds to GKLV.
  • I – with increased surface hardness.
  • P – with applied gypsum plaster or glued tiles.
  • R – increased strength.

Fire and moisture resistant drywall GKLVO corresponds to GSP-DFh3, i.e. there are still only two kinds and types of fire-resistant cardboard.

Characteristics and requirements for materials

The technological characteristics of GKL / GSP are the same – this is the basis of sifted, finely ground gypsum raw materials, cleaned of impurities, formed into a single mass with the addition of water, various binders, including those special for certain types of commercial material, between two layers of dense, resistant paperboard:

  • Reduces hygroscopicity – for moisture-resistant varieties.
  • Solid mineral additives – for types with increased strength, surface hardness.
  • Chamotte clay, non-combustible mineral fibers – in fire-resistant types of drywall / gypsum building board.

An important characteristic when ordering / supplying, for transportation, construction and installation works – standard sizes of finished commercial products:

  • For GKLO, GKLVO. Width – 0.6 and 1.2 m; length – from 2 to 4 m in increments of 50 mm, thickness – from 6.5 to 24 mm.
  • For GSP-DF, 0.6 to 1.25 m wide; length – from 1.2 to 2.5 m, thickness – from 9.5 to 15 mm.

Fire-resistant characteristics of fire-resistant cardboard, as well as all other types of gypsum boards, according to GOST:

  • GSP / GKL belong to the combustibility group G1 – combustible, with zero self-burning ability: according to the ability to smoke – D1, according to flammability: GSP – V2, GKL – V 3.
  • GKLO, GKLVO resistance to fire impact must be at least 20 min.
  • The assignment of GKL, GSP to a less flammable group is possible only on the basis of appropriate tests of samples of serial products of a particular manufacturer.

Conclusions: the name that has developed in the everyday life of designers, builders, finishers in relation to this material is more of an advertising character, because the fire resistance limits of fire-resistant cardboard based on test methods, the minimum requirements of GOST 6266-97 is 20 minutes, GOST 32614 and even less – 15 minutes, so it is rather fireproof drywall.

Groups of fire-retardant efficiency of drywall

But, this material, in addition to the fact that it practically does not burn, has a lot of other advantages that make it, in terms of its combination of qualities, with proper design, performance of constructive fire protection of wood , metal structures, very attractive for use both in new-build and reconstructed facilities; during major repairs, redevelopment of premises in buildings for various purposes, but more on that later.

Test of refractory drywall

Test procedure

It is carried out when serial commercial products are put into production, and then periodically – at least 1 time per quarter; as well as when changes are made to the technological process of production, new materials are introduced, additives are introduced into the formulations of the feedstock. According to GOST, the test procedure for resistance to fire is similar, but according to GOST 32614 it is carried out under more stringent conditions:

  • Three sheets of GKL or 6 sheets of GSP are taken from a batch of marketable products.
  • Two gas burners are sent to the cut sample, to achieve a value of 800 ± 30 ℃ – for GKL before destruction, measuring the resistance to an open flame in minutes, normally not less than 20 minutes; 1000±50℃ – for HSP for 15 minutes (norm) or until destruction.
  • All samples are tested, and if at least one of them does not pass them, having lost integrity, having collapsed into two or more parts; then the tests are considered unsatisfactory, a batch of GKLO, GKLVO or GSP-DF cannot be accepted as a fireproof / fireproof material.

Application on objects

Fireproof cardboard is usually used in the following way:

  • In finishing, facing walls, ceilings on evacuation routes in public, administrative, industrial and domestic buildings.
  • In the decoration of walls, ceilings, installation, sheathing of internal partitions in private residential houses, cottages built of wood materials, both to create even surfaces for plastering, painting, wallpapering, and in order to increase the fire resistance of buildings, safe installation of lighting wiring.
  • When lining a fireplace, walls around solid fuel stoves.
  • When installing air ducts for general exchange, exhaust ventilation, installation of suspended ceilings.
  • When facing wooden, metal beams, rafters of structures of attic floors of residential buildings, incl. in multi-storey buildings.
  • When installing internal partitions during the redevelopment of premises. So, a fire-resistant plasterboard partition is not a myth if a metal frame is used in its creation; all voids inside are filled with non-combustible mineral substances, such as fire-retardant basalt material; the surfaces on both sides and the junction with the fire walls are treated with fire-retardant plaster.

Use of fireproof drywall

The importance of using fireproof paperboard for wood interior finishes in private residential areas, escape routes in place of combustible finishes in public buildings cannot be overstated; after all, this significantly reduces the risk of fire from low-power ignition sources, from short circuits, overheating of electrical wiring at the junction of wires / cables, installation electrical products; ensures the safe evacuation of people.

It is generally recognized that Knauf fire-resistant drywall, produced and widely used, is in demand in Russia, has excellent fire-resistant characteristics and product quality. So, according to some estimates, more than 70% of fireproof sheet material marked GKLO, GKLVO, GSP-DF is sold under the trademark of Knauf.

In addition, in the past few years, the company has launched on the market an innovative sheet material “Knauf-Fireboard” with a thickness of 12.5–24 mm, which can rightly be called a truly fire-resistant drywall, based on the results of fire tests, confirmed by obtaining certificates of conformity:

  • it belongs to the NG group – non-combustible materials.
  • It consists of a gypsum core with the addition of fiberglass and vermiculite, and all surfaces, except for the ends, are covered with fiberglass.
  • Designs of fire-prevention partitions on a metal frame created on its basis by Knauf; single-layer and multi-layer linings of internal load-bearing metal structures of building structures; even without filling with non-combustible mineral plate, roll materials, certified by the laboratories of VNIIPO Ministry of Emergency Situations for 45, 60, 90 min fire resistance.