STC and SECUROCK® Roof Boards: Do You Hear What I Hear?

Concerns about building occupants’ comfort continues to grow from both an owner and regulator standpoint. One major concern is how to manage sound in our living and work spaces.

In the past, a building’s sound issues were tackled from the interior looking at walls and ceilings. Now, there is a continued focus on the exterior of a building with a desire to create systems that can better handle outdoor environments (air traffic, highway traffic, etc.) and sensitive buildings (hospitals, schools, etc.) in a more effective way. In this post, we will provide an overview of Sound Transmission Class (STC), how it is measured and tested, several ways to increase STC, and finally how SECUROCK® Roof Boards help create better environments for STC.

STC is the most common sound isolation standard used today and is for airborne noise (unwanted sound). Typically measured in dB (decibels), the higher the STC number the better that system is for blocking airborne noise. One thing to remember, dB’s are a logarithmic unit and displayed on a logarithmic scale, therefore, going from 40dB to 50dB isn’t a 125% increase in perceived sound it actually means the perceived sound is twice as loud. The measurement is over a frequency range of 125-4000 Hz (Hertz) and uses transmission loss to calculate what the STC is. So, STC isn’t necessarily what a system (wall, ceiling, roof, etc.) will stop, but more closely related to a ranking of how well a system can prevent sound transmission. Since STC ignores low frequencies, it also has major limitations in real world applications for areas that are indicated above (for example air traffic has a lot of low frequency noise that is missed by STC). Despite its limitations, STC is an easy number to use and allows agencies and companies to gather data on systems in order to help solve some of a building’s concern around sound.

Testing for STC is typically done by third party laboratories that have trained acousticians.  There are several standards for measuring STC, but the most popular ones are ASTM E90-09 (Standard Test Method for Laboratory Measurement of Airborne Sound Transmission Loss of Building Partitions and Elements) and E413-10 (Classification for Rating Sound Insulation). These ASTM standards create a method for testing airborne sound transmission loss in partitions and obtaining a single number rating called STC.  There is a lot that goes into the actual testing of the partitions, but the general idea is as follows:

• A partition is constructed between two rooms in a laboratory setting.
• While noise is played on one side of the wall, the sound levels over the frequency range of 125-4000 Hz are measured on both sides of that partition.
• The transmission loss of the system is calculated from the difference between the sound levels in the two rooms.
• STC is calculated for that partition based on the transmission loss data collected.

Now that we know what STC is and how it is measured, there are some things to think about in real world applications that might be able to help improve airborne sound transmission. There are several ways to increase the STC rating of a roof/ceiling assembly including adding mass, adding air space, adding absorptive material and decoupling. First, adding mass to a roof/ceiling assembly can have a big effect on blocking sound and this is typically done by adding layers of material such as SECUROCK® Gypsum-Fiber Roof Board.  Second, adding air space within the partition increases the STC. The increasing air space between ceiling tile and a roof deck increases the STC more than having ceiling tile directly under the roof deck.  Third, using an absorptive material like specialized ceiling tile or increase insulation will help increase STC. Finally, decoupling is a mechanical solution that separates layers of the roof/ceiling assembly making it difficult for sound to pass. This typically means using sound clips which USG also manufactures and sells. There are many tricks to increase the STC rating of a roof/ceiling assembly, but remember that everything from the top of the roof membrane to the bottom of the ceiling tile must be considered in order to get the best system.

Lastly, we want to share how SECUROCK® Roof Boards are helping out with this complex issue of building exteriors. We recently did testing at Riverbank Acoustical Laboratories in Geneva, IL to understand some of the effects that STC has with roofing. We took typical roof assemblies and then trialed different configurations. Here are some things we discovered:

• Adding roof boards increased the system STC incrementally
• Glass-Mat and Gypsum-Fiber provided similar results for STC
• The type of insulation does have an effect on STC
• Mechanically attachment and fully adhered systems provided similar results for STC testing

Below is a typical roof assembly that we tested and achieved a STC rating of 41. This assembly had an EPDM membrane, 5/8” SECUROCK® Gypsum-Fiber cover board, two layers of 2” insulation, 5/8” SECUROCK® Gypsum-Fiber thermal barrier, and a 22 gauge steel deck.  We evaluated various construction details of a roof assembly to evaluate their effects on STC rating.

We want everyone to understand that although a roof board adds to the STC rating, the main job of a roof board is to help protect everything below it as well as extend the life of that roof. While a roof board will contribute to the STC of a roof/ceiling assembly, a better reason to choose it is to maintain that STC rating throughout the roof’s useful life.

Please contact your SECUROCK® Roofing Solutions Team for more information and advice regarding your next installation.

Demo the Difference: SECUROCK vs. the Competition

We put SECUROCK head-to-head up against the competition in a 4-part “Demo the Difference” video series. In these side-by-side tests, we compared:

1.  Adhesive Absorption
2.  Cutting
3.  Itchiness
4.  ⅜” SECUROCK Gypsum-Fiber vs. Competitive ½” Glass Mat Roof Board

Watch below to see how our roof boards stack up to the competition!

Adhesive Absorption
First up in our series is a side-by-side adhesive test. This video demonstrates how SECUROCK Gypsum-Fiber will save you both time and money over competitive glass mat products. SECUROCK Gypsum-Fiber has a smooth surface with no glass fibers that will make it easier to roll and push the adhesive quickly across the panel, but ultimately uses less adhesive which will significantly decrease the installation cost. Glass mat products soak up adhesive and ultimately use more than is necessary to properly adhere to. Plus, if you use a glass mat product in adhered systems, you are relying on the bond of that mat to the core, which is why we recommend using products that don’t have a facer for adhered systems. Overall, a better quality system, lower installation cost, and easier to use.

Cutting

In this side-by-side cutting test, you’ll see how SECUROCK Gypsum-Fiber is easier to cut and will leave you with less debris over the competition.  Because it has no facer and is a homogeneous product, all you have to do is score it on one side and snap.

Itchiness

Next up in the “Demo the Difference” series, this video will show you how SECUROCK Roof Boards create less itch when handling.  Because SECUROCK Gypsum-Fiber and SECUROCK Cement Roof Board have no fiberglass in them, it is easy to see why people handling these products don’t have to worry about itchiness.  However, even our SECUROCK Glass-Mat has the same effect because of the high quality mat that we use. This high quality mat means there will be less fibers shedding while it is being moved around. Plus, the higher quality mat gives you a better mat-to-core bond, making it less likely to delaminate when cutting or on the roof than other competitive glass mat roof boards.

⅜” SECUROCK Gypsum Fiber vs. ½” Competitive Glass Mat Roof Board

Last but not least in our series, this video compares ⅜” SECUROCK Gypsum-Fiber Roof Board to a competitive ½” glass mat roof board in regards to weight per panel, compressive strength, flute span, perm rating and moisture rating. Employing advanced technology in delivering an exceptionally strong, sustainable roof board, SECUROCK Gypsum-Fiber roof boards exceed the competition and promises excellent performance in a variety of applications.  So, if you are using ½” glass mat products, chances are that you can use a ⅜” SECUROCK Gypsum-Fiber Roof Board instead and get better performance with a cost savings.

As a leader in the building materials industry for over 100 years, USG is proud to deliver a portfolio of high-quality and high-performing products that give roofing professionals a better choice in the roof board category. All of this adds up to a roof board portfolio that goes above and beyond to meet the needs of any application.

See more videos from SECUROCK Roofing including how-to’s and testimonials at http://www.youtube.com/usgcorporation. To learn more about SECUROCK Roof Boards, please visit http://www.usg.com/securock.

Wind Uplift Explained

Whether for life safety, insurance, or code compliance, wind uplift is a major concern for anyone who manufactures, designs or installs roofing products. In this post, we will provide an overview  of the design process, the two major testing agencies, and how Securock Roof Boards can help you protect against wind uplift in your next project.

When wind hits a building, pressure is exerted against the building as the air pushes against the sides and moves up and around the building.  Wind uplift is a force (pounds per square foot) that occurs when the pressure below a roof is greater than above it. This can happen from many different ways but is usually because pressure above the roof system decreases by high air flow (wind) or pressure increases inside a building from air pressure buildup. When wind uplift is greater than the system was designed for, the roof could potentially lift off the building.

There are many design considerations, but most codes (such as IBC 2012) and design professionals are using the 2010 edition of ASCE 7, or ASCE 7-10 to design a roof system (ASCE is the American Society of Civil Engineers). The old version of ASCE was ASCE 7-05, and with the new version of ASCE 7-10, some things remain the same with the new version, such as factors for design including building location, height and ground surface. However, with the new code, there have also been items that have changed such as the use of new wind speed maps based on risk categories and an expanded seismic area. In addition, there are tools such as www.roofwinddesigner.com that can help with the design.

Once a design professional understands the wind loads on the building, it is time to pick a roof system. For a rated system, most entities (such as IBC 2012) will look to Factory Mutual (FM) or Underwriter’s Laboratories (UL)  for guidance. Because there are differences in how the systems are tested, designers should always compare products using the same test agency numbers.

FM is the default testing standard for wind uplift. Roof assemblies that have been tested can be found on FM’s website. You should know that the testing is based on assemblies, not components. The two main FM  testing standards are FM 4450 and FM 4470.

1. FM 4450 tests Class 1 insulated metal decks.
2. FM 4470 tests all other Class 1 roof covers.

With FM Tests, the roof system is pressurized from below the deck to 30 psf, and held for one minute.  The pressure is increased by 15 psf increments every minute until failure.

UL has two standards for testing wind loads: UL 580 and UL 1897.  You may notice there is no safety factor in the UL numbers. The test is in pounds per square foot.  This is not a design number, but a test number.

1. UL 580 is a dynamic pressure test.  In addition to pressure from below, UL 580 draws a vacuum on top of the membrane. Pressure levels are varied throughout the duration of the test.
2. UL 1897 is a static pressure test in which an apparatus that creates a steady negative pressure is placed on the top side of the membrane.  Pressure is held for one minute and raised by 15 psf increments, until failure.

Wind uplift is a force that occurs when the pressure below a roof is greater than above it, and if the wind uplift is greater than the design of a roof system, it can blow the roof off the building. Design professionals will typically use ASCE 7-10 to find the proper wind load of a building.  Once that design parameter is found, the default testing agencies are FM (4450, 4470) and UL (580, 1897). Properly tested products that meet the design criteria, such as Securock High Performance Roof Boards, will help ensure that a safe building is constructed.
Now, we would like to give you some understanding of where Securock Roof Boards can potentially rate for FM testing.

Finally, using the very common FM 1-90 rating with a typical assembly (TPO adhered to a cover board that is mechanically fastened onto a metal deck), it is easy to see how costs can add up depending on the roof board that you select.  Below is a table of different roof boards for this assembly.  We assumed $.20 / fastener (screw and plate), average roof was 100’ x 200’ (625 4’x8’ roof boards), and it took an average of 2 minutes to screw in a fastener with a labor rate of $20/hour.

As you can see, using Securock Gypsum-Fiber on a 20,000 square foot job can save you as much as $4,333 just in fasteners and labor.  So, not only will you get a great product that will be easier to install, enhance the safety of your client’s building, and is made from 95% recycled material, you will also save money on installation.

Introducing USG’s “Building A Better System With Roof Boards” CEU

Learn how to create an overall better system with roof boards and receive 1 AIA HSW CEH credit in USG’s new Roofing CEU on the Hanley Wood University! Architects, designers and other participants will learn the importance of roof boards and how to create a better roofing system with the use of the most highly-rated types of roof board.

Although the installation cost of a roof is generally less than 4% of the overall cost of the structure, an estimated 60-70% of all construction litigation is roofing. To help reduce the amount of failed roofs on commercial buildings, and to cut down on subsequent litigation, this course is focused on learning about and creating an overall better roofing system.

This course will provide an introduction to roof boards and what they do in various applications, along with information on some of the forces that can negatively impact roofs such as fire, wind, impact, mold, moisture and foot traffic. Participants will learn how the impact of these forces can be measured and reduced. Learning objectives for this course also include listing the different types of roof boards and their attributes, as well as discussing the importance of specifying roof boards in a roof system.

Along with a wide range of other courses, this course can be found on Hanley Wood’s University here: Building a Better System with Roof Boards. All courses at HanleyWoodUniversity.com are free and can be accessed at your convenience 24 hours a day, seven days a week, 365 days a year.

We are pleased to provide this important educational service to the industry and welcome your thoughts and comments on the course here.

SECUROCK Roof Boards— A Weapon Against Fire

Fire is a major concern for every building owner and designer of commercial properties.  Whether it is from inside the building or externally, a fire can cause life safety issues as well as major damage.  Fortunately, roof boards can help contribute to fire safety and lessen this issue for all concerned.  Below are some of the testing agencies that concern themselves with fire ratings, how the SECUROCK Roof Board portfolio can assist in fire safety, and a recent account of how SECUROCK Roof Boards made the difference.

Let’s first look at the two primary certification agencies: UL & FM.  UL (Underwriters Laboratories) is a global independent safety science company offering expertise across five key strategic businesses: Product Safety, Environment, Life & Health, University and Verification Services.  UL has both exterior and interior classifications.  FM (Factory Mutual) is primarily concerned with loss prevention issues. In terms of fire, FM tests are used to judge the contribution of roof assembly components to the spread of fire within a building. Both of these testing agencies are very critical to understanding how building products can contribute to fire safety.

For external fires, UL uses test standard UL 790 (equivalent to ASTM E-108) and FM uses FM 4450 or 4470.  UL 790 has three components: a spread of flame test to see how easy it is for fire to spread, intermittent flame to simulate wind conditions and a burning brand test to simulate burning objects falling on the roof.  From these tests, three classes (A, B, C) are determined with Class A being the best.  For FM 4450 (insulated steel deck) and FM 4470, the roof system is subject to a series of tests that subject it to internal fire, external fire, wind uplift, foot traffic, impact resistance, and susceptibility to heat and damage.

With internal fires, look to UL 1256 and UL 263 as well as FM 4450 or FM 4470.  UL 1256 and UL 263 evaluate resistance to fire that start within a building.  UL 1256 is for fire testing of roof deck constructions and uses two parts to evaluate “White House” and “Steiner Tunnel”.  For UL 263, a P series is given to systems that are able to contain fire and/or retain structural integrity during a given exposure time frame.  And because fire is a concern for parapet walls as well, both ⅝” SECUROCK Roof Boards meet the Type X classification per ASTM C1396, which is a 1-hr load rating on a wood stud wall assembly attached vertically with joints staggered 16 inches on each side and tested in accordance to ASTM E 119. With FM 4450 and FM 4470, a Calorimeter test will measure the fuel added to an internal fire from the roof assembly.  In order to achieve a Class 1 rating, you must pass this test.  A roofing system that qualifies for a FM Class 1 will qualify for the lowest insurance rates from FMG affiliated insurance companies.

We hope that helps with the basics of how products and systems are rated. Here’s how USG’s SECUROCK Roof Board products rate.  As always, fire classification is a complex subject, so don’t hesitate to contact any of our sales representatives, UL, or FM for further clarification.

Click here to download the PDF: Fire rating chart

Click here to open chart in Excel: Roofing Blog Chart

 

Finally, we’d like to share a recent incident that happened on a job that was using SECUROCK Gypsum-Fiber.  All of the pictures shown are from a recent job in Chicago that was under construction when a fire was ignited inside the building from a welder’s torch. This was not an external fire, but an internal fire. Wood blocking at the base of the curb caught fire from the welder’s torches. The fire traveled up the curb and across the roof.  The insulation burned down to the SECUROCK Gypsum-Fiber and was extinguished by the material at that time.  Had it not been for SECUROCK Gypsum-Fiber, more (or perhaps all) of the roof and building would’ve been lost.  Fortunately only a small area of roof board, insulation and membrane had to be replaced.  Regardless, sometimes it’s not only post construction fires that everyone needs to worry about, fires can happen during the construction period as well.

Please let us know if you have any thoughts or questions.

3/8” SECUROCK® Gypsum-Fiber Roof Board— A Choice That Goes Above and Beyond

Roof boards come in all different materials, shapes, and sizes – which is great because it allows you to get the right panel for your application. But sometimes that also means there are great options on the market that people are unaware of until it’s too late. In an effort to make these options known, we’d like to share some attributes of our 3/8” SECUROCK® Gypsum-Fiber roof board so that you’re in a better position the next time you’re choosing a roof board.

Using a 3/8” SECUROCK Gypsum-Fiber roof board may be a better option compared to a 1/2″ glass-mat roof board.  If you look at a typical 1/2″  glass-mat roof board, our SECUROCK Gypsum-Fiber roof board (which is made of 95 percent recycled content) has the same 5” flute span, a better perm rating, scores a 10 on moisture and mold testing, has similar fastener requirements for an I-90, and all at double the compressive strength.  Also, a 3/8” board is a better recover board than other 1/4″ products and most 1/2″ products.

Not only do you get a premium offering over other 1/2″ options, but you also receive the attributes of all of our Securock roof boards that go “above and beyond.”  In terms of cutting, with the 3/8” SECUROCK Gypsum-Fiber roof board you are able to score and snap on the ground or on a pallet with ease, there is no backside mat to cut or delaminate, and there will be less mess. Plus, the 3/8” doesn’t have any itchy glass fibers, which makes it easier to carry and keeps everyone happier and healthier.

Finally, and most importantly, if you’re using adhesive, you’ll save significantly in labor, rollers, and material with a better quality roof (no dry spots) as it applies easier and better with up to 30 percent less.

Recently a consultant and contractor in Illinois recognized the value of 3/8” and requested the switch from a competitor’s 1/2″ to our 3/8” SECUROCK Gypsum-Fiber roof board. Since the switch, they have been extremely pleased with how the 3/8” performs along with the unmatched customer service USG brings. Find a few photos from the job included in this blog post.

You’ll reap all of the benefits of SECUROCK Gypsum-Fiber roof board technology, but at a thickness that is right for your roof.

We recommend a 3/8” SECUROCK Gypsum-Fiber roof board in all low-slope commercial roofing systems, especially fully adhered systems such as single-ply, fluid-applied, built-up, spray foam, metal, and modified bitumen.

If you have any questions please contact us, we’d be excited to hear from you.

Gapping Recommendations for SECUROCK High Performance Roof Boards

Throughout our experience with roofing, many of us have seen movement on roof decks as materials interact with the environment during and after installation. The two main environmental factors are changes in temperature and moisture content. It is common practice to install control joints in the building industry. We see this in sidewalks, walls, floors and so on, allowing for the expansion and contraction naturally occurring in materials. Left unrestrained these materials do not crack or buckle. When panels are butted tightly over large areas and are allowed less than necessary accommodations for expansion; buckling, ridging or crushing is the end result. It is typical to recommend allowances for movement as all building materials are subject to dimensional changes in temperature and moisture.

When looking at physical properties of products there is usually data with the following verbiage like “Linear Variation with change in moisture, “Coefficient of Thermal Expansion,” or “Linear Variation with change in Temperature.” This is basically saying that all of these building materials (including SECUROCK High Performance Roof Boards) are affected by changes in temperature and moisture content. If a product doesn’t explicitly say what its data is, it is a good idea to find out so you can understand how moisture and temperature will effect installation.

It is clear that the environment affects building materials. In order to plan for movement, when installing SECUROCK High Performance Roof Boards, both thermal and hygrometric consequence should be taken into consideration. We would like to help out the community with a quick discussion of how to use these values. As always, design of proper expansion relief is the responsibility of the design professional; please also refer to organizations like NRCA for their guidelines with respect to treating gapping.

The following is an illustration of how to use expansion coefficients for hygral and thermal effects.

Securock High Performance Roof Boards have the following expansion coefficients for hygral and thermal effects:

	Securock Gypsum-Fiber Roof Board	Securock Glass Mat Roof Board
Thermal	8E-06 in/in ºF	8.5 E-06 in/in ºF
Hygral	8E-06 in/in %RH	6.3E-06 in/in %RH

 

 

 

The following tables show gapping allowance for runs with 4’x4’ and 4’x8’ panels for given additive temperature and humidity changes expected; values have been extracted and placed in the table for example. The numbers have been calculated to stay within NRCA guidelines where ¼” is the maximum allowable gap before insulation should be filled (see NRCA for further reference). In this table, ΔT can be defined as initial installation temperature and maximum expected rooftop temperature during install or directly following. The overall rise would be used. Similarly, the overall expected rise in % RH would also be used.

Gap needed per board using 4’x8’ Securock Gypsum-Fiber Roof Boards:

	ΔRH = 0%	ΔRH = 10%	ΔRH = 20%
ΔT = 25°F	.02”	.03”	.04”
ΔT = 50°F	.05”	.06”	.08”
ΔT = 75°F	.08”	.13”	.13”

 

Gap needed per board using 4’x4’ Securock Gypsum-Fiber Roof Boards:

	ΔRH = 0%	ΔRH = 10%	ΔRH = 20%
ΔT = 25°F	.01”	.02”	.02”
ΔT = 50°F	.03”	.03”	.04”
ΔT = 75°F	.04”	.07”	.07”

 

For example:

Given the table above, panels are kept in the shade at ground level and are noted to be 75ºF, then see temperatures at lunchtime on a hot day during installation with a black roof of 150 ºF, your ΔT = 75ºF. If no humidity increase is expected, your ΔRH = 0%. Looking at the table you would gap every 4’x8’ panel by .08” or every 4’x4’ panel by .04”.

So our recommendation is to butt board edges and ends loosely in typical installations and for long, uninterrupted runs, there should be some slight gapping due to changes in temperature and moisture. More tips to help ridging on roofs include installing dry materials into a dry roof, storing boards on the rooftop to avoid thermal swing, and always consulting a design professional and use industry guidelines before installation.

Should I worry about wood fibers in SECUROCK Gypsum-Fiber roof board?

The simple answer is “no.” Some of our customers believe that because we use cellulose fibers from recycled paper in our manufacturing process, we are using wood fibers, which are prone to disintegrating in the presence of moisture.

Cellulose is the most common organic compound on earth. About 33% of all plant matter is cellulose; it is the structural component of the primary cell wall of green plants. The fact is that our Securock Gypsum-Fiber roof board does contain cellulose fiber, but even though cellulose is found in wood, the fibers can be separated out during the paper making process. Our board uses recycled cardboard, also known as Kraft paper. Kraft, the German word for “strong,” actually refers to the type of paper process used. During the “pulping” process, the recycled cardboard is broken down separating most of the fiber components yielding mainly pure cellulose fibers. Cellulose is a natural polymer with a high tensile strength and is not water-soluble. Although SCS (Scientific Certification Systems), who certify Securock Gypsum-Fiber roof board as 95% recycled, states that the board is 10 % cellulose, it actually contains around 2%. Because of fluctuations in manufacturing, the standard practice is to set a maximum of 10%.

USG’s advanced manufacturing technology combines the cellulose fiber with synthetic gypsum. The gypsum and cellulose fiber are co-calcined (heated to a high temperature to remove water) in a reactor. Then another portion of the cellulose fiber is added to the slurry after it leaves the reactor to form a second slurry, which is deposited to form a mat. When the mat sets, it is dried in a board kiln to complete the drying process, leaving the gypsum board rigid, strong, and virtually moisture-free. The panel strength comes mainly from the crystal formation of the gypsum, but adding the recycled fibers helps to form an optimum gypsum crystal structure. In addition, our formula includes a water resistant additive for extra moisture control.

To test our roofing systems, we have gotten panels completely wet and then completely dried them out and a minimum of 95% of the strength was retained. Due to our advanced manufacturing technology, Securock Gypsum-Fiber roof board production delivers an exceptionally strong, high-performance board. The dense concentration of gypsum and cellulose fibers provides exceptional panel and bond strength, low surface absorption, and superior wind-uplift performance with no face layer to delaminate.

As always, it is our recommendation to keep Securock Gypsum-Fiber roof boards dry before, during, and after installation as it is never ideal to have water in a sealed building envelop.

Gypsum through the Ages

Gypsum, a common mineral, has been extensively used in building construction since approximately 9000 BC. When mixed with water and sand it makes a fine-textured paste (plaster) that dries hard and smooth. The oldest traces of plaster renders were found in Anatolia and Syria, and in Israel, gypsum floor coverings from 7000 B.C were found. In 3700 B.C., the Egyptians used gypsum blocks and plaster applied over woven straw lath in the building of the pyramid of Choeps. As a testimony to the strength and durability of gypsum, some of this construction, including walls decorated with murals composed of tinted plaster, is still intact and viewable.

In the Middle Ages, gypsum was used to stucco many buildings and used as cement in in structures such as canals, fortresses, harbors, and shipbuilding facilities.

In 1765, the French chemist Lavoisier analyzed the chemical make-up of gypsum. His research, along with the discovery and mining of gypsum in the Montmartre district of Paris, led to wide use of “Plaster of Paris” as a building material.

In the late 1700s, gypsum became popular as a soil additive. During a trip to France, Benjamin Franklin observed French farmers using it in their fields. He was so impressed that he began to promote it and use it on his farm when he returned to America. Agricultural gypsum supplies were initially imported from Nova Scotia, and American farmers, considering it a miraculous fertilizer, were so anxious to acquire it that a lively smuggling trade began, resulting in the so-called “Plaster War” of 1812. In 1792, when large gypsum beds were discovered in New York, and for roughly the next 100 years, the primary use of gypsum in the U.S. was as a soil additive. Today, 188,000 tons of land plaster are used in the United States each year.

In 1888, gypsum was first used to manufacture wallboard, using Plaster of Paris sandwiched between several layers of wool felt paper. When the plaster set and dried out, the sandwich became a strong, rigid, fireproof building material. Augustine Sackett’s and Fred Kane’s product, called Sackett Board, soon became a replacement for wooden slat lath in many areas. In 1894, Sackett, generally considered the grandfather of the gypsum board manufacturing industry, patented the manufacturing process, over the next eight years opened several production facilities. By 1901, he was producing nearly five million square feet of board annually.

In 1902, 30 independent gypsum rock and plaster manufacturing companies merged to form the United States Gypsum Company. The following year, USG developed its first building product, Pyrobar, a gypsum-based, fireproof tile. In 1909, USG purchased the Sackett Plaster Board Company. Near the end of 1916, a new manufacturing innovation produced boards with a single layer of plaster and paper that could be joined flush along a wall with a relatively smooth surface. Originally called Adamant Panel Board, a sales representative suggested that the company brand the product as “SHEETROCK®”, a non-warping, non-burning wall covering.

Through the 20^th century, USG continued to expand into and lead new markets. In the ‘80s, DUROCK Cement Board offered new water construction solutions. The acquisition of DONN Incorporated and its ceiling suspension systems positioned USG Interiors as the only company to offer complete pre-designed and fully integrated ceiling systems. In the late 1990s, USG developed a new gypsum/cellulose product family called FIBEROCK Brand Panels. In 2005, SECUROCK® Gypsum-Fiber roof board was launched, and in 2010, SECUROCK® Glass-Mat roof board was introduced. Today USG is the largest distributor of wallboard in the United States and the largest manufacturer of gypsum products in North America.

Synthetic Gypsum

USG has been using mined gypsum for more than 100 years and synthetic gypsum for more than 30 years in making building construction products.  The value of synthetic gypsum and the difference between it and fly ash have been the topic of much discussion around the composition of gypsum roof boards. The two are both products of burning coal: synthetic gypsum is made through a process of flue gas desulfurization or “scrubbing” coal plant emissions to remove the sulfur dioxide, while fly ash is a waste product from the burning of coal.  Today, a lot of gypsum products use synthetic gypsum in their manufacturing process including Securock® Gypsum-Fiber roof boards.  We would like to discuss the benefits of synthetic gypsum as well as how it is different from flyash.

Synthetic Gypsum Is Environmentally Friendly

Products that use synthetic gypsum in their manufacturing processes contribute to a cleaner environment in at least two ways by making power plant emissions cleaner and keeping material out of landfills.

First of all, the principal source of synthetic gypsum is from removing polluting gasses from power plants to reduce emissions of harmful materials into the atmosphere.  In the process of flue-gas desulfurization (discussed later), synthetic gypsum is produced which is identical to natural gypsum.

Finally, the synthetic gypsum that is produced would need to be landfilled if another option wasn’t found.  Luckily, because it is the exact chemical match of natural gypsum (CaSO4 ·2H20), it can be used as a direct substitute.  So, manufacturers don’t need to use the resources to mine gypsum and they can use a material that was going to be lost in a landfill – a win on both sides of the sustainability scale.  Synthetic gypsum is one of the ways that Securock Gypsum-Fiber becomes 95% recycled content.

In conclusion, synthetic gypsum provides a powerful environmental solution by taking harmful emissions out of the atmosphere and using a valuable resource rather than wasting away in a landfill.

How Synthetic Gypsum Is Made

Synthetic Gypsum is a by-product of the flue gas desulfurization (FGD) process, commonly known as “scrubbing.”  Flue gas desulfurization is a chemical process to remove sulfur oxides from the flue gas at coal-burning powerplants. Their goal is to chemically combine the sulfur gases released in coal combustion by reacting them with a sorbent, such as limestone (calcium carbonate, CaCO₃).  As the flue gas comes in contact with the slurry of calcium salts, sulfur dioxide (SO₂) reacts with the calcium to form hydrous calcium sulfate (CaSO₄2H₂O) or commonly known as synthetic gypsum.

Flow diagram of the flue-gas-desulfurization process based on lime (CaO) or limestone (CaCO3), which are the sorbents used by 90 percent of FGD systems in the United States.

 

Synthetic Gypsum Driven By Safety

Several groups have developed specifications and guidelines covering the chemical and physical aspects of synthetic gypsum to insure that the material will be safe for manufacturing use.  There are differences in synthetic gypsum and the better the quality of the material the more valuable it is.

USG conducts rigorous testing on both the synthetic gypsum and mined gypsum we use to ensure that the gypsum meets our established quality, purity, and production standards. USG also requires the synthetic gypsum supplier (the power plant) to conduct quality control testing of the shipments of synthetic gypsum to our plants. In addition, USG conducts quality control and assurance testing at our manufacturing facilities and tests both the synthetic gypsum and the mined gypsum we use for purity and the presence of contaminants. These tests are conducted by our own research scientists as well as certified third party laboratories.  And because USG’s number one core value is safety, you can be assured that we only use a safe product for our employees and customers.  The gypsum that USG uses to make its products is safe and meets our quality, purity, and production standards.

Finally, as stated by the U.S. Environmental Protection Agency, FGD gypsum is not a waste product from coal combustion but, rather, is a specially-created product that “serves exactly the same function” as mined gypsum in wallboard.

Synthetic Gypsum Is Not Flyash

There’s a lot going on in the world and it’s easy for us to get confused about things that aren’t in our minds day to day.  One thing that occasional gets misunderstood in the market is how synthetic gypsum relates to flaysh.  Synthetic gypsum and fly ash are completely different substances. Fly ash is not used as a substitute for gypsum because fly ash has a different chemical composition from gypsum. Synthetic gypsum (CaSO₄2H₂O) is produced from FGD and is the chemical equivalent of natural gypsum.  Flyash is a residue generated from combustion and is captured by some type of filtration equipment and is used in various ways but never as a substitute for gypsum.  There are several resources that talk more about flyash.

Conclusion

For more than 100 years, safety and quality have been USG’s core values. We are confident that our products are safe and of the highest quality.  Synthetic gypsum is a material that significantly adds to the positive impact of our environment while being greatly useful as a substitution for natural gypsum.