FREQUENTLY ASKED QUESTIONS

Fire (25)

What is the difference between Class A and Firecode® branded materials?

Class A signifies that a panel attained a flame spread index of 25 or less (based on 100 for untreated red oak) when tested in accordance with the Standard ASTM E 84. The Firecode® brand signifies that the panel has been classified as a protective membrane in a floor-ceiling or roof-ceiling assembly in accordance with the Standard ASTM E 119. All Firecode® protective membranes offered by USG have attained a Class A rating.

Does the ceiling tile and grid system alone provide a fire-rated assembly?

No. The ceiling system achieves a time rating based on the entire assembly which includes roof deck or floor deck assembly.

Industry Terms and Definitions (15)

Why is LR important?

When the proper type of lighting fixture is used with a high LR ceiling, there can be savings in both initial construction costs as well as long-term energy costs. The concept is to use the ceiling to reflect light back into the occupied space.

What does LR stand for?

LR stands for light reflectance. It is a measure of the percentage of light which is reflected off of a given panel surface. Typically, the whiter and smoother the ceiling panel, the higher the LR value.

Installation and Application (184)

How do I mix plaster?

You will need a bucket, scale and mixing equipment. Mixing could be accomplished through basic hand mixing with a large spoon, but mechanical mixing is preferred. An electric drill with a cage mixer head attached is good for small batches.

The first step involves measuring and adding enough water to the bucket to achieve the desired consistency. You then need to weigh out enough gypsum plaster to meet the proper ratio for the selected water volume. Sift the plaster into the bucket of water and allow the plaster to soak for 1 to 2 minutes. Follow this immediately with mixing, generally for 1 to 2 minutes based on product.

NOTE: If mixing by hand, use vigorous stirring action. After mixing and pouring the gypsum slurry, make sure to clean all tools and the mixing vessel before the plaster hardens.

For more detail on mixing, see USG publication IG503, Plaster Mixing Procedures.

Does the ceiling tile and grid system alone provide a fire-rated assembly?

No. The ceiling system achieves a time rating based on the entire assembly which includes roof deck or floor deck assembly.

Product Specific (99)

What does LR stand for?

LR stands for light reflectance. It is a measure of the percentage of light which is reflected off of a given panel surface. Typically, the whiter and smoother the ceiling panel, the higher the LR value.

What is the difference between Class A and Firecode® branded materials?

Class A signifies that a panel attained a flame spread index of 25 or less (based on 100 for untreated red oak) when tested in accordance with the Standard ASTM E 84. The Firecode® brand signifies that the panel has been classified as a protective membrane in a floor-ceiling or roof-ceiling assembly in accordance with the Standard ASTM E 119. All Firecode® protective membranes offered by USG have attained a Class A rating.

Residential (14)

Can gypsum panels be installed horizontally?

Gypsum panels can be installed horizontally or vertically. Installing the board horizontally lessens the total amounts of joints to be taped by 25%.

What is the best compound to use for repairing cracks?

Sheetrock® Brand Durabond® Setting-Type Joint Compounds and Sheetrock® Brand Easy Sand™ Lightweight Setting-Type Joint Compounds are the best products to use for repairing cracks.

If you want to use a ready-mixed joint compound, Sheetrock® Brand All Purpose Joint Compound works well.

Specialty Uses (13)

What is the minimum NRC recommended for open office plan environments?

It is best to use a minimum of .70 NRC and up to .80 - .90 NRC panel for this type of application.

Which USG Ceiling panel will work the best in a commercial kitchen application?

Sheetrock® Brand Gypsum Lay-In panel is approved by both the USDA and the FSIS for use in commercial kitchens.

Sustainability (3)

Isn’t fly ash bad for concrete and isn’t it a potential hazardous product?

Fly ash often is used as a filler in concrete. When used at excessive levels, fly ash and concrete has been cited as one of the reasons for excessive moisture in concrete slabs.

In Durock™ EcoCap™ Self-Leveling Underlayment, the fly ash is not used as filler but rather as a source of aluminum and silicon in the geopolymer reaction that takes place. In this case, the fly ash contributes significantly to the strength, self drying and setting characteristics of the product due to the geopolymer reaction.

What is the recycled content of Durock™ EcoCap™ Self-Leveling Underlayment?

75% of the cementitious binder is recycled material.

Technical (77)

What is the difference between Class A and Firecode® branded materials?

Class A signifies that a panel attained a flame spread index of 25 or less (based on 100 for untreated red oak) when tested in accordance with the Standard ASTM E 84. The Firecode® brand signifies that the panel has been classified as a protective membrane in a floor-ceiling or roof-ceiling assembly in accordance with the Standard ASTM E 119. All Firecode® protective membranes offered by USG have attained a Class A rating.

What is the difference between wet-felted and cast ceiling panels?

Wet-felted panels are typically mechanically perforated and fissured. They are very dense and more economical than other types of ceiling panels. Cast ceiling panels are non-perforated and are manufactured in a different “cast” process, hence its name, that enhances their surface appearance and provides excellent sound absorption and durability.

Product Storage (13)

How far in advance can I order ceiling panel before installation?

Storage time of materials at the job site should be as short as possible, and environmental conditions should be as near as possible to those specified for occupancy. Excess humidity during storage can cause expansion of material and possible warp, sag, or poor fit after installation. Chemical changes in the mat and/or coatings can be aggravated by excess humidity and cause discoloration during storage, even in unopened cartons. Cartons should be removed from pallets and stringers to prevent distortion of material. Long-term (6-12 months) storage under uncontrolled environmental conditions should be avoided.

Can I lean Fiberock® Brand Panels against walls?

Fiberock Panels are heavy and should be stacked flat on the floor. Serious injury can occur from falling panels.

Warranty (6)

What kind of warranty does Fiberock® Brand Aqua-Tough™ Underlayment have?

Fiberock® Brand Aqua-Tough™ Underlayment has a 20-year limited warranty. See complete warranty for details.

Do Sheetrock® Brand Glass-Mat Liner Panels offer an exposure warranty?

They offer a 12-month exposure warranty, and they can be used in any fire-rated cavity shaft wall and separation wall system assembly.