Flat Roofs

Here is an attempt clearly identify the current options available for flat roofing systems.  First off, remember the basic intention that flat roofs need to drain water by having a slight slope.  Here are the types as found on the Wikipedia - Flat roof page.  I've tried to both summarize this list and add in other information for architectural consideration.   Please comment if you can provide any correction or additional information.

Coal-Tar Pitch Built Up Roof

• Byproduct of coal industry
• Heated coal tar between layers of saturated felt
• Can soften in warm temperatures and 'heal' itself
• Always ballasted with gravel on top
• Proven longevity
• Fumes are hazardous
• Melted in kettle on site
• Slope of 1/4" per foot or less.

Asphalt Built Up Roof

• Currently the most common flat roof
• Multiple layers of reinforcing plies and asphalt for redundancy
• Gravel surfacing material is common
• Cracking and UV degradation are concerns
• Byproduct of oil industry
• Melted in kettle on site
• Can later repair and recoat with compatible product
• 4 Types
  • Type I: used on dead level, closet to coal tar
  • Type II: up to 1/4" per foot
  • Type III: up to 2" per foot
  • Type IV: 'special steep'

Turbo Seal

• Self healing gel like membrane that never cures
• Rubber (mostly used tires) infused with adhesives
• Applied to existing asphalt roof. Then cap with sheet membrane

CSPE - Chlorosulfonated Polyethylene

• Synthetic rubber roof
• Seams are 'welded'

EPDM - Ethylene Propylene Diene Monomer

• Synthetic rubber roof
• Single ply
• Simple to apply
• When air conditioned space beneath, moisture gain can be a problem
• Does not like to adhere to itself.  Seams can be a problem.
• Low cost membrane
• Three methods of installation:
  • Ballasts on top of membrane
  • Mechanically attached
  • Fully adhered (expensive, but best performance)

Cold applied liquid membranes

• Increasing in popularity
• No flames or heat needed
• Seems to be excellent at covering intricate changes in plane
• Can anyone report on long term performance and maintenance of these products?
• Steps I observed in a recent maufacturer presentation
  • Paint on layer of polyurethane
  • Roll out a sheet of fiberglass reinforcement
  • Upon reacting with the polyurethane, fibers 'relax' and become embedded.
  • Paint on a second layer of polyurethane

PVC - Polyvinyl Choride

• Single ply
• Flexible
• Additives improve UV degradation
• More information on Roofingcontractor

TPO - Thermoplastic Polyolefin

• Single ply
• Seams can be heat welded
• Resistant to heat and UV degradation
• More information at National Research Council Canada

Comments

[castors]

A flat roof is a type of covering of a building. In contrast to the sloped form of a roof, a flat roof is horizontal or nearly horizontal. Materials that cover flat roofs typically allow the water to run off freely from a very slight inclination.