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Metal Over Low Slope Retrofit – Standing Seam Metal Roof System
Convert low-slope roofs into long-life metal systems with engineered framing and minimal disruption.
McElroy Metal’s Flat & Low-Slope Roof Retrofit System adds slope and drainage over existing roofs using light-gauge framing—eliminating tear-off, ponding, and ongoing membrane failures. The result is a durable, energy-efficient metal roof that installs quickly, improves performance, and delivers decades of low-maintenance service.
Metal Over Low Slope Ideal Applications
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Commercial, industrial, or institutional buildings with flat or very low-slope roofs (often ≤ 1/4:12) in need of replacement.
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Facilities where roof downtime or interior disruption must be minimized.
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Buildings where improved drainage, reduced maintenance, and long-term asset value are priorities.
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Structures with existing roofing systems (membrane or metal) that remain in good structural condition and can accept retrofit framing.
Metal Over Low Slope Top 3 Benefits
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Metal Over Low Slope: Metal retrofit systems routinely deliver 50+ years of service life—far exceeding conventional membrane roofs and reducing long-term maintenance costs.
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Enhanced Curb Appeal & Sustainability: Transforms outdated flat roofs into clean, modern rooflines that improve property value and reduce landfill waste compared to traditional tear-offs.
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Solar-Ready Design: The metal roof surface provides an ideal platform for solar PV integration and future building upgrades.
Low Slope Retrofit Roofing Systems
McElroy Metal Retrofit Roofing Systems provide long-term life expectancy and reduced life-cycle costs. In many cases, the cost difference between a conventional roof tear-off and replacement compared to a retrofit metal roof system is a return on investment which can be recouped in just a few short years. As an added plus, McElroy Metal Retrofit Roofing Systems provide curb appeal which simply cannot be achieved with flat roofs.
Building Owner Benefits
- Decades long service life
- Reduced maintenance
- Energy savings through reduced consumption
- Metal roofing is an ideal host substrate for solar photovoltaic panels
- Increases wind and snow storm resistance
- Possible reduction of insurance premiums
- Improves value of your building
The Contractor’s Advantages
- Easy to erect framing systems
- Designed by in-house McElroy Metal engineering staff
- Proven and tested standing seam metal roofing systems
- All materials manufactured by McElroy Metal
- Quicker than normal turn-around times
- Reduces landfill expenses for disposal of existing materials
Additional Information
McElroy Metal Retrofit Roofing Systems are engineered to adapt to the existing roof’s structural support system whether constructed of steel, concrete or wood. The importance of engineering the new retrofit framing system is hallmark to the overall project.
Download The McElroy Metal Retrofit Roofing Guide to Learn More
Common Retrofit Assemblies
The most common framing assembly for a metal roof retrofit is the Post and Purlin system. As shown in the following illustrations, the system can be employed for installation over existing roofs with steel or wood framing as well as structural concrete systems.
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The metal roof retrofit system is installed over steel bar joists that are spanning parallel to the new roof slope. |
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Adaptation to Steel The Post and Purlin system adds a continuous base zee, which enables it to be installed over steel bar joists that are spanning perpendicular to the new roof slope. |
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Adaptation to Wood For existing buildings with wood framed roofs, the Post and Purlin system uses a continuous base zee installed perpendicular to the existing wood joist. The base zee is required for these types of roofs, regardless of joists' span direction. |
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Adaptation to Concrete For structural concrete roofs on existing buildings, the Post and Purlin system uses base shoes and posts that are installed centered over the existing concrete beams. When the beams span perpendicular to the new roof slope, a base shoe is still used, dependent on the spacing of the beams in relation to the retrofit purlin's span capacity. Otherwise, a continuous base zee would be included in the system. |
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Similar in concept to the Post and Purlin system, McElroy's Wide-Span framing system offers a unique method for specific applications where the existing roof's primary support systems are parallel to the new roof slope. In this illustration, a continuous base zee is placed directly over the existing primary framing (beam or load-bearing walls). Adding a continuous zee rafter supported by posts that are installed directly over each existing joist, will enable the new zee purlins to be placed as needed to satisfy design wind and snow loads. This system can easily be designed for purlin spans up to 30'-0" using 6" to 10" deep zee purlins. |
Weathertightness Warranties
If your project requires a Weathertightness Warranty and you don’t already have a job specific Pre-Approval Form issued by McElroy Metal, click the button below to get started.
Shop Drawing Service
Running short of time to complete your own shop drawings? McElroy Metal can help. Click the button below to provide us some basic information and we’ll be in touch soon to discuss your project specifics.
Download Shop Drawings
If you’re creating your own shop drawings, click the button below to gain full access to our CAD and PDF Files.
Notes & Manufacturing Locations
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Existing structures must be inspected and confirmed to be in satisfactory condition before retrofit framing is designed and installed.
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Inquire for other gauges and substrates; minimum quantities may apply.
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Oil canning is a natural occurrence in metal panels and not a cause for rejection.
Why Choose McElroy Metal
McElroy Metal is an employee-owned manufacturer with more than six decades of experience producing high-quality metal roofing, wall systems, and substructural components. Our nationwide manufacturing and service center network ensures consistent availability, responsive support, and dependable delivery. Built on a culture of craftsmanship and partnership, our products are engineered for long-term durability and trusted performance on projects of every size.
Find a Distributor / Contractor Near You
Whether you’re building a new home or planning renovations, a metal roof can deliver long-term cost savings and comfort. To explore your options and find the product that meets your aesthetic and budgetary needs, contact a McElroy Metal distributor or contractor in your area today. We can’t wait to help make your dream home a reality.
Frequently Asked Questions
The questions below address common considerations and help guide product selection for your project.
Metal Over Low Slope Articles
