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Appendix 8 : Analysis of Rooftop Tile Cutting Exemption for Rule 310

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Analysis of Rooftop Tile Cutting Exemption

Entities which conduct rooftop tile cutting operations construct tile roofs for residential homes and commercial 

projects. As part of the construction of tile roofs, employees must sometimes cut concrete tiles with hand-held gaspowered saws on rooftops at residential and commercial sites, all of which have pitched roofs. The cut tiles are then 

fit into various parts of the roof such as the valleys, hips, cupolas, and roof ends. The number of tiles that must be

cut on any roof varies from around ten (10%) to twenty (20%) percent. Because each tile is slightly different, it 

must be measured and cut as it is laid down. For that reason, the tiles are cut one at a time. During the tile cutting 

activity some dust may be generated.

Evaluate Source Category Impact

The 2005 periodic PM10 emissions inventory for Maricopa County provides emission estimates from point, area, 

nonroad mobile, onroad mobile and biogenic sources. EPA guidance documents, including “Introduction to Area 

Source Inventory Development” as well as permit and emissions data in the MCAQD’s Environmental Management 

System (EMS) database, and previous SIP inventories, were evaluated to develop the list of area-source categories 

for inclusion. Some source categories were deemed “insignificant” because there are no large production facilities 

and/or very few small sources, and therefore emissions were not quantified. 

Rooftop tile cutting is not an explicit source category in the 2005 periodic PM10 emissions inventory because there is 

no EPA guidance, emission factors or any other information available on estimating emissions specific to rooftop 

tile cutting. The following construction-related dust sources are assumed to be included in construction emission 

estimates: demolition and debris removal; site preparation (earth moving); and general construction (i.e. vehicular 

traffic, crushing, screening, material transfers, and other operations). Because rooftop tile cutting is an activity that 

occurs during residential and commercial construction, emissions from rooftop tile cutting are presumed to be 

included in construction emissions estimates. 

Maricopa Association of Governments used a grid-based dispersion modeling to evaluate source contributions 

impacting the Salt River monitors (Durango Complex and West 43rd Avenue)1

. The contribution from construction 

activities ranged from 1.00 to 19.57 μg/m3

, depending on the monitor and whether it was a low or high wind design 

day. A formal request for exemption from Maricopa County Rule 310 from Ballard Spahr Andrews & Ingersoll, 

LLP, indicates that the total number of tiles that must be cut on any roof varies from around ten (10%) to twenty 

(20%) percent.2

. 

The MCAQD has not data on how much of construction emissions may be apportioned to tile cutting; however, 

applying a conservative assumption that twenty (20%) percent of the contribution from construction activities are 

from tile cutting, results in a contribution between 0.20 to 3.91μg/m3 (1.00 to 19.57 μg/m3 * 20%). This estimated 

contribution falls well below the 5 μg/m3 value EPA generally presumes to be de minimis for a 24-hour average.3

1 Maricopa Association of Governments, "MAG 2007 Five Percent Plan for PM-10 for the Maricopa County 

Nonattainment Area", December 2007, Appendices Volume Three, pp. V-59-102. 2 David J. Armstrong, "Formal Request for Exemption From Maricopa County Rule310, Fugitive Dust From Dust 

Generating Operations for Rooftop Tile Cutting", addressed the Ms. Joy Rich, letter, June 5, 2008. 3

U.S. Environmental Protection Agency, State Implementation Plans for Serious PM-10 Nonattainment Areas, and 

Attainment Date Waivers for PM-10 Nonattainment Areas Generally; Addendum to the General Preamble for the 

Implementation of Title I of the Clean Air Act Amemdments of 1990, 40 CFR Part 52, August 16, 1997.

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Identify All Control Options

Safety Issues When Attempting to Control Dust on Rooftops Studied by 

NIOSH 

The difficulties inherent in requiring dust-control measures for rooftop tile cutting and alternative solutions have 

been studied by the National Institute of Occupational Safety and Health (NIOSH) in 20064

Engineering Control Options Studied by NIOSH

. In many cases, 

proposed approaches to implement dust-control measure for rooftop tile cutting activities (either to limit worker 

exposure via inhalation or to attempt to control PM emissions released to the atmosphere) have been proven to be 

ineffective, cost-prohibitive, or contradictory with worker safety.

The 2006 NIOSH study evaluated the effectiveness of the following engineering controls in reducing respirable 

dust, silica exposures, and noise during tasks where roofers cut concrete roofing tiles. This two-day study evaluated 

the following four roofing tile saws and one tile cutter:

 Hytile tile cutter. The Hytile cutter used a chisel-on-wheel system where a steel wheel scribes lines on the roof 

tile before the chisel breaks it. The cut is not as smooth as a powered hand saw, but should be acceptable where 

the edge is overlapped with another tile.

 Bosch 1364 hand-held electric-powered saw with add-on LEV. The Bosch 1364 hand-held electric-powered 

saw was equipped with local exhaust hood connected by a 2" flexible hose to a vacuum cleaner equipped with a 

HEPA filter.

 Partner gasoline-powered saw. The Partner gasoline-powered saw did not have any local exhaust ventilation

(LEV) on it. It was equipped with water spray nozzles that were not in use at the time of the evaluation.

 Revelation saw with add-on LEV. The Revelation saw consisted of a Skill electric-powered saw with an 

aftermarket local exhaust ventilation installed. The local exhaust ventilation consisted of a shroud attached to 

the cutting plan of the saw; the shroud was then connected to a small electric axial fan, which is intended to 

collect dust at the point of generation. After passing through the fan, the dust was collected and retained on a 

cloth bag which also served as a filter media.

 Electric-powered Partner Bronco water backpack saw. An electric-powered Partner saw was used in 

conjunction with the Bronco water backpack. The saw was equipped with water spray nozzles intended to 

control the dust generated when cutting concrete tiles. The use of water raised concerns among industry 

representatives about staining of roofing tiles. 

Other Control Options Considered by MCAQD 

 Applying water or dust suppressants

 Cutting Tiles on the Ground

 Shrouding

Eliminate Technically Infeasible Control Options

 NIOSH found that the Partner saw with Bronco water backpack was highly unfavorable because it was too 

heavy and water creates a slipping hazard on the roof. Material discoloration was also found to be an issue of 

the water suppression technique, since water stains the concrete tiles. The Bosch 1364 hand-held electric 

powered saw was considered to be too heavy and was also considered to be cumbersome to use due to the 

addition of a 2" vacuum hose line from the roof to the vacuum cleaner. The Revelation saw was considered 

unacceptable by all the observers because the dust collector, to be effective, required the saw to be pulled by the 

worker towards himself, necessitating the removal of the blade guard. The Hytile tile cutter produced less 

respirable dust than conventional saws with no control or with add-on LEV controls but could only be used for 

cutting about 40% of the roofing tiles while roofing a house. The major concern about the Hytile cutter is that 

the quality of the cuts may not be as smooth as required for certain roofing applications. The gasoline powered 

4 John W. Sheehy, Alberto Garcia, and Alan Echt, "In-Depth Survey Report of a Demonstration and Evaluation of 

Roofing Tile Saws and Cutters Controlling Respirable and Crystalline Silica Dust", U.S. Department of Health and 

Human Services, National Institute for Occupational Safety and Health, Cincinnati, Ohio, September 2006.

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Partner saw was considered acceptable and required no electric hook-up; however, the silica exposures using 

the Partner saw would probably result in respirable dust concentrations above the occupational exposure limits.

 Applying water or dust suppressants - The MCAQD accepts that applying water or dust suppressants during 

rooftop tile cutting operations is infeasible based on NIOSH's findings that water creates a slipping hazard on 

the roof and material discoloration was found to be an issue of the water suppression technique, since water 

stains the concrete tiles.

 Cutting Tiles on the Ground - The rooftop tile cutting entities posed several constraints with this option. One 

is that carrying cut tiles up a ladder would violate OSHA ladder rules that require at least one hand on the ladder 

at all times and that an employee not carry any object or load "that could cause the employee to lose balance 

and fall. Second, is a pulley system to raise cut tiles from the ground is not feasible because there is no place to 

attach a pulley system to the unfinished roof. Also, potential damage to the tiles is an issue due to the increased 

handling of the tile. Third, using a fork lift or cherry picker to move cut tiles from the ground to the roof, is not 

feasible because such equipment is not available at every house under construction and having this equipment 

available for every house would be cost prohibitive. 

 Shrouding - The rooftop tile cutting entities identified several constraints with this option. First, a shroud over 

the roof would have to be at least eight feet over the height of the roof, and, even if it could be made structurally 

sound, would be cost prohibitive and would expose workers to extreme heat (summertime temperatures in 

Maricopa County are regularly over 110 degrees, without a shroud), low visibility, and potential exhaust 

buildup from the gas-powered saws. Another type of shrouding, commonly referred to as the semiencapsulation of a work area, uses light-weight materials such as polyethylene and aluminum. Typically, it is a 

6' x 6' x 6' frame box that is covered on the top and three sides with polyethylene sheets. The same 

characteristics that make the frame box light and portable render it impractical and dangerous to workers on a 

roof. A gust of wind can easily blow the frame box off the roof, taking the worker(s) down with it. A shroud 

and its framing increases the number of tripping hazards on a roof, including limiting visibility of such hazards 

as roof edges and holds in a roof.

California Exempts Rooftop Tile Cutting from Dust Exposure Rules 

The California Department of Industrial Relations, Division of Occupational Safety and Health (Cal/OSHA) 

recently acknowledged difficulty in balancing issues related to dust control and worker safety in its recent revision 

of its construction safety regulations. A construction safety regulation enacted in October 2008 (Subchap. x, Art. x; 

http://www.dir.ca.gov/Title8/1530_1.html) requiring measures to reduce employee exposure from dust-generating 

operations includes an explicit exemption for rooftop tile cutting activities. In its Final Statement of Reasons 

(http://www.dir.ca.gov/oshsb/concreteandmasonryFSOR.doc) describing the proposed changes to the regulation, 

Cal/OSHA concluded that:

...the prospect of using dust reduction systems appears at this time, considering the currently available 

technology and lack of information about its compatibility with roofing operations, to raise legitimate 

concerns about its feasibility, effectiveness, and susceptibility to creating slipping, tripping, and falling 

hazards when used in conjunction with roofing work on structures where fall distances can be fatal or 

seriously injurious. (cite 37)

Conclusion

There is no EPA guidance, emission factors or any other information available on estimating emissions specific to 

rooftop tile cutting. Because rooftop tile cutting is an activity that occurs during residential and commercial 

construction, emissions from rooftop tile cutting are presumed to be included in construction emissions estimates.

The MCAQD has no data on how much of construction emissions may be apportioned to tile cutting; however, 

applying a conservative assumption that twenty (20%) percent of the contribution from construction activities are 

from tile cutting, results in a contribution between 0.20 to 3.91μg/m3

. This estimated contribution falls well below 

the 5 μg/m3 value EPA generally presumes to be de minimis for a 24-hour average. 

Mindful of the numerous previous unsuccessful attempts to develop procedures that effectively control PM 

emissions from rooftop tile cutting while not endangering worker safety, and in light of the fact that emissions from 

this limited activity are assumed to have a negligible contribute to total PM emissions throughout the County, an 

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explicit exemption of rooftop tile cutting activities for Rule 310’s opacity standards has been deemed the most 

suitable approach to balance air quality, worker safety and overall cost concerns.

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