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TECH TALK: March 2026

 

Re-roof assembly options are influenced by a variety of factors, including existing roof condition, deck type, building occupancy, customer budget, and other project-specific variables. Each of these elements plays a role in determining the most appropriate system. Fortunately, Carlisle remains the industry leader in innovative products and systems that provide contractors with reliable solutions and a competitive advantage.

Carlisle offers numerous warrantable systems for overlaying existing roofs. Examples include adhered coverboard with bareback membrane over gravel BUR; mechanically attached coverboard with adhered bareback membrane over existing single-ply systems; mechanically fastened coverboard with RhinoBond plates and fasteners paired with bareback TPO over existing modified bitumen; restoration coating systems; and more.

This article will review FleeceBACK overlay opportunities over existing single-ply and aged modified bitumen roofs.

Preparation

Carlisle will accept FleeceBACK EPDM, TPO, or PVC to be adhered directly to an existing EPDM, TPO, or aged mod-bit system. The existing roof must be assessed thoroughly and prepared per Carlisle’s Specification. Please refer to the General Design Considerations in Carlisle’s FleeceBACK section of their Specification and Detail Book:

System Option #1 – FleeceBACK over Aged Mod Bit

 

Carlisle will accept FleeceBACK EPDM, TPO, and PVC to be installed directly over an existing asphaltic roofing system.  There are a wide range of aged, modified asphalt systems that this system can be installed over.

Although it is an excellent solution for an overlay, it should be noted that any failure of the existing system is not considered a warranty claim. This should be taken into consideration when determining if the existing roof is a good candidate for an overlay.

Some existing asphaltic systems, like Gravel BUR, will require a separator board since the membrane cannot be installed directly over the gravel even after it has been prepped. Please refer to the table on the right which reviews the acceptable roof types and requirements for each existing modified asphaltic roofing system type.

 

System Option #2 – Fleeceback over Aged Single Ply (EPDM & TPO)

Aged Single Ply can also be overlaid with FleeceBACK membrane after proper preparation. Carlisle will accept all FleeceBACK Membranes to be adhered directly over TPO & EPDM Membranes (PVC is not allowed). There are a few other things that should be noted when going over an existing single ply:

  • The membrane color of the FleeceBACK membrane must match the existing system

  • Membrane must be power-washed and allowed to dry

  • Existing single ply system OR new FleeceBACK membrane must have mechanical securement at the perimeter in lieu of a double bead application of Flexible FAST adhesive.

Benefits of FleeceBACK Overlay

  • Non-penetrating, low noise, no odor

    • Quieter installations over occupied buildings with tenants

    • Excellent solution when installed over roofs with concrete decks

  • Flexible Fast is VOC Free

    • No harsh odors entering occupied living spaces

  • Additional R-Value provided by the Flexible Fast Adhesive

  • 33% - 50% greater puncture resistance than greater membranes

  • 33% - 66% increased hail protection

  • Overlay roofing systems minimize disposal and landfill costs

  • Increased productivity on the roof

  • Excellent Warranty Offerings

    • Up to 20 Year NDL

    • Up to 80 MPH Windspeed Warranty

    • Accidental Puncture Coverage Warranties (No additional charge)

    • Manufacturer Hail Warranties (No additional charge)

If you have any additional questions regarding FleeceBACK membranes or any of the systems mentioned in this article, please feel free to reach out to Dane Helnore at CSL West.

 

 
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