Loss Prevention Services
Protecting Our Global Community of Customers

Roof Design & Protection
HIGHLY PROTECTED RISK (HPR) ASSET PROTECTION “STARTS ON THE ROOF”

Overview
The roof is a buildings most critical and yet most vulnerable
asset. They serve the purpose of completing the building
envelope along with the walls and floor and carry the bulk of
the load of a buildings weatherproofing purpose. Once
constructed, the roof is often one of the least maintained
portions of a building. The symptoms of a failing roof are rarely
evident until the process is well underway or the stresses ofsevere weather allow it to fail. This guideline is intended todraw attention to best practices for roof design, re-roofing androutine maintenance of roofs.

PurposeRoof failure has catastrophic consequences

Without a roof, all of the assets within a facility become exposed to hazards without vital protection. From a risk
assessment standpoint, a buildings roof is a single point failure mode potential. Utilizing the approach outlined in thistechnical resource will equip the user to build a firm foundation for critical asset protection and business continuity.
When considering new construction, major renovations, roof replacement or updating your risk management plan,follow the TMA HPR Loss Control “WIND” advice as a best practice.

• Wherever your facility is located, all new important structures should
be designed to meet applicable standards• Investigate all existing important structures for conformance toappropriate standards• Necessary retrofit upgrades should be strategically consideredfollowing the advice of your Account Team• Decide in advance to meet these guidelines by inclusion in corporate
design specifications
Hurricanes are among the many causes of severewinds

Roof Design & Protection
Design & Construction
Tokio Marine America (TMA) HPR Property Loss Control windstorm
guidelines adhere to the technical advice detailed in the referenced
FM datasheets and follow the FM ‘RoofNav #’ approval
methodology for new construction and re-roofing. Achieving full
approval requires careful planning and coordination both prior toand during construction to ensure all aspects of the standards aremet. An approved roof consists of components, fastening andinstallation methods that merge to form a system summarized usinga ‘RoofNav #’. This identification number is utilized to verify that thedesired combustibility, windstorm resistance and other natural
hazard protection goals desired such as external fire resistance andhail are met.

A new roof is a major investment, ensure it is welldesigned.

The required windstorm design is based upon building height, base wind speed determined by geographical location
and a ‘ground roughness’ factor. The required design is summarized by a numerical code (e.g. 1-90). The “1” in thiscode identifies the construction as meeting Class 1 combustibility standards while the ‘90’ indicates the relative
windstorm rating. The lowest windstorm rating is 60 and the higher thenumber, the more windstorm resistance the system provides. Whileindirectly related to uplift pressure, this number should not be directly
confused with the required uplift pressure. The RoofNav # chosen should
be listed to meet or exceed the required windstorm design. All roofs
meeting these guidelines require fastening enhancements at perimeter andcorner areas that are more vulnerable to uplift.

TMA HPR Loss Control Plan Review services areavailable to assist with your project

Retrofitting for better protection
An existing deficient roof or roof cover cannot easily be upgraded to meet applicable guidelines without a completereplacement. This fact may result in decisions to improve protection being deferred for decades until major
construction or re-roofing occurs. However, there are retrofit options that will permit targeted risk improvement toenhance windstorm resistance. While such retrofits cannot always meet all aspects of the guidelines such as hailresistance or combustibility, retrofits may still be valuable to protect existing facilities from windstorm events that often
strike with little to no warning.

Tokio Marine Management, Inc. does not represent, warrant, or guarantee the appropriateness, validity or accuracy of this information in every
situation. This information does not necessarily cover every
possible condition, protection, hazard, situation or exposure and is not warranted to comply with laws, regulations, codes or standards in every jurisdiction. This information is representative of reasonable
practices in the industry. However, you may wish to investigate whether these recommendations are applicable to your specific operations. Loss control is the responsibility of your management.
© 2020 Tokio Marine America, All Rights Reserved.

2|P a g eRoof Design & Protection•Flashing Securement – A perimeter flashing system meeting applicable guidelines with a continuous‘cleat’ or ‘hook strip’ offers the best protection along the edges of a roof where many wind uplift events
originate. It is notable that a roof cover meeting these guidelines may fail due to unsecured or defective
flashing. Conversely, a roof that does not fully meet these guidelines will perform better when flashing issecured.
o Secure loose, single piece or disconnected sections of continuous cleat flashing using minimum No.
8 screws with neoprene washers spaced minimum 1 ft. on center.
o Space the fasteners 6 in. on center within 12 ft. of the corners for added protection.
o Replace retrofitted flashing with an approved flashing system at the next re-roofing.

•Increase Perimeter & Corner Fastening – All roofs and roof covers that meet referenced guidelines
are provided with additional fastening in the corner and perimeter areas of the roof. This is because theperimeter of a roof is subject to approximately 1.7 times the ‘field’ or center of the roof uplift pressure while
corners are subject to 2.6 times the field uplift pressure. Many pre-engineered metal building roofs and various
types of roof covers that do not meet applicable guidelines typically lack sufficient perimeter or corner fastening
enhancements. Standing seam metal roofs cannot be easily retrofitted due to the need for additional purlins
to act as fastening points; however, other roofs may be able to be easily retrofitted with additional fastening.
oooooooThrough fastened or lap seam, metal roofs are easily
retrofitted by driving additional fasteners through themetal deck into the existing purlins. Standard fastening
for this type of roof is 1 ft. on center. As a general rule,
perimeter areas should receive one additional fastenerin between each existing fastener. Corner areas should
receive two additional fasteners equally spaced.
Roof covers such as built up, modified bitumen and all
single ply types may be similarly retrofitted in perimeterand corner areas.
The retrofit fastening plan depends upon the building height, wind speed exposure, ground roughness,the presence of 3 ft. or higher masonry parapet walls and the fastening the current system utilizes.
Retrofit fastening in most cases may be completed by driving fasteners with an appropriate fastenerplate directly through the existing roof cover into the roof deck.
Single ply and modified bitumen retrofits may be sealed using strips of new roofing material applied
directly over the retrofitted fasteners.
A qualified roofer should be utilized to complete fastening retrofits to ensure appropriate repairs to theroof cover areas affected are completed.
Corner and Perimeter areas are defined in the reference document “Wind Design” and include peakareas of pitched gable structures and some areas where adjacent buildings intersect.

Tokio Marine Management, Inc. does not represent, warrant, or guarantee the appropriateness, validity or accuracy of this information in every
situation. This information does not necessarily cover every
possible condition, protection, hazard, situation or exposure and is not warranted to comply with laws, regulations, codes or standards in every jurisdiction. This information is representative of reasonable
practices in the industry. However, you may wish to investigate whether these recommendations are applicable to your specific operations. Loss control is the responsibility of your management.
© 2020 Tokio Marine America, All Rights Reserved.

3|P a g eRoof Design & Protection
Summary of the risk
The risk of damage to your facility during a windstorm is significant and may result from many factors. The damage
resulting from a windstorm has the potential to severely interrupt business for extended periods of time due tosignificant damage to equipment, stock and utilities. To best protect the assets located within your facility, begin
outside on the roof with a windstorm risk engineering assessment. Then, take the necessary steps during newconstruction, re-roofing and on a retrofit basis to ensure your investments are well protected when nature strikes.

Reference Documents
FM Data Sheet 1-28 “Wind Design”
FM Data Sheet 1-29 “Roof Deck Securement and Above Deck Roof Components”
FM Data Sheet 1-31 “Panel Roof Systems”
FM Data Sheet 1-9 “Roof Anchorage for Older, Wood-Roofed Buildings”
FM Data Sheet 1-30 “Repair of Wind-Damaged Single- and Multi-Ply Roof Systems”
FM Data Sheet 1-32 “Inspection and Maintenance of Roof Assemblies”
FM Data Sheet 1-34 “Hail Damage”
FM Data Sheet 1-35 “Vegetative Roof Systems”
FM Data Sheet 1-49 “Perimeter Flashing”
FM Data Sheet 1-52 “Field Verification of Roof Wind Uplift Resistance”

A service of the Tokio Marine America Loss Control Department.
TMM is committed to the highest customer trust.
We exist to deliver ANSHIN (safety, security and peace of mind) to our customers by providing the highest quality services.
This information is provided solely as a client service. Tokio Marine Management, Inc. does not represent, warrant, or guarantee the appropriateness, validity or accuracy of this information in every situation.
This information does not necessarily cover every possible condition, protection, hazard, situation or exposure and is not warranted to comply with laws, regulations, codes or standards in every jurisdiction.
This information is representative of reasonable practices in the industry. However, you may wish to investigate whether these recommendations are applicable to your specific operations. Loss control is theresponsibility of your management. | © 2020 Tokio Marine America, All Rights Reserved.
Tokio Marine America (TMA) is the marketing name for Tokio Marine America Insurance Company (TMAIC), Trans Pacific Insurance Company (TPI), and TNUS Insurance Company (TNUS).

Revised 7/27/2020