CEMP-ET
TI 809-53
01 May 1999
CHAPTER 1
GENERAL
1-1. PURPOSE AND SCOPE. This document provides guidance for the selection of appropriate
roofing systems for a specific structure under consideration.
1-2. APPLICABILITY. These instructions are applicable to all USACE elements and their contractors
responsible for roofing system design, installation, and maintenance.
1-3. REFERENCES. Appendix A contains a list of references used in these instructions.
1-4. CONTENTS. Because at no time in the history of roofing has such a wide choice of materials and
roofing system options been available, the objective of these instructions is to provide a road map for
the selection of appropriate roofing systems. To utilize a road map, the user must know the point of
origin and the destination. In the case of roofing, there are two distinctively different starting points: 1)
In new design, the roof system selection can be part of the building design. For example, the building
can be strengthened to support a heavy roof system, or the slope increased to accommodate the
minimum required for the desired roof system. When dealing with an existing structure, weight, existing
slope, and compatibility with existing materials all become constraints. 2) With an occupied building,
construction noises, fumes, fire hazards, and building access during re-roofing all take on increased
importance. Arrival at the destination (e.g., a satisfactory roof system) can take more than one route.
Each path has considerations unique to that particular roof system. The principal variables involved are
discussed in this document and supplemental resources are provided. Satisfactory roofing performance
comes from the careful selection, specification, installation, and maintenance of roofing systems.
Design alerts are provided in each chapter where special attention may be needed. Chapter 2 gives a
general guide to selecting a path while Chapters 3 through 10 provide more detail on that particular
route.
a. Problems. Roofing systems are exposed to the full brunt of the weather and can leak or fail
prematurely if not properly designed, installed, or maintained. Leakage can adversely affect the
function and mission of the building the roof is designed to protect. Since modern roofing systems
contain considerable thermal insulation, moisture intrusion lowers thermal efficiency and hinders energy
conservation efforts. Wet materials can support fungus or mildew and emit odors leading to sick
buildings. At the end of the roofs' life, these construction materials are bulky and are a burden to
landfills. Efforts should be pursued to use recyclable materials.
b. Design Considerations. The main design considerations of both water-shedding and low-slope
roofing systems are discussed. Water-shedding (steep) roofing systems include shingles and shakes
derived from asphalt or wood, metal, slate, tile, and architectural metal panels. Low-slope roofing
systems include bituminous built-up (BUR) and modified bituminous (MB) roofing, single-ply (i.e., PVC,
EPDM), sprayed-in-place polyurethane foam (SPF), and structural standing seam metal roofing systems
(SSSMR). General guidelines for selection and design considerations of roofing are found in Chapter 2.
Once a tentative roof selection is made, the user is referred to more detailed information in Chapters 3
through 10. For those existing, occupied buildings, refer to re-roofing and re-covering in Chapter 11.
Chapter 12 covers roof maintenance as a design factor.
c. Appendices. Appendix B (Bibliography) includes subjects for further study and useful WEB sites.
Appendix C contains acronyms used in these instructions. A Glossary of roofing terms is contained in
appendix D. SI/I-P conversion factors for metrication are included in Appendix E.
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