Low-Slope Metal

Low-Slope Metal

1. General Product Information

1.1 Product Type
1.2 Roofing Components
1.3 Product Manufacturers and Industry Trade Associations
1.4 Manufacturing Process
1.5 Industry-Specific Standard and Code Requirements
1.6 Industry-Specific Flashing and Metals Requirements

Metal panel roofing provides protection from weathering—including heavy snow, wind and rain loads—along with resistance to the effects of hailstorms and wildfires. Due to the composition, metal panel roofing is also resistant to fire, cracks, shrinkage and corrosion. For more detailed information beyond what is provided herein, please refer to resources provided in Section 5 and the manufacturer’s installation specifications.

1.1 Product Type

Low-slope metal panel roofing may be a standing seam roof (SSR), through-fastened roof (TFR), or insulated metal panel (IMP) roof.
An SSR has side joints between the roof panels that are arranged in a vertical position above the roof line. The metal roof panel is secured to the roof substructure by means of concealed hold-down clips attached with screws to the substructure. Through-fasteners may be used at a limited number of locations where simple lap joints occur, such as at ends of the panels and at roof penetrations. The prevalent rib geometries for low-slope metal panel roofs include the trapezoidal or vertical rib profile. If the SSR is attached directly to open framing, it is typically designed to expand and contract and must be allowed to float. The roof clips, or hold-down clips, are concealed in the seam of the panel. It is important that clips be installed in the locations specified on the construction documents. There are two types of clips—fixed clips and sliding clips. A fixed clip is commonly used when shorter panel lengths are involved. Sliding clips allow the SSR to expand and contract.

A TFR includes metal roof panels that are attached directly to the substructure with fasteners that penetrate the roof panels. The fasteners should include an EPDM washer.

IMPs typically have an insulation core clad with either steel or aluminum. IMPs are used in many applications that require high insulating properties and a durable interior liner. These panels can be up to 6 in. thick with excellent R-values to meet the needs of refrigerated warehousing, freezer buildings, and the ever-increasing energy code provisions for thermal insulation. Various manufacturers have different panel profiles and side lap connections. Some use simple side laps with exposed through-fasteners; others use tongue-and-groove systems with hidden fasteners. Some roof systems even have standing seam side laps.

1.1.1 Low-Slope Metal Panel Roof System Description

There are many different types of metal panel roof systems available to meet the performance and aesthetics needs of a building. On the performance level, metal panel roof systems may be structural or non-structural. Structural metal panel roofs—either SSR, TFR or IMP—generally include higher ribs in the panels/profiles, which enable it to carry significant design loads over open framing with spacing intervals of several feet. Non-structural metal roof panels are installed over a structural deck, which is the primary load-carrying component. More frequent attachment is common along the non-structural panel length.

1.1.2 Identification-Traceability

The source and certification of the base metal, as well as the type and thickness of any coatings that have been applied to the metal, is commonly retained by the roofing manufacturer and is typically available upon request. Identification is often linked by the manufacturer’s project or job number, which is generally located on the original plans and frequently written on various elements within the building.

When working with an existing building, recognize that many companies might have changed names, merged with other companies or simply gone out of business. Thus, identifying the manufacturer of a particular profile may be difficult or impossible. However, Section 1.3 below may offer resources to re-create the necessary profile in the event a roof panel needs to be replaced.

1.1.3 Packaging and Storage

Materials should be packaged so as to avoid scratching and chaffing during transit and short-term onsite storage. Storage should be in accordance with the roofing manufacturer’s recommendations.

1.2 Roofing Categories

1.2.1 Roof Pitch Limitations

Metal panel roof requirements are often categorized according to the roof slope. Some codes label roofs as “low slope” when the pitch is 2:12 or less, while “steep slope” applications are on roofs with a pitch greater than 2:12. (For further steep-slope metal panel roof discussion, refer to the Best Practices Steep-Slope Metal information on the IBHS website.) However, other codes and standards set this break point at a pitch of 3:12. Regardless, the International Building Code (IBC), Chapter 15, includes the following requirements for minimum slopes for metal roof panels:

  • An SSR may be installed on a roof down to 1/4 in. on 12 (2% slope).
  • A TFR with lapped, nonsoldered seams without applied lap sealant is permitted to be installed on roof slopes down to 3:12, while seams applied with lap sealant is permitted to be installed on roof slopes down to 1/2 in. on 12.

Additionally, metal panel roofs may be categorized as being either hydrostatic (watertight) or hydrokinetic (water-shedding). For more information on this topic, refer to the MBMA Metal Roofing Systems Design Manual (Chapter 1 Systems Components).

1.2.1.1 Low Slope

Low-slope systems are normally water barrier or hydrostatic in design. However, it is not unusual to combine hydrokinetic (water-shedding) joint details within a hydrostatic (water barrier) low-slope roof system.

1.2.1.2 Steep Slope

Steep-slope applications can be either hydrostatic (water barrier) or hydrokinetic (water-shedding), structural or non-structural. Refer to the Best Practices Guide - Steep Slope Metal resource for more information.

1.2.2 Substrates and Finishes

1.2.2.1 Substrates

Structural metal panel roof systems are supported by open framing that does not require an additional substrate. An example would be for SSR, TFR or IMP installed directly to the top of the roof purlins or bar joists.

In nonstructural low-slope metal panel roofs, structural decking may be attached to the top of the purlins or bar joists. This decking provides support and mounting surfaces for both the rigid board insulation and the metal panel.

1.2.2.2 Finishes

Roof panels made from steel require a metallic coating for corrosion protection. Metallic coatings are typically applied to the steel in coil form prior to fabrication into a specific shape or profile and could either be zinc, which produces galvanized steel, or an aluminum-zinc alloy such as Galvalume®. The most common product used for metal panel roof systems in low-slope applications is unpainted Galvalume®.

A paint finish can add additional corrosion protection to metallic-coated steel roof panels and, depending on the project, can be used to enhance the aesthetic appearance of the roof. When painted, the finish is typically applied to the metallic-coated steel in coil form prior to fabrication into a specific shape or profile.

Roof panels made from aluminum, copper, stainless steel and zinc are generally left unpainted.

1.3 Product Manufacturers and Industry Trade Associations

A partial list of current manufacturers of commercial metal panel roofing and coatings of such products can be found through the following associations’ websites:

1.4 Manufacturing Process

1.4.1 Standing Seam Metal Roofs

SSRs are manufactured from a variety of finishes in a variety of profiles. The material is uncoiled, cut to the appropriate width, roll-formed into the specific profile, cut to length, and packaged for shipment. SSR panels range from approximately 12 in. wide to 24 in. wide. Prevalent SSR rib geometries for low-slope systems are trapezoidal and vertical.

1.4.2 Through-Fastened Metal Roofs

TFRs are manufactured in a similar manner as SSR products. However, TFR products are commonly 36 in. wide and come in a variety of corrugated profiles. Typically, a TFR has ribs 9 in. to 12 in. on-center, with rib heights from 3/4 in. to 1½ in. high.

1.5 Industry-Specific Standard and Code Requirements

Metal panel roofs must comply with the applicable building code, including associated reference standards.

1.5.1 Hail Resistance

Metal panel roof systems can be evaluated for impact resistance to hail damage by either dropping steel balls from prescribed heights, or propelling ice balls with prescribed impact energies.

FM Global and Underwriter’s Laboratory (UL) test standards applicable to metal panel roofs include:

  • FM 4473, Specification Test Standard for Impact Resistance Testing of Rigid Roofing Materials by Impacting with Freezer Ice Balls
  • UL 2218, Standard for Impact Resistance of Prepared Roof Covering Materials

1.5.2 Wind Resistance

Metal panel roof systems must be designed and installed to meet the wind speed specified in the applicable building code. Standing seam roof systems must be tested for wind uplift capacity in accordance with ASTM E1592, Standard Test Method for Structural Performance of Sheet Metal Roof and Siding Systems by Uniform Static Air Pressure Difference or FM 4474, American National Standard for Evaluating the Simulated Wind Uplift Resistance of Roof Assemblies Using Static Positive and/or Negative Differential Pressures. Through-fastened roofs and insulated metal panels are tested under UL 580, Standard for Tests for Uplift Resistance of Roof Assemblies, in order to meet the model building codes. Alternatively, for through-fastened roofs, the model building code allows the wind-uplift capacity to be calculated based on AISI S100, North American Specification for Design of Cold-Formed Steel Structural Members.

For more information on designing metal roofs associated with metal buildings, refer to the MBMA Metal Roofing Systems Design Manual (Chapter 6 Design Practices) and the Guide Specification (Chapter 3 Specifications and Standards) within the document.

1.5.3 Fire Resistance

Metal panel roofs are classified as Class A to meet the model building code’s fire provisions. However, the applicable building code may require a further fire rated roof due to occupancy, construction type and space conditions. MBMA provides a list of fire-rated metal panel roofs applicable to metal building systems is available.

1.5.4 Cold Climate

Metal panel roofs have long been considered an ideal choice for cold climates because of their superior tolerance to many of the characteristics of these environments. For more commentary on this subject, refer to the following article: Design Snow Loads and Metal Buildings (December 2015). The MBMA Metal Roofing Systems Design Manual (Chapter 6 Design Practices) provides specific guidance on snow loading design.

For different climates, manufacturers will often have specific recommendations for various products, minimum slopes, and roof geometries or construction details. Proper detailing is required to prevent snow and ice from pulling flashings away from roofs, inhibiting proper drainage, and ripping gutters from eaves. Thermal movement and stress must also be addressed through proper detailing.

Metal panel roofing can shed snow unexpectedly. To prevent sudden release of accumulated roof snow, snow guards are often used. A variety of snow guard design and fastening techniques are available.

To prevent ice damming on a roof, proper detailing is key. Protective membranes can be used as a backup, if the primary waterproof plane is breached. The aforementioned snow guards can aggravate damming conditions and potential for leaks.

1.6 Industry-Specific Flashing and Metals Requirements

Generic flashing details for metal panel roofs for both low-slope and steep-slope, with and without substrates, are included in the MBMA Metal Roofing Systems Design Manual (Chapter 12 Metal Roofing Details). Included are over 80 drawings unique to metal panel roofing that address the areas of eaves, panel laps, rakes, valleys, hips, expansions joints, etc.

2. Installation Guidelines

2.1 Best Practices
2.2 Roof Weights / Re-Roof (Retrofit, Recovering)
2.3 Roof Support
2.4 Underlayment Options
2.5 General Installation Methods
2.6 Fasteners
2.7 Accessory Items
2.8 Climatic Recommendations
2.9 Eave Treatments
2.10 Bird Stops
2.11 Ventilation
2.12 Anti-Ponding
2.13 Ridge Treatments
2.14 Valley Treatments
2.15 Penetrations
2.16 Insulation
2.17 Photovoltaic and Solar Installations

2.1 Best Practices

There are a number of metal panel roofing guidelines available, some of which are noted below, available at http://www.mbma.com and http://www.metalconstruction.org. However, a manufacturer’s specific recommendations may supersede these guidelines and be more appropriate to the specific roof systems.

2.2 Roof Weights / Re-Roof (Retrofit, Recovering)

The responsibility for the structural integrity of the existing structure and its capability to support the new roof system and be in compliance with the applicable building code lies with the building owner and their structural engineer.

2.3 Roof Support

When retrofitting an existing metal panel roof, point loading of the metal deck over the roof supports must be analyzed to determine allowable loads on the roof support, and whether web crippling of the metal deck may occur under these point loads. These analyses should be performed to determine the roof support options to be used for the specific allowable load. The owner’s structural engineer must determine maximum allowable concentrated load and the maximum allowable spacing of the framing system that may occur.

2.4 Underlayment Options

Underlayment is typically not used for low-slope metal panel roof systems over open construction.

2.5 General Installation Methods

Installation should be in accordance with manufacturer’s instructions and approved installation drawings. Additionally, consideration should be given to the following:

  • SSR may be designed for thermal movements; however, proper flashing and sealing to accommodate this movement must be installed for weathertightness.
  • TFR with the exposed fasteners must include EPDM washers. Avoid over- or under-tightening the fasteners for a proper seal without damaging the rubber washers. This will help ensure a long life for the exposed fasteners securing the roof deck.
  • Roof penetrations should be located to avoid SSR, TFR and IMP seams. However, when needed it may be acceptable to locate a roof penetration at a TFR seam.
  • Avoid dissimilar materials coming into contact with metal SSR and TFR products, such as copper, lead, graphite, treated lumber, mortar, etc.
  • Direct water runoff from gutters or mechanical equipment onto metal panels may affect the panel surface.
  • Curbs and protrusions should be secured in place but allow for thermal movement according to the manufacturer’s installation drawings.

2.6 Fasteners

The fasteners should be installed securely in the locations called out on the approved construction documents in accordance with the manufacturer’s installation specifications. The correct fastener style, size, and finish should be used and the fasteners should fully/completely penetrate individual components intended to be secured. Typically, the rule of thumb would be to have three threads penetrate beyond the metal panel. Installation errors may include missing fastener heads, stripped fasteners that turn freely, improper fastener spacing and edge distances, over-driven, under-driven, or loose fasteners. Attention paid to ensuring a proper fastener finish will allow for a long service life of the product and its connection to the roof assembly. The following resources provide more detailed information:

2.7 Accessory Items

Accessories items for metal roof panel systems include items such as roof vents, curbs and jacks, access hatches, skylights and snow guards. Other examples include lightning protection, satellite dishes, antennae, service walks, rooftop lighting, security cameras, signage, photovoltaic and solar-thermal collection panels.

2.7.1 Attachment of Accessories

Installation of any roof-mounted accessory can harm the roof’s integrity, if performed incorrectly. These should be installed in accordance with the accessory and roof covering manufacturer’s installation specifications. Some key points to consider are outlined in various sections of Chapter 7 of the MBMA Metal Roofing Design Manual.

  • Be sure the accessory materials are compatible with roof materials, especially when in direct or electrolytic contact (See Section 7.5 Preventing Corrosion Problems). This is also applicable to condensation lines or other types of pipes that discharge onto a roof. Because of potential galvanic corrosion, such condensation lines should not be permitted to drain onto a roof.
  • When possible, avoid penetration of roof panels with ancillary mounting (See Section 7.7.1 Fasteners).
  • When panel penetration is unavoidable, proceed only with approved manufacturer's installation methods, and properly utilize appropriate sealants (See Section 7.7.1 Fasteners and Section 7.7.2 Sealants).
  • Do not “pin” SSR panels to the structure by mounting or installing the accessory items. For SSR applications, use approved seam clamps to avoid dual pinning and panel penetration (See Section 7.6 Thermal Movement Issues and Section 7.6 Thermal Movement Issues).
  • When adding HVAC or other curb-mounted equipment, follow the roofing manufacturer’s recommendations for their mounting the same as if it were a new roof installation (See Section 7.8.9 Preformed Curbs).

2.8 Climatic Recommendations

Significant accumulation of snow and ice may threaten the structural integrity of a metal roof system if it approaches or exceeds the design roof load capacity. In the event of severe winter conditions, the accumulation of snow and ice should be removed from the roof. Damming or clogging of gutter systems, ponding of water, or unusual drift conditions should be corrected. The following resources provide additional recommendations:

2.9 Eave Treatments

Refer to the MCA Metal Roof Installation Manual (Chapter 6 Roof Deck Substrates)

2.10 Bird Stops

Refer to the MCA Metal Roof Installation Manual (Chapter 8 Common Roof Accessories).

2.11 Ventilation

Refer to the MCA Metal Roof Installation Manual (Chapter 8 Common Roof Accessories and Chapter 10 Roofing Design).

2.12 Anti-Ponding

Refer to the MCA Metal Roof Installation Manual (Chapter 10 Roofing Design).

2.13 Ridge Treatments

Refer to the MCA Metal Roof Installation Manual (Chapter 8 Common Roof Accessories) for information regarding the direction, fastening, weather blocking, and ventilation of rigid treatments. Generic ridge details for metal panel roofs for both low-slope and steep-slope, with and without substrates, are included in the MBMA Metal Roofing Systems Design Manual (Chapter 12 Metal Roof Details).

2.13.1 Fastening

Ridge flashing requires expansion joints to prevent leaking around the screws. Follow manufacturer’s instructions.

2.13.2 Ventilation

Heat rises and, unless directed elsewhere, will rise to the highest point within the structure—generally the roof ridge. Proper ventilation in this area is important. Refer to the MCA Metal Roof Installation Manual (Chapter 8 Common Roof Accessories and Chapter 10 Roofing Design).

2.14 Valley Treatments

Generic valley treatment details for metal panel roofs for low-slope, with and without substrates, are included in the MBMA Metal Roofing Systems Design Manual (Chapter 12 Metal Roof Details).

2.15 Penetrations

Roof penetrations should be kept to a minimum and should be located within the flat of the panel where possible, as opposed to near seams. Penetrations that cut through the seam of the panel are a potential source of water infiltration and may compromise the structural integrity of the panel. If it becomes necessary to place a penetration through a seam, a customized roof curb should be used to ensure the weathertightness of the roof system. Consideration should be given to thermal expansion and contraction of the roof system when sizing the roof penetrations. All required roof penetrations must be coordinated with the roof system installer. For more information on roof penetrations, refer to the MBMA Metal Roof Systems Design Manual (Chapter 7 Installation & Maintenance).

2.16 Insulation

There are a variety of insulation types and methods available for low-slope metal panel roof systems. These are based on the type of construction and whether there is a roof substrate. The intent is to insulate the building from the effects of the outside environment, while keeping the inside temperature at the intended level. It is important the insulation be installed correctly with the vapor retarder located on the appropriate side of the roof (this is dependent upon the climate location in the country) to avoid condensation. For more information on this topic, refer to the following resources:

2.17 Photovoltaic and Solar Installations

Low-slope SSRs provide the optimal foundation for photovoltaic (PV) and solar installations, since the roof is expected to last longer than the system it supports. Attachment of PV panels to an SSR is more straightforward than with other roof types since clamps can be installed directly to the ribs of the metal panels. As a result, no penetrations are introduced to the metal panel roof system.
For a detailed review of PV panels on low-slope metal panel roofs, refer to the MBMA Energy Design Guide for Metal Building Systems (Appendix A Photovoltaic Roof Panels). An additional reference on the topic includes the ASCE Guidelines for Snow Loads on Solar Paneled Roofs. This guide discusses the potential effects of solar panels on a roof that may change the exposure of the roof, increase the potential for sliding loads and possibly act as obstructions behind which snow drifts can form.

3. Repair and Maintenance

3.1 Natural Aging vs. Damage
3.2 Individual Panel Replacement
3.3 Installing Different Panel Designs
3.4 Warranty vs. Non-Warranty Items
3.5 Locating Product Sources
3.6 Disposal / Recyclability of Products
3.7 Dents and Paint Flaking
3.8 Maintenance and Upkeep Guidelines

Metal panel roofing systems are designed to withstand most severe weather conditions, and provide maximum years of protection with minimal maintenance. However, no roof is completely maintenance-free or immune to the continuing effects of weather. Routine maintenance should follow manufacturer’s recommendations and include protecting the roof from excessive foot traffic, keeping corrosive agents off the roof panels, restoring sealants around roof openings and keeping the roof free of debris. Often, the accessories can be replaced inexpensively, thus extending the life of the roof service.

3.1 Natural Aging vs. Damage

A low-slope metal panel roof may last over 40 years with little to no maintenance. Occasionally, cleaning may be needed. On a painted roof, abrasive or chemical cleaners will damage the painted finish and should not be used. A mild household cleaner may be effective in some cases. Refer to the MBMA Metal Building Systems Manual (Appendix A11 Cleaning Panel Surfaces) for guidance on cleaning metal panel surfaces. If the product needs to be recoated, the affected area should be cleaned and reprimed before being repainted.

Small scratches that do not penetrate the zinc-aluminum coating or the zinc coating (i.e., no apparent rust) do not require touch-up paint. If touch-up is required by the owner or architect, touch-up should be done by using an artist paint brush to apply color-matched touch-up paint obtained from a reputable supplier. Refer to the MBMA Metal Roofing Systems Design Manual (Chapter 7 Installation & Maintenance) for more information on surface damage. Additional information may be found the MCA Metal Roof Installation Manual (Chapter 17 Maintenance).

3.2 Individual Panel Replacement

Information may be found the MCA Metal Roof Installation Manual (Chapter 17 Maintenance).

3.3 Installing Different Panel Designs

Information may be found the MCA Metal Roof Installation Manual (Chapter 17 Maintenance) and MCA Technical Resources Roof Covering Repair Requirements and the International Code.

3.4 Warranty vs. Non-Warranty Items

Most metal panel roofing products will have a paint or a coating warranty and some products may even have weathertightness warranty.

3.5 Locating Product Sources

The Metal Roofing Alliance provides a resource to obtain a roofing contractor in the project location area.

3.6 Disposal / Recyclability of Products

Metal panel roofing is 100% recyclable and may be disposed of at any local metal scrap facility. For more information on the recycling and recyclability of metal panel roof products, its contributions to the environment, and green building code provisions, go to MBMA Energy Design Guide for Metal Building Systems (Chapter 9 High-Performance Green Building Codes, Standards and Rating Systems).

3.7 Dents and Paint Flaking

Painted metal panel roofing can suffer from small dents and scratches due to hail or during routine maintenance. The paint systems used today are robust and tough enough to protect from paint flaking. The National Coil Coating Association provides more information on Assessing the Damage Resistance of a Coating in their Toolkit #22 document. One of the many advantages of metal panel roofing is that it does not lose its impact resistance as it ages. Small dents from hail, where the paint has not been cracked or flaked off, typically will not affect the weatherability or structural performance of metal panels. If the paint is cracked or flaked, corrosion could occur. In those cases, refinishing or replacement should be considered.

3.8 Maintenance and Upkeep Guidelines

The MBMA Metal Roofing Systems Design Manual (Chapter 7 Installation & Maintenance) offers a number of recommendations for maintenance and upkeep of metal panel roof systems.

3.8.1 Cleaning Metal Roof Products

Due to the nature of the smooth metal panel roof products, valleys are primarily self-cleaning each time it rains. Algae, moss, dirt and foliage typically flow off a metal roof in the event of rain.
A mild household cleaner may be effective in some cases. Refer to the MBMA Metal Building Systems Manual (Appendix A11 Cleaning Panel Surfaces) for guidance on cleaning metal panel surfaces. If the product needs to be recoated, the affected area should be cleaned and reprimed before being repainted. Excerpts from Appendix A11 have been provided below:

In many cases, simply washing the building with plain water using hoses or pressure sprays will be adequate. In areas where heavy dirt deposits dull the surface, a solution of water and a detergent (1/3 cup per gallon of water for example) may be used. A clear water rinse should follow.

Mildew may occur in areas subject to high humidity, but it is not normally a problem due to the high inherent mildew resistance of the bare panels or painted panel finishes. However, mildew can grow on dirt and spore deposits in some areas. To remove mildew along with the dirt, the following solution with a clear water rinse is recommended:

  • 1/3 Cup detergent
  • 2/3 Cup tri-sodium phosphate (TSP)
  • 1 Quart sodium hypochlorite 5% solution (liquid household bleach)
  • 1 Gallon water

Solvent and abrasive type cleaners should be avoided. Oil, grease, tar, wax and similar substances can be removed with mineral spirits applied only to the areas that are contaminated. Follow up the use of solvents with detergent cleaning and clear water rinsing.

Metal shavings from drilling and other work on the roof should be carefully removed by brushing or sweeping at the end of each day during erection. Shavings left on the roof will quickly rust and can stain the roof finish. Removal of rust stains is very difficult. On a painted roof, any abrasive or chemical cleaners will damage the painted finish and should not be used. A mild household cleaner may be effective in some cases.

Stains on galvanized or aluminum-zinc roof may be removed using a non-metallic abrasive pad.

3.8.2 Walking on Product

When walking on metal roof panels, the following safety guidelines—excerpted from the MBMA Guide for Inspecting Metal Building Systems (Chapter 6 Metal Roof and Wall Systems) be adhered to:

  • Metal roof panels may contain a manufacturing lubricant that can be extremely slippery. The Voluntary Lubricant Compliance Program for Steel Deck and Roofing provides guidelines to reduce the level of lubricant when manufacturing metal roof panels. For more information, refer to the MBMA Metal Building Systems Manual (Appendix A13 OSHA Steel Erection Regulations).
  • Never step or walk on the major rib of a panel. Always walk within the flat part of the panel.
  • Never step, stand, sit, or place material/equipment on skylights.
  • Never walk, stand, or sit on an unsecured metal roof panel. The panel could buckle or collapse causing serious or critical injury.
  • Never walk, stand, or sit on a curbed or non-curbed skylight, or on in-plane translucent panels. Translucent panels often include the same ribbed profile as the metal roof panels. As a result, be aware of the location of all skylight and translucent panels on a roof.
  • Appropriate fall protection procedures must be followed.

    3.8.3 Roof Penetrations and Skylights

    Roof penetrations and skylights on a metal panel roof may need to be annually inspected and resealed as needed. When replacing or sealing, ensure the compatibility of the product with the primary seal used on the metal panel roof. Silicone may not be compatible. Refer to the MBMA Metal Roofing Systems Design Manual (Chapter 7 Installation & Maintenance), as well as the MCA Metal Roof Installation Manual (Chapter 7 Panel Connections), for more information.

    3.8.4 Expected Product Lifecycle

    Often, the lifecycle of metal panel roofs extends to 40 years and beyond. In fact, certain metal panel roof systems can have a service life of at least 60 years, according to the Metal Roof Service Life report sponsored by MCA and the ZAC Association. This report focused on the service life of unpainted 55% Al-Zn low-slope standing seam metal panel roofing in a wide range of environments across the U.S.

4. Damage Issues

4.1 Determining Hail Damage
4.2 Determining Wind Damage
4.3 Fire
4.4 Cold Weather

In the event a low-slope metal panel roof needs to be repaired, it is recommended that the same metal panel profile be used to ensure proper weather protection with joints and seals. If the damage warrants a complete re-roofing, a retrofit metal roof system may be applied on top of an existing sloped or flat roof by using a cold-formed steel framing system to achieve a new sloped roof. This provides a weathertight system. More information may be found in the MBMA Metal Roofing Systems Design Manual (Chapter 4 Retrofit). Caution should be used for applications of a non-metal roofing retrofit system, such as single-ply membrane roofing, for short-term and long-term reasons, including weatherability, water flow, load compliance and warranty continuation.

4.1 Determining Hail Damage

Hailstorms may cause aesthetic damage to a metal panel roof but the integrity of the metal roof is typically maintained. If damage occurs to the coating of the metal panel, then corrosion could occur. See 3.7 Dents and Paint Flaking for additional discussion.

4.1.1 Repair or Replacement

Deciding whether to repair or replace the roof following a hail event requires an in-depth evaluation of the condition of the metal panel roofing, including a review of the existing design limits and an overall inspection to ensure there are no missing parts of the existing roof. If the condition is determined to be adequate, then re-roofing could be performed. If a metal panel roof needs to be re-roofed or repaired, refer to the appropriate sections within the MBMA Metal Roofing Systems Design Manual, and the MCA Roofing Installation Manual.

4.2 Determining Wind Damage

Wind damage to roof insulation and coverings usually begins at or near the windward edge, particularly at the corners, and progresses inward. The metal panel roofing or trim will pull away from the structure.

4.2.1 Repair or Replacement

When wind damage occurs, primary consideration should be given to removing the damaged, wet, or deteriorated materials and making temporary or permanent repairs as quickly as possible. The permanence of repairs will depend on the nature and extent of damage. If a metal panel roof needs to be re-roofed or repaired, refer to the appropriate sections within the MBMA Metal Roofing Systems Design Manual, and the MCA Roofing Installation Manual.

4.3 Fire

Metal panel roofing is noncombustible; however, a fire within a building could lead to structural damage. More information on repair and replacement may be found in the MBMA Fire Resistance Design Guide for Metal Building Systems (Chapter 2 Fire Protection and Safety).

4.3.1 Determining Fire Damage

Besides the evident fire damage of combustible material, a fire may affect the metallurgy and properties of steel material. These effects could be temporary if the steel is subject to only moderately high temperatures. The extent of the deflections and distortions caused by the fire heating the steel roof and substructure will vary. Cold-formed steels are more susceptible to damage in high-heat fire conditions. Steel exposed to high temperatures may be permanently distorted, as the mechanical properties of the steel are changed. In these cases, the steel product will likely need to be replaced. A specialty engineering consultant should be engaged to evaluate the extent of the fire damage and to determine what remediation is necessary.

4.3.2 Repair Vs. Replace

Consideration for repair or replacement should include the nature, severity and duration of the actual fire event, as well as the amount of visible damage to the materials.
If a metal roof needs to be re-roofed or repaired, refer to the appropriate sections within the MBMA Metal Roofing Systems Design Manual, and the MCA Roofing Installation Manual.

4.4 Cold Weather

Metal panel roofs should be designed to meet the snow load provisions of the applicable building code, including the effects of drifting snow. Sliding snow and melting snow should also be considered. For more information on the subject, refer to the MCA Technical Bulletin Metal Roof Design for Cold Climates. Additionally, refer to the FEMA Snow Load Safety Guide. This guide provides information about preventative measures to take before the snow season, and suggests actions that should be taken before, during and after a snow event.

4.4.1 Repair Vs. Replace

Metal panel roofing and its substructure can deflect significantly under extreme load, but then return to its original state when the load is removed. If the panels or substructure exhibits permanent distortion after the load is removed, replacement is typically warranted. Normally, it is impractical to repair damaged metal panels or substructure. If a metal roof needs to be re-roofed or repaired, refer to the appropriate sections within the MBMA Metal Roofing Systems Design Manual and the MCA Roofing Installation Manual.

5. Industry Resources

5.1 Industry Associations
5.2 Technical Bulletins/Installation Guides
5.3 Technical Support Contacts and Member Lists
5.4 Contractor List for Regions

Additional industry resources may be found at the following websites:

5.1 Industry Associations

5.2 Technical Bulletins/Installation Guides

Metal Building Manufacturers Association resources:

Metal Construction Association resources:

National Coil Coating Association resources:

American Society Civil Engineers resources:

American Iron and Steel Institute resources:

ASTM International resources:

Federal Emergency Management Agency resources:

FM Global resources:

Underwriters Laboratory (UL) resources:

5.3 Technical Support Contacts and Member Lists

Technical support contacts and member companies may be found on the following websites:

5.4 Contractor List for Regions

The Metal Roofing Alliance provides an online resource to locate roofing contractors near a project location.

Cedar Bureau Roofing

Benefits of Cedar

Fasteners and Non Permeable Barrier

Cedar Bureau Sidewalls

Installation Video

Grading and Inspection

Disclaimer: This manual has been prepared for informational purposes only. RICOWI, IBHS, and the participating roofing industry organizations expressly state that they have no liability, in negligence, tort, or otherwise, with respect to the use of any of the information and/or practices described in this article. The information set forth in this manual is provided in good faith. The user assumes the sole risk of making use of the information provided in this manual.

Users of this manual are strongly urged to follow accepted safety practices, refer to applicable local building codes and standards, and relevant manufacturers’ instructions for appropriate technical requirements, and to work with a qualified professional in order to operationalize the information contained herein. Photographs and examples contained in this manual are provided for illustrative purposes only and do not guarantee the condition of any specific product or the effectiveness of any repair or installation. Nothing contained in this manual is intended or written to be used, nor may it be relied upon or used, by any person and/or business as legal advice.

NOTE: The manual is being completed in sections, and will be released in stages. Check back often to see the most up-to-date edition of the guide.
Please report broken links or other issues to Simon Kellogg (skellogg@ibhs.org).