Manufactured by Boral Roofing, Boral® Ply 40 is an SBS modified fiberglass reinforced underlayment/base sheet for tile, shingle or shake roofing. Easily installed and ideal for use with metal roofing systems, Boral Ply 40’s modified asphalt minimizes the wrinkling and buckling that is commonly associated with non-modified membranes. An all-season solution, Boral® Ply 40 offers durability and better protection than felt at a low cost.  

The recently improved underlayment now offers an uncovered exposure time, without any degradation, of six months (an improvement from its original three month uncovered exposure time).