Construction Hazards: Breaching HI-Impact XP Wallboard with Fiberglass Mesh

by Brian Ward

Although HI-Impact® wallboard is not a new fire service concern, many departments and firefighters are unfamiliar with it. In many building construction classes with which I am involved for my department and neighboring departments, only about 30 percent of the firefighters are familiar this issue. After reading this article, ensure that everyone in your department is familiar with the product, since you never know when you encounter it. The videos in this article show how difficult it is to breach, the difference between HI-Impact and standard drywall, and mesh burning characteristics.


After a couple of our company officers and their firefighters encountered this product, they began to wonder about a couple of items. First, how difficult is it to breach and what are the best tools to use? Second, how many occupancies feature this product that we are not aware of? These questions led to research and eventually to testing the material for ourselves. Several other agencies have also tested these materials, and Captain Peter Skeris of the Charlotte (NC) Fire Department wrote about firefighter breaching tests (Fire Engineering, “The Next Generation of HI-Impact® Wallboard,” October 2006).


HI-Impact wallboard is considered an abrasion resistant, high-abuse material that is discussed in-depth below in occupancies. It is heavy with a smooth surface, comes in 1/2- or 5/8-inch thicknesses, and is impact and fire resistant. HI-Impact is identified by the purple paper on its surface, which is only visible during the construction phase, and the fiberglass mesh embedded within the gypsum core. It is also important to note that this wallboard comes in various types, each with varying degrees of impact resistance. These types and their impact-resistant are as follows:

  • HI-Impact 1000 (.010-inch Lexan®) 264 ft-lbs

  • HI-Impact 2000 (.020-inch Lexan) 846 ft-lbs

  • HI-Impact 3000 (.030-inch Lexan) 1,450 ft-lbs

  • HI-Impact 8000 (.080-inch Lexan) more than 2,188 ft-lbs (the 8000 series was discontinued in 2004)


Because of the economy and the high cost of this wallboard, its use is apparently on the decline. The HI-Impact series was developed for commercial use, but the 1/2-inch HI-Impact can be found at some local stores. Some occupancies that use it but want to save money use the material only on the bottom four feet of a wall, replacing it with standard drywall on the upper four feet. Nevertheless, we have identified structures in our own district that use HI-Impact wallboard in such occupancies as classrooms, corridors, daycare centers, assisted-living centers, retirement homes, detention centers, prisons, and dormitories. Designed to withstand impact, this material may be found in many high-traffic areas where walls will take abuse.

The Tools

We tested several common engine and truck company tools on HI-Impact wallboard: The sledgehammer, ax, pike pole, closet hook, and the halligan.

(1) Photos by author. Click to enlarge

The Test

Throughout our tests we used the standard HI Impact® XP® wallboard. The stud spacing is on 24-inch centers, common to interior walls found in structures. The wallboard was nailed to the studs using standard wallboard/drywall nails. We also placed the wallboard in the common orientation mentioned above, with HI Impact on the bottom four feet and the standard drywall on the top four feet.

Test 1

The pike pole was the first tool chosen. It penetrated the wallboard, but it had little or no effect on the mesh. The photo shows that although the gypsum was broken into two pieces, the mesh was still very much intact. After reviewing the pictures below, watch the first video and pay particular attention to the amount of time and effort that it takes to successfully breach the wall. Remember that even after the wall is breached, the entire backing or mesh must be cut; otherwise going through it is very similar to getting caught in small-gauge wire. Notice the difference in impact resistance between standard drywall and HI Impact.


Test 2

In the second test, we used the same setup as the first, but used a fresh firefighter wielding a halligan. Notice how the forked end was the best choice in the test video; it not only penetrated and broke the gypsum, but also cut the mesh strands at the same time. After reviewing the potential time and energy that using the pike pole required from the first firefighter, the halligan looks to be the best option. The halligan took approximately four swings to penetrate the drywall and 30 swings to create a hole large enough for a firefighter to pass through.

Test 3

As we did in the first two tests, we put in a fresh firefighter and changed tools, this time using a standard ax. Notice the difficulty of breaching through the wall even though the ax has a perfect blade for cutting through the gypsum and mesh. As the firefighter starts to chop the wallboard, obviously the best method with the ax, he stops to attempt to use blunt force to the face of the wallboard, which does nothing but exhaust him. After a couple of attempts, he returns to chopping through the wallboard and eventually breaks through it. After he completes chopping the wallboard, watch as he tries to pull some of the strands away. The ax seems to be a fairly effective tool and, although there was not the same amount of difficulty as with the halligan, it seems that a very methodical technique of cutting every single inch is needed to effectively cut through the mesh. The ax took approximately 38 chops with the blade end to create a hole large enough for a firefighter, but penetrated the wallboard after six swings.

Test 4

For the fourth and last breaching test, we found the biggest and strongest man we could to swing a sledgehammer and see what would happen. It was very labor-intensive and produced nothing to recommend the sledgehammer as an effective tool in this situation. For comparison, we compared different types of sledgehammers and their effectiveness. After 14 swings, the eight-pound maul did not breach the wallboard at all. The 12-pound sledgehammer did not breach either, but broke the stud after 14 swings.

Test 5

The final test was performed to determine if the mesh would burn. The last video shows that it does not take much to ignite the mesh; it burns as easily as paper. In the beginning, we used a propane torch to ignite the mesh, but at the end of the last video, a firefighter used a simple lighter to ignite the mesh.


After reviewing the performance of all the tested tools, the halligan was obviously the best option for breaching the wall. Most firefighters carry some sort of tool in their gear, either a combination of tools, cutters, or a simple knife. Make sure that you have something in case of entanglement. If a firefighter encounters the mesh and has difficulty getting through it, remain calm, make sure the gypsum is removed, then pull out your knife and cut the strands away.

When breaching walls in a structure such as a school, detention center, and or other facility, remember that if you encounter resistance not common to standard drywall, move up four feet and try again. This offers two benefits: First, it will tell you what type of drywall/wallboard that you are up against. Second, it allows you to relay this information so that if the rapid intervention team (RIT) is activated, it can select the appropriate tool(s) for the type of construction.

As for knowing in advance what we are getting into and the hazards that we may encounter, we have to preplan again and again. We never know what we may come up against. We discovered that this construction material was in our territory because of a couple of company officers and firefighters kept their eyes open.

I would like to thank all the company officers and firefighters (Lieutenant Michael Thomas, Lieutenant Mike Boehkle, Dwanye Anderson, Firefighter Scott Coleman, and Firefighter Maurcio Galvis) who did the research and performed these tests. For more free training information on similar topics, visit the Training page at

Brian Ward is a training officer for Gwinnett County (GA) Fire Department and the vice chairman of the Metro Atlanta Training Officers. Brian is an advocate for the State of Georgia Everyone Goes Home program. He holds an associate’s degree in fire science and is pursuing his bachelor’s degree. He is also the founder of and can be reached at

Subjects: Breaching walls, truck company operations, firefighter training videos

No posts to display