Make It Safer 

With 

Roof Screen

Instructional Materials
A Brief History of Roof Screen

Roof screening for ground control originated with 

metal miners in the western United States. At first 

chain-link fence was used, but because it was so 

difficult to handle, the miners started installing a 

more rigid welded wire screen used in the concrete industry. Eventually coal mines in the west 

began to use screen, and now more and more 

coal operations, especially longwall mines, are 

installing roof screen on a regular basis. Screen 

use has recently increased in the Illinois basin and 

is now making its way to underground coal mines 

in the eastern U.S. 

i

Table of Contents

A Brief History of Roof Screen................................i

Introduction..........................................................1

Specification / Custom Ordering ...........................5

Size of Roof Screen

Grid Size

Reinforcing Wire

Edge Cuts

Strength

Installation............................................................7

Manual Materials Handling Tips ...........................9

Materials Handling System (MHS).......................11

Personal Bolter Screen (PBS)...............................13

Conclusion / Best Practices..................................14

Other Sources of Information / References .........16

ii
Introduction

Coal miners, especially roof bolter operators, work in a hazardous environment where they are frequently exposed to poor roof conditions, 

putting them at risk of a rock fall injury. Over 450 reported injuries each 

year result from rock falls; 99 percent of those reported are not caused 

by a major roof collapse, but from falls of 

smaller rocks from the 

mine roof (Robertson 

et al., 2004). Roof bolts 

are not failing; rather, 

the rocks are falling 

from the uncontrolled 

area in between the 

bolts. e loose rocks 

that cause injuries 

are usually just a few 

inches thick but weigh 

on average 280 lbs. 

(Molinda et al., 2003).

e highest percentage (44%) of rock 

fall injuries happen to roof bolter operators, followed by continuous miner 

operators. Roof bolters must work in 

the most hazardous place in the mine: 

the freshly cut face. eir bolting activities, especially the drilling process, can 

disturb the mine roof and cause pieces 

of rock to fall. A particular concern 

is the unprotected space between the 

Automated Temporary Roof Support 

(ATRS) and the bolter canopy. Even after the roof is bolted, continuous miner 

(CM) operators and other miners can 

be injured by falls of loose rock. 

Loose rocks can fall from between roof bolts and injure miners.

Roof screen provides overhead protection 

to the bolter operator during the entire 

bolting installation process.

1

Compare the coverage provided by roof mats (a widely used surface support sometimes called straps or “bacon strips”) versus roof screen. 

A mine with 18-ft. entries that installs 16-ft. x 10-in. steel straps every 4 ft. 

of advance achieves 18% roof coverage. By installing 16-ft. x 5-ft. sheets of 

screen instead, the coverage can increase five-fold to 89%. 

The material cost for the screen is only about 25% higher. 

18 ft.

Roof Coverage

18%

ROOF MATS

Pillar

ROOF SCREEN

Roof Coverage

89%

18 ft.

Pillar

“Our top isn’t heavy necessarily, it doesn’t load up, but we have 

small pieces of roof rock that fall out between roof bolts. We 

tightened up our roof bolt pattern, but yet that didn’t help. But the 

screening has solved that problem.” 

~ Mine Safety Director, West Virginia

The Roof Screen Advantage

2
Surface controls, including steel straps, header boards, large surface 

plates, and steel screen or mesh help protect miners from loose rock. 

e effectiveness of a surface control depends on the amount of roof 

that it covers. Roof screen is by far the most effective surface control 

because it covers the most roof area. 

Roof screen has been 

proven to dramatically 

reduce the number of 

rock fall injuries at 

coal mines. One mine 

in northern Maryland 

began roof screening 

routinely and on-cycle 

in 1997 because of very 

poor roof conditions 

and a high occurrence of 

small rock falls. Before 

the mine started installing roof screen it 

averaged fourteen rock fall injuries per year; after 1997, rock fall injuries reduced dramatically. At another mine in the Illinois basin, similar 

geologic circumstances were encountered which also required roof 

screening. Rock fall injuries subsequently dropped from an average of 

eight per year to only two injuries over the next nine years (Robertson 

et al., 2004). ese injury reductions were attributed to the overhead 

protection that screen provides to operators throughout the entire bolt 

installation process, 

including the area 

between the ATRS and 

the canopy. In addition 

to roof bolter operators, all others (CM operators, etc.) who work 

below the installed 

screen will have overhead protection from 

rock falls.

 “Before the roof screening, it was hard to travel in on 

the track and back out without having to clear rock off 

the track. It was just a matter of time before someone 

was going to get some rock on them. Now you can go in 

and out of the mine everyday and travel the track entry 

freely and not have to worry about getting a piece of 

rock on you or someone else getting a piece of rock on 

them.” 

 ~ Mine Safety Director, West Virginia 

Roof screen can cover a large area of the mine roof.

3

Data collected from two years before and several years after the start of full-scale roof screening shows the dramatic 

reduction in rock fall injuries.

4
Specification / Custom Ordering

Roof screen can be ordered from the manufacturer or vendor with the 

following options:

Size of Roof Screen – Manufacturers can produce roof screen in various sizes and shapes (width and length) depending upon the needs of 

the mine operator.

• A full sheet of screen (commonly 16-ft. x 4-ft.) is generally wide 

enough to stretch across both ATRS rocker pads of the bolting machine. 

• A smaller sheet of screen (e.g. 

5-ft. x 5-ft.) called a Personal 

Bolter Screen (PBS) can be 

easily handled by one person.

Grid Size – e grid size of 

roof screen is the size of the 

opening between the wires in 

both directions. A typical grid 

size is 4-in. x 4-in., but other 

sizes are currently being used. 

Reinforcing Wire – Roof 

screen can be ordered with extra wires to reinforce the screen 

in selected areas. Some mines 

choose to add reinforcing wires 

around the perimeter of the 

screen, while others place them 

in the locations where bolts will 

be installed. Reinforcing wires 

are sometimes called “indicator 

wires” because they help show 

bolting machine operators 

where to install roof bolts. (a) Reinforcing wire can be fabricated into the screen at various 

locations. (b) Grid size is the space between the wires.

grid size

b

a

5

Edge Cuts – It is important 

to order roof screen with 

minimal, if any wires protruding from the edges of the 

screen. Protruding wire ends 

can catch materials causing 

tears and snags and are a potential cut/puncture hazard. 

Certain screen manufacturers 

are able to cut the edge wires 

down to an eighth of an inch, 

while others are able to “trim 

cut” the wires so that they do 

not protrude at all from the 

edge of the screen. 

Strength – e strength of the screen depends on the gage (diameter) 

of the steel wires and the grid pattern of the screen. As the gage of the 

steel wire decreases, the diameter increases along with the strength and 

rock load heights that the screen can maintain (as seen in the graph below). A common choice of gage for coal mines is an 8-gage steel screen 

that can hold up to 2 feet of rock.

9,000

8,000

7,000

6,000

5,000

4,000

3,000

4

2

3

1

Steel Screen Strength (lbs.)

Gage of Steel

Rock Load Height (ft.)

3 4 5 6 7 8 9 10

Steel Screen Strength

Rock Load Height

NIOSH studies showed the relationship between gage and strength/rock load heights for roof screen 

bolted on 4-ft. centers with a 4-in. grid size. (Robertson et al., 2003)

Screen that is “trim cut” has no wires protruding from the edge of 

the screen.

6
screen is secure against the roof, roof bolts 

are installed using normal procedures.

a. Outside-controlled - With most outsidecontrolled bolting machines, the screen 

can be stored either on top of the rear of 

the machine or behind it on the ground. 

It may also be pulled behind the machine 

by a rope or chain. To install the screen, 

both bolting machine operators retrieve a 

sheet, carry it to the front of the machine, 

and then place it on top of the ATRS. 

b. Walk-thru - With a walk-thru bolter, the 

screen is also stored on top of the ma-

chine, on the ground, or pulled behind 

the machine. Operators carry the roof 

screen up the center of the machine be-

fore placing the screen across the ATRS. 

c. Walk-thru with a Materials Handling 

System (MHS) - A Materials Handling 

System retrofitted onto a walk-thru 

bolting machine has numerous machine 

innovations, including a mechanized 

screen tray that makes materials han-

dling of screen and bolting supplies much 

easier and safer.

e results of recent roof screening time stud-

ies and observations conducted by NIOSH 

(Robertson et al., 2004) were the following:

 Roof screening added between 5 and 25 

percent to normal bolt installation times. 

 e addition of the third operator reduced 

load and installation times by 40 percent.

Installation

Machine manufacturers have been working 

with mine operators to design innovations 

that will make roof screening safer and easier. 

NIOSH has observed and performed produc-

tion time studies of different roof screening 

procedures at numerous coal mines and found 

that the installation procedures and screenhandling times depend on the following:

 Number of persons – Aside from the two 

bolting machine operators, some mines 

utilize an additional person (often the utility 

person or scoop operator) to help retrieve, 

carry, and handle the roof screen. 

 Operator experience with the installation of 

roof screen – As mine operators and bolt-

ing machine operators find better ways and 

gain experience installing roof screen, the 

installation time generally decreases. 

 Size and Weight of the Roof Screen – e 

size and weight of the roof screen can affect how easily and quickly the roof screen 

is handled and installed. In general, two 

operators are needed to handle a full sheet 

of screen whereas a single operator may 

be able to easily handle a personal bolter 

screen. 

 Type of twin-boom roof bolting machine 

Roof screen is being installed using three 

types of bolting machines. Each can include 

various devices (clamps or wires) that can 

be used to help make sure that the roof 

screen does not slide across the ATRS when 

it is being raised against the roof. Once the 

abc

–

78
injury to the worker when handling and installing roof screening materials follow:

 Closely estimate the number of sheets needed near a face area, then 

try to deliver only that specific amount. Contact the roof screen vendors or manufacturers to customize the number of sheets per bundle. 

e goal is to avoid rehandling the excess sheets.

 Keep lifting tasks between the elbow and knee levels. Lifting from 

below the knees or above the elbow levels increases the risk of injury. 

 Minimize twisting and bending at the waist when picking up roof 

screen. Keep your back straight and turn slowly before proceeding to 

walk with the screen.

 Always use two workers to carry a full sheet of screen. Keep your 

back straight and keep the screen as close to your waist as possible.

 Using various mechanical devices, keep the roof screen from sliding 

off of the ATRS to avoid re-handling.

 Working overhead is difficult but a major task for roof bolter operators. Although it is difficult to eliminate this component, reducing the 

time spent in this posture is essential. 

 Keep the bolting machine organized making sure that operators can 

easily retrieve bolting supplies. A screen tray and material pod system 

(as shown on p. 11) are machine innovations that keep the bolting 

machine orderly and more efficient. 

 Keep the walkway areas on or around the bolting machines clear of 

clutter and debris to reduce tripping hazards.

More scientific research is still needed to minimize the effort required 

to handle and install roof screen. NIOSH researchers are planning a 

study on ways to reduce and eliminate the physical effort involved in the 

roof screen installation process as well as increasing efficiency. Included 

in this study will be the testing of new machine designs and materials 

handling innovations.

10

 Installation times were reduced by 50 percent as operators gained 

more experience handling and installing roof screen.

 Roof screen installations were 30 percent quicker using a walk-thru 

bolter when compared to the outside-controlled machine.

 Operator maneuverability while installing roof screen was easier using a walk-thru compared to the outside-controlled bolting machine.

 e total screen handling times were 40 percent lower using the MHS 

compared to the regular walk-thru bolting machine with the majority 

of the time saved during screen loading onto the bolting machine.

e procedures and handling times for installing roof screen on-cycle 

will vary from mine to mine. Mine operators should work to find the 

best way to install screen, keeping the health and safety of their workforce in mind at all times.

Manual Materials Handling Tips

While the best way to reduce injuries associated with manual materials handling is to automate or mechanize the process, it is not always 

feasible or cost-effective. Manual materials handling can be done effectively and efficiently if careful consideration is given to the methods and 

principles used. Musculoskeletal injuries may result from task design 

that requires physical effort in excess of workers’ capabilities and limitations. In the mining industry, over 40% of the injuries are musculoskeletal (MSDs) and cumulative in nature, with bolting machine operators 

experiencing the highest percentage. e highly repetitive job of roof 

bolting coupled with an increased workload due to screen installation is 

cause to give attention to preventing MSDs.

 

Because roof screen has been determined to save many acute injuries 

such as cuts, contusions, and/or fractures, screening should be considered a necessary practice to ensure the safety of our mining workforce. 

Nevertheless, the installation process should not be so laborious as to 

deter operators from using this method to reduce the risk of rock fall 

injury. With that said, procedures to reduce the risk of cumulative 

9
moved to the center of the machine to protect the screen from damage, 

especially when tramming around corners. 

e MHS also reduces the amount of materials handling required for 

the entire bolting process through the use of material pods that are 

loaded outside the mine. A larger left pod and smaller right pod contain 

supplies such as bolts, plates, cap boards, and resin boxes – enough for 

a full shift. Both the left and right pods are loaded into the scoop bucket 

and then delivered to 

the rear of the bolting 

machine. e pods are 

then pulled directly off 

the scoop in the same 

manner as the roof 

screen, by a remotecontrolled winch system. e risk of sprain/

strain, slip/trip, crush, 

or cut types of injuries is greatly reduced 

with the pod system. 

NIOSH studies have 

also found that two 

miners can supply the bolting machine as much as three times faster 

with the pod system than three workers can when hand-loading bolting 

supplies on a machine without the pod system (Robertson et al. 2003).

Scoop bucket loaded with pods of bolting supplies for the MHS.

“In the old days when we had to load the bolter, everything 

was done by hand. We had to load plates, all the glue, the 

bolts – tops and bottoms, everything. We had quite a few 

accidents – back injuries, shoulder injuries. With the material 

pods, we don’t have to do that. Everything is pre-loaded so it 

has reduced our accidents immensely.” 

~ Section Mechanic, Illinois

12

Materials Handling System (MHS)

e Materials Handling System (MHS), 

currently being used 

by several mines, can 

greatly simplify the 

screening process. Its 

most notable feature is 

a mechanized screen 

tray for storing the roof 

screen on the bolting 

machine. An entire 

bundle of screen can 

be pulled onto this tray 

at one time by a remote-controlled winch 

system (as seen in the 

video) which practically eliminates the handloading of roof screen 

onto the bolting machine. Front and rear 

lift cylinders decline 

the tray towards the mine floor, and the tray can be placed at a ramped 

angle so that the bundle can be pulled onto the tray easier. NIOSH studies have shown that by using the screen tray system, roof screen can be 

loaded on the bolting machine five times faster than when hand-loading 

each piece of screen (Robertson et al., 2003).

During roof screen installation, the screen 

tray is raised to an elevation and angle 

which allows the bolting machine operators to pull a sheet of screen off of the 

screen tray easily. e screen is then placed 

across the ATRS and installed with roof 

bolts. is tray can also be lowered and 

 “And since we went to this 

MHS system, our injuries, as 

far as bending, back injuries, 

and the twisting turning 

type have really dropped 

dramatically.” 

~ Shift Foreman, Illinois

The screen tray of the MHS is tilted back toward the ground for the loading of 

a bundle of screen (a) by a remote-controlled winch (b,c).

b c

a

11
Conclusion / Best Practices

Roof screening has been found to be an effective method for controlling poor roof conditions. Compared to other supports used to control 

loose roof rock, roof screening provides the most mine roof coverage. 

e experience of mines that use roof screen shows that injuries from 

falls of loose rock have been reduced dramatically. Increased use of 

regular, on-cycle roof screening in adverse conditions will help the mining industry reduce the annual number of rock fall injuries.

To help mines develop simpler and safer roof screening systems, the following best practices have been compiled:

1. Perform a biomechanical analysis of installation procedures to determine physical and time requirements (e.g., determine postures and 

handling methods which reduce physical workload).

2. Consult with roof bolting machine manufacturers about innovative ways to make roof 

screening easier and safer. ese could include:

 Rounded edges on bolter canopy tops to 

reduce material snagging and decrease the 

physical effort required to move the screen 

into place.

 Retractable clamps or a wire assembly on 

the ATRS that can hold the screen in place 

while it is being raised against the mine 

roof. 

 e use of a separate tray to make roof 

screening easier to handle and provide for 

better storage of roof screen on the bolting 

machine.

(a) Bolter canopy with rounded 

edge. (b) Clamps hold the screen 

in place while the ATRS is raised 

against the roof, then retracts 

automatically.

a

b

14

Personal Bolter Screen (PBS)

In thin coal seams, handling a full sheet of screen can be awkward. In 

other cases it may not be necessary to install a full screen. For these 

situations, NIOSH has developed a smaller screen that can be installed 

by a single bolting machine operator. Called the Personal Bolter Screen 

(PBS), this screen can vary in size but is typically around 5-ft. wide x 5-

ft. long. e PBS with a reinforced perimeter wire weighs just 11 lbs. 

As seen in the video, the PBS can be installed with pattern bolting and 

has a 6-inch overlap of each screen. Trial installations have shown that 

the PBS is easy to handle and can be stored easily on the bolting machine. Material costs are comparable to roof straps and it affords three 

times the roof coverage. Single sheets of PBS can also be used for occasional supplemental support where roof conditions call for it or where 

specific tasks are being performed.

The Personal Bolter Screen is easily handled by one person.

13
Other sources of information

 Personal Bolter Screen Poster (http://www.cdc.gov/niosh/mining/

topics/groundcontrol/PBSposter2_GroundControl_2003.pdf)

 Cornelius, K.M., Turin, F.C., Reducing Roof Bolter Operator Cumulative Trauma Exposure. Holmes Safety Association Bulletin January 

1997 pp. 1-8. (http://www.msha.gov/PROGRAMS/HSAPUBS/1997/

JAN97.pdf)

 Turin, F.C. et al. (1996). Human Factors Analysis of Roof Bolting Hazards in Underground Coal Mines, US Bureau of Mines, RI 9568.

References

Robertson, Susan B., Molinda, G.M., Dolinar, D.R., Pappas, D.M. [2003]. 

Best Practices and Bolting Machine Innovations for Roof Screening. 

2003 SME Annual Meeting, Cincinnati, OH, Feb. 24-26, 8 pp.

Molinda, Gregory M., Robertson, Susan B., Mark, Christopher, Dolinar, 

Denis R. [2003]. Covering the Roof Reduces Crippling Injuries Underground. Coal Age Vol. 108, No. 10, pp. 20-26.

Robertson, Susan B., Cooper, D.P., Wiehagen, W. J. [2004]. Safety Improvements for Roof Bolter Operators. ASSE Professional Development 

Conference, Las Vegas, NV, June 7-10, 17 pp.

16

 Remote-control operations, winches and material pods may eliminate or reduce material handling difficulties. 

3. Ensure that no body parts extend past the last row of bolts when 

placing a sheet of roof screen across the ATRS by backing up the 

bolting machine a foot or two after each sheet of screen is installed. 

4. Try to order roof screen that does not have wires protruding from 

the edges of the screen (trim cut) to reduce materials handling difficulties and lessen injury potential.

5. Consider roof screen fabricated with reinforcing wires to help sustain the integrity of the screen and aid in proper bolt spacing.

6. Try using small sheets of 

plywood or matting between the roof bolt plate 

and screen to prevent the 

roof bolt plates from cutting 

the screen wires.

7. Fit anti-fatigue mats on 

top of the bolting machine 

walkway to provide a more 

cushioned standing surface, 

reducing fatigue on the feet, 

knees, and lower back.

“Since we’ve gone to the screening we’ve definitely improved safety. It’s 

hard to tell how many accidents that we’ve prevented by installing the roof 

screen. I like it. The men like it. It makes us a much safer coal operation

to work at. Had we started this from day one – I wish we would have – we 

may have prevented several other accidents as well.”

~ Mine Safety Director, West Virginia

Plywood installed between roof bolt plate and roof screen.

15
Delivering on the Nation’s Promise:

Safety and health at work for all people

through research and prevention

 For more information about occupational safety and health 

 topics contact NIOSH at:

 1.800.35.NIOSH (1.800.356.4674)

 Fax: 513.533.8573

 email: pubstaft@cdc.gov

 www.cdc.gov/niosh

For more information on

Roof Screening contact:

NIOSH Pittsburgh Research Lab

Susan Robertson

412.386.6720

SBRobertson@cdc.gov

Chris Mark

412.386.6522

CMark@cdc.gov

Print Design and Layout: David L. Caruso, NIOSH

Video Production: Chuck Urban, NIOSH