Roof Membranes:•Built-up roof membrane (BUR)

3 to 5 plies of felts with asphalt (bitumen) moppings betweenstone aggregate (3/8” and 400 lbs per sq) laid over a flood coat

•Modified bitumen roof membrane (MBR)2 to 3 plies of modified bitumen sheets with moppings between

•Single – ply membrane (SPR)one sheet of synthetic polymer (plastic)

Bitumen – • asphalt - waste product (residue) or distilled crude oil• coal tar – residue of distilled coal (literally “stinks”)

Roofing Asphalt – • ASTM specs 4 types (Type I, II, III, IV) Type III: most common• softening point temperature (SPT) 185° Type III• 25 lbs. per square for interply & 60 lbs per square for flood coat

Modified Bitumen Roof Membrane – polymers added• Styrene butadiene styrene (SBS) synthetic rubber (with mopped asphalt)• Attactic polypropylene (APP) greater UV resistance (open flame applied)

Felts (woven sheets)• organic – paper or wood fibers• inorganic – glass fibers (fiberglass)

asphalt-treated fiberglass felt (most common)

coal tar-treated fiberglass felt

SPR Single – ply membranes

1. Thermosetting polymer (unweldable plastic) does not soften with heat• Must use adhesives and or tape• EPDM (ethlene propylene diene monomer) a synthetic rubber

most common

2. Thermoplastic polymer (weldable)• Softens and rehardens with heat• Not as stretchable• PVC (polyvinyl cloride) and TPO (thermoplastic polyolefin) most common

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