Membrane Options

Comparison Asphalt Built Up Roofing SBS Modified Bitumen TPO/PVC EPDM Inverted or Protected membrane
# plies 4 or 5 2 1 1 2, 4 or 5
Overall membrane thickness 13 mm or more 7 mm 1.5 mm 1.15 mm 7 mm
Weight of roof membrane and ballast (per square foot) 7 lbs 1.75 lbs .25 lbs .37 lbs without ballast or 11.37 lbs with ballast 12.7 lbs
Weight of roof membrane and ballast (per square foot) 34.17 kg 8.54 kg 1.22 kg 1.81 kg without ballast or 55.51 kg with ballast 62 kg
Ballasted system Yes No No Possible Yes
Benefit – membrane UV resistant Yes, when covered with asphalt and ballast Yes, with granular cap sheet Yes, some concerns exist Yes Yes
Benefit – long life expectancy with proper maintenance (1 highest – 5 lowest) 2 2 4 4 1
Benefit – forgiving assembly due to higher number of membrane plies and thicker overall membrane (1 highest – 5 lowest) 2 2 4 5 1
Benefit – allows for cold weather application Yes No Yes No Application of ballast is difficult
Benefit – all plies are solidly attached Yes Yes No, unless fully adhered No, unless fully adhered Yes
Benefit – allows for inexpensive overlay No Yes Yes Yes, harder with ballast No
Concern due to the use of open flame Yes Yes, possible workaround No No Yes, possible workaround
Concern due to odour Yes Depends on system selection No No Depends on system selection