Menu Call The Metal Roof Specialists
Put your Trust In Us. An industry leader in Metal Roof Systems since 1968.
Call The Metal Roof Specialists
Request a No-Cost Inspection Get a No-cost Inspection
Home / Reroof/Retro-fit


There comes a time in the life of every roof system when replacement or retrofitting is a necessity or analytically cost based decision.  This can be due to a number of factors that include:

  • Expiration of useful life -depletion of protective (i.e. sacrificial or barrier) metallic coatings or manufacturer applied paints on aged metal panels and the subsequent deterioration of the base material
  • Premature roof system failure (i.e. inadequate: drainage, detail or design, improper repairs with non-conforming techniques / non-compatible materials, ineffective preventive maintenance, contractor and/or employee abuse, improper installation of flashing and curbs, and “out of module” panels, inferior: panels, trim components, sealants and fasteners, etc.)
  • Premature roof insulation failure – this is usually directly associated with a poorly functioning roof devoid of a preventive maintenance program
  • Upgrading for energy conservation and/or building code requirements
  • Storm damage
  • Aesthetics, etc.

Framing and new SSR galvalume metal roof over old BUR

Older galvanized metal roofing, exceeding 40 years of age, have a tendency for the manufacturer metallic coatings or factory applied paints to deplete or wear off over this span of time.  And in many cases the application of a protective industrial coating may not be beneficial or practical due to the degree of deterioration.  Considering the fact that recent studies have substantiated the longevity claims for galvalume SSR roof systems, and the reality that enhanced energy efficient insulating system technologies are available, life cycle cost analysis often recommends this option.

Premature roof system failure is often the result of neglected preventive maintenance in concert with improper roof repairs that incorporate non-conforming techniques and non-conforming materials.  This inadequate action to roof system deficiencies over extended periods of time, not only exacerbate the original moisture infiltration issue but also accelerate sub-surface (i.e. hidden) component and insulation damage and failure.

Energy conservation as related to commercial buildings is at an elevated state of focus these days.  It is not only a practical matter that we consider the use of new materials and technologies that improve energy efficiency in our building envelope, it may also provide an enhanced ROI and the system integrity / longevity desired.  The U.S. uses approximately 25% of the total energy produced in the world today.  We also use about 21 million barrels of oil a day for transportation, industrial and commercial use.  Commercial building heating and cooling costs amount to approximately 40% of the energy used in the operation and function of these facilities.  A majority of the thermal losses are, of course, through the roof system.  Heat transfer through the roof system will be at an accelerated rate if the insulation system has been compromised by excessive moisture infiltration or the aged insulation system is thin (low R-value) and/or unabated air flow is allowed to permeate the building envelope through roof components, roof to wall transitions, and at equipment cavities.

Over the last 30 + years new and improved galvalume SSR metal roof panel systems, with hidden attachment assemblies, have revolutionized the building industry through an extension of life expectancy, significantly reduced opportunity for water infiltration, thermal cycling and a freedom of movement,  and the availability of improved insulating systems.

New studies are revealing that the galvalume SSR panels can outlive the useful service life of some buildings and can be expected to function for 80 or more years with proper, routine inspections, and appropriate preventive maintenance.

Galvalume SSR Statistics

Galvalume SSR Panel Study by Ron Dutton

“In conclusion, the data from this project support the proposition that a Galvalume SSR system could be installed today on new or retrofit low slope roof systems in a wide range of environments and not require replacement during the building’s entire service life. Of course, proper roof inspections and maintenance associated with roof ancillaries would still be required, as they are with any other roof system. But the projected service lives demonstrated in this study clearly demonstrate the sustainable benefits of using Galvalume-coated steel roof panels for new and retrofit applications.”

Galvalume SSR Longevity Study

Selecting the Right Finish for Metal Roofing:

Combination Sacrificial / Barrier Coatings [Galvalume]
“Galvalume finishes were introduced nearly 30 years ago and provide both galvanic and barrier protection.  The finish includes zinc and aluminum.  The zinc (approximately 45% by weight) provides the sacrificial protections, and the aluminum (55% by weight) provides the barrier protection.  This hybrid finish has become extremely popular for low slope (less than 3:12) roof applications.  In 1995, it was reported that over 5 billion square feet of Galvalume roofing panels had been installed since its introduction.  Due to the combination of protection mechanisms, this finish has the ability to provide longer service life that a galvanized finish in the same exposure.  Current marketing literature suggests a service life of 30 years or more in most environments, without major maintenance.”

By Derek A. Hodgin, P.E., RRO, RRC
“Selecting the Right Finish For Metal Roofing,
Part I: Metallic Coatings,” Metal Roofing.
August 2001

An Introductory Overview of Green/Sustainable Retrofitting of Existing Buildings in the U.S.

Executive Summary

“The word “Retrofit” today, has many connotations when used in the current Green Marketplace for Building Energy improvements. While there are a multitude of retrofit methods and concepts employed in existing buildings to achieve energy savings, most do not provide significant savings in either the short-term or long-term. However, there is one retrofit method that provides substantial and continual energy savings with long-term service life and the opportunity to employ renewable energy technologies. The method is “Retrofit Re-roofing with Metal”.

The Department of Energy estimates that 25% of our buildings have poorly insulated and maintained roofs making them immediate candidates for high performance retrofit re-roof applications. Furthermore, the DOE’s Building Technologies Program (BTP) identified residential and commercial buildings as the largest energy consuming sectors, accounting for about 40% of the total U.S. annual energy use2. In addition, the BTP found that between 24-30% of these sectors’ energy loads are from thru-roof heat gain/heat loss and air infiltration. You may say that a significant portion of our energy costs is “Going through the Roof”.”

“Key Facts

Retrofit Metal Re-roofing provides design professionals and building owners with solutions for the following:

  • Reduces energy demand and substantially improves our energy efficiency and dependence on oil.
  • Creates Jobs in the construction, design and metal components manufacturing areas as well as the renewable solar energy market.
  • Roof maintenance for flat roofs as compared to metal roofing is greatly reduced by as much as 40-50%.
  • Land fill infiltration of flat roof tear offs is eliminated and cost of land fill management is improved.
  • Metals (Steel and Aluminum) are fully recyclable and achieve LEED points for existing building certification.
  • Metal roof systems offer the building owner reduced insurance premiums for their catastrophic wind and hail resistant qualities.
  • Retrofit metal roof systems are professionally engineered to meet all governing national and local building codes. “

Metal Building Article: Retrofit Roof Solutions

Knowing the typical profile, evaluate the suitability of various metal roof solutions. First, existing conditions must be thoroughly investigated and evaluated. Corrosion on top and bottom panel surfaces is a large concern. The integrity of the panel-to-purlin attachment must be evaluated.

Warning: An obvious fall hazard exists at the edge of a roof, and less obvious fall hazard exists at the interior of the roof. The interior roof hazard is the potential to fall through a rusted, deteriorated metal panel or a skylight. Roof coatings conceal roof panel deterioration and translucent fiberglass panels.

The thickness condition and location of any existing insulation and vapor retarder should be investigated. The presence of any moisture in the insulation and/or the bottom side of the R-panel should be noted. A dew-point analysis based on the building usage should be performed to determine the proper amount of insulation required and location and required perm rating of the vapor retarder.

PEMBs are optimized for the original, code-required loads and do not provide for the added dead load of any future roofing materials. Reroofing a PEMB should include a structural analysis of the current system by a qualified engineer familiar with PEMB design assumptions and construction. Changes in American Iron and Steel Institute cold-Formed Steel Design Manual 2002 Edition, have reduced the capacity of cold-formed steel purlins from the 1980, 1986, 1996, and 2001 editions. Existing purlins that worked using earlier editions will not support the same loads when designed with the current edition.

Model building codes include very little about retrofitting metal roofs or metal buildings.  The 1997 Uniform Building ode contains a chart in the "Appendix to Chapter 15 - Reproofing" indicates an existing metal roof only can be retrofitted with another metal roof. This restriction can be explained by considering the adequacy of a 26-guage R-panel or 24-gauge standing-seam roof panel as a supporting, structural deck for the application of any conventional roofing materials. Conventional roof warranties contain exclusions for "excessive building or structure movement".

Tear off and replacement of a 26-guage R-panel roof with another metal roof adds little of any weight. A through-fastened R-panel roof cannot be replaced directly with a standing-seam metal roof. The PEMB purlin design takes advantage of the through-fastened R-panel roof to help brace the purlin top flange. The through-fastened R-panel roof might have been used as a wind diaphragm similar to a structural roof deck. A standing-seam roof will not brace the top flange of the purlins not act as a wind diaphragm.

Safety is a consideration while working over open purlins during tear-off and replacement. Building contents and/or operations are susceptible to damage and/or interruption because of weather. A new R-panel roof can replace the old R-panel roof without affecting the existing PEMB design. To evaluate a tear-off and replacement solution using a standing-seam roof, qualified engineer should check the PEMB design.

A roof coating adds minimal weight to an existing roof and can be applied with spray equipment, by brush or by paint roller. Coatings come in a variety of colors with bright white being solar reflective, providing an energy benefit in the summer cooling months.  Most coatings have good flexibility and elongation to accommodate movement and thermal stress. There are many different types of coatings to address leaks and rusting of metal panels. Acrylic-based elastomeric coatings are popular for addressing leak problems, and asphalt-based coatings containing aluminum are popular as rust inhibitors.

(Coatings applied over skylight panels or deteriorated steel panels can create a fall safety hazard for foot traffic on the roof.)

The condition and surface preparation of the existing panel can affect the adhesion of the coating. If a coating loses adhesion, the resulting separation of the coating from the panel surface can allow moisture to become trapped, resulting in accelerated rusting of the existing panel. Surface preparation for the application of coating requires all foreign materials (sealing products, previous coatings, metal oxidation, loose paint, etc.) to be

fully removed. The applicator must be skilled in the proper application methods for the coating and allowable environmental conditions, including temperature, humidity and wind.  Most coatings can accommodate uniform panel movement. Movement concentrated at panel lap joints and flashings can exceed a coating's allowable elongation. Excessive vertical deflection from live loads or even horizontal deflection from wind loads can damage the coating. Coatings will not span over holes or gaps in the panel. This can be addressed by embedding a reinforcing fabric in the coating.  Reinforcing fabrics have little elongation, reducing the elasticity of the coating system.

Single-ply membrane roofs (EPDM, TPO, PVC, etc.) are available as fully adhered and mechanically fastened applications. A reinforced single-ply membrane can be installed over an existing metal roof fastened to the underlying purlins or existing 26-guage R-panel. A qualified engineer should verify the design and attachments if the single-ply system to the PEMB. Using the 26-guage R-panel roof as the only attachment for a single-ply membrane overlay is not recommended and may void the single-ply roof warranty.

When the single-ply membrane sheet is mechanically fastened to the purlins, the sheet width should be 5 to 6 feet (1.5 to 1.8 m) Unreinforced single-ply membranes provide as much as 200 to 300 percent elongation, however, reinforced membranes provide 10 percent or less elongation, which must accommodate the expected thermal and wind movement of the PEMB and R-panel.  Single-ply membrane systems are relatively easy for contractors to install and require little or no specialized equipment. White membranes are reflective, providing an energy benefit in summer months. However, dirt accumulation can negate this benefit.

A single-ply membrane overlay uses rigid board insulation. (1- to 1 ½ inch 25 to 38 mm thick based on R-panel rib height) to fill the area between the ribs of the R-panel. A continuous layer of rigid insulation is applied over the panel ribs and fastened to the R-panel or purlin with insulation plates and screws. Using polystyrene insulation can affect the roof fire rating. Wood blocking is installed at roof edges to secure the roof flashings and membrane terminations. The weight if a single-ply overlay, including 1 ½ inches (64 mm) of rigid insulation, is about 1.25 pounds per square foot (psf).


“Roof Hugger” sub-purlin framing system

What Is Metal-over-Metal Re-roofing? [i.e. Retro-fit Roofing]

Simply put, it is the installation of a new long life metal roof over an existing metal roof in a way that is structurally correct, non-disruptive and cost effective. It is a system that adds strength, is environmentally friendly, cooler in summer, warmer in winter and conserves energy.

ROOF HUGGER provides the industry’s most effective way of doing this with ROOF HUGGER SUB-PURLIN SYSTEMS. The Roof Hugger Systems can fit ANY existing metal panel, support ANY new roof panel and be configured to add insulation and solar energy equipment between the old and new roofs.

Roof Hugger patented sub-framing systems for Metal-over-Metal re-roofing applications provide the Building Owner, Design Professional and Roofing Contractor with a multitude of benefits and advantages:

Building Owner Benefits

  • Old Roof Stays - No Business Disruption
  • Insulation is Easily Added for Energy Savings
  • 40+ year New Roof Service Life
  • New Roof can have 20-Plus Year Weathertight Warranty
  • Easy Upgrade from Screw-down to Standing Seam
  • Meets New Stringent Building Code Requirements
  • Available Solar Energy Systems

Design Professional Benefits

  •  Expert Online AutoCAD Details
  • Factory Mutual & Florida Product Approved Assemblies
  • Extensively Tested for ASTM-1592 Wind Uplift
  • Meets Building Code Requirements
  • Free Preliminary Design Load Estimates
  • Can Compensate for Added Retrofit Weight
  • American Made with 16ga. 50KSI, G-90 Steel
  • Custom Depths for Increased Insulation
  • USGBC LEED Point Applicable
  • Ideal Platform for Renewable Solar Systems

Roofing Contractor Advantages

  • Labor Saving - Minimal Prep Time
  • Precision Pre-Punched for Anchoring
  • Low Profile - Structurally Correct
  • Zee Shape - Best for Screw-down Roofs
  • Free Preliminary Design & Estimates
  • 2-Day Shipping on In-Stock Components
  • Fast Project Completion
  • Growing Market Sector

National Roof Coaters believes in and promotes cost effective roof audits, routine preventative maintenance and remedial repairs with follow up service to preserve long lasting metal roof systems. These actions prolong roof life and preclude large, premature capital expenditures. However, when conditions dictate that replacement or retro-fitting is the only alternative National Roof stands to serve you.

Let National Roof Coaters provide you with a professional assessment of your existing metal roof system, and assist you in the data driven decision making process in evaluating re-roof or retrofit roof alternatives.