Modified Bitumen

Modified Bitumen (MB) sheet membranes have been in use in the United States since the mid-1970s. Modified roof membranes are composed of reinforcing fabrics that serve as carriers for the hot polymer-modified bitumen as it is manufactured into a roll material. MB roof system membranes are composed of multiple layers, much like BUR membranes. MB roof systems typically are installed as a two-ply system and almost always are fully adhered.

There are two types of MB roofing membranes:

  • SBS polymer-modified bitumen membranes commonly are installed in hot moppings of asphalt (similar to BUR systems) or cold adhesive. Some SBS modified membranes are self-adhering; that is, they contain an adhesive backing.
  • APP polymer-modified bitumen membranes typically are heat-welded or torch-applied. Consumers should be cautioned that NRCA does not recommend torch-applying a modified bitumen membrane sheet directly to a wood deck. (NRCA, 2012)

We do not use or recommend APP modified bitumen products due to the inherent fire risk of the product.

Self-adhered products are a popular product for residential applications as they can be purchased with granule colors that closely match composition shingles, do not contain fumes associated with hot asphalt applications, and quicker to apply in smaller quantities.

Key benefits of Modified Bitumen products:

  • Durable and puncture resistant
  • A proven product
  • Will closely match shingle color and composition
  • Flexibility in application methods without performance implications
  • Long warranties
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