Single-Ply Roofing PDF

Single-ply Roofing  Why Single Ply?  Technology permits thinner, single-layer application—great flexibility, toughness  Weatherable-generally require no surfacing  Membrane produced under factory control  Light in weight, simpler tools required  Easier to make as a reflective p...

Single-ply Roofing  Why Single Ply?  Technology permits thinner, single-layer application—great flexibility, toughness  Weatherable-generally require no surfacing  Membrane produced under factory control  Light in weight, simpler tools required  Easier to make as a reflective product  May be safer, as no flame or hot bitumen needed  Single Ply Categories Weldable—Thermoplastics  Single Ply Categories Weldable—Thermoplastics Non-weldable—Elastomerics  Single Ply Systems  Weldable and Non-Weldable  Fully Adhered, Mechanically Attached or Loose-laid and Ballasted Full Adhesion Requires acceptable substrate (approved by manufacturer) Solvent-based contact adhesive Hot asphalt when “fleece” backer is used  Single Ply Systems Fully Adhered 2” Mechanically Plate Attached & Usually mechanical fasteners In lap area, with overlap Screw covering fastener In field of sheet, covered with batten cover Anchor May be disks or continuous bar & bars Screw  Single Ply Systems Loose-laid and Ballasted Ballasted application Secured only at perimeter and penetrations Rounded Stone may be acceptable direct to membrane “stone-mat” protector sheet when stone has “sharps” or when pavers are used #4 stone (1” dia) @ 10 psf for lower wind uplift loads #2 stone (2” dia) @ 20 psf for higher uplift (perimeters) Unsuitable for buildings >75ft tall  Single Ply Systems  Features  Factory Premanufactured  Widths—1 Meter (39in) to 50 ft.  Single Ply Systems Features  Field Joining  Adhesives or Tapes  More Common with “Cured Sheets”  Welding  Heat Fusion (Solvent Welding Rare Today)  Single Ply Attachment Options  Ballasted application  Secured only at perimeter and penetrations  Rounded Stone may be acceptable direct to membrane  “stone-mat” protector sheet when stone has “sharps” or when pavers are used  #4 stone (1” dia) @ 10 psf for lower wind uplift loads  #2 stone (2” dia) @ 20 psf for higher uplift (perimeters)  Unsuitable for buildings >75ft tall Single Ply Roofing Systems  Terminology of Polymers  Compounding of Materials  Manufacture of Roll Goods  Testing and Specifications Single Ply Terminology C Carbon Atom Forms 4 Bonds  Ethylene H H C C H H Double Bonds: One with the other Carbon-very strong-does not break or react The carbon—hydrogen bonds are also strong. The double bond is more reactive, can ‘open’ and join with other atoms to form new single bonds.  Polymerization H H H H C C C C H H H H Each Carbon still has four bonds: Double bonds have opened or ‘broken’, forming new carbon-carbon single bonds Ethylene has become ‘polyethylene’  Propylene H CH3 C C H H 3-Carbon atoms and one double bond  Close-packing or Lower density and “Crystallites” “Amorphic” If the ethylene chains are linear, they can fold back on themselves, forming higher density and higher melt point materials. However, if short branches are formed, the chains cannot pack so closely, and a lower density, less crystalline (amorphic) material results. Since polyethylene molecules only contain carbon and hydrogen atoms, they can only form weak attractions for other materials. Polyethylene is so inert it can be used in a chemistry laboratory to hold many chemicals.  H H+ C C H CL - But if we start with vinyl chloride instead of ethylene, the chlorine atom is very ‘electronegative’, causing a separation of charge.  PVC—polyvinyl chloride H H + C C C C H - Cl This allows solvent welding with Strong electrical polar solvents as well as attraction chain to bonding with adhesives. At high chain + temperatures, these polar H attractions weaken, allowing thermoforming and heat welding. R C R’ Plasticized PVC—polyvinyl chloride H H + C C C C H - Cl Plasticizers are used to weaken these pseudo-cross-links. Loss of plasticizer can result in both + H shrinkage due to loss of volume and embrittlement. R C R’ Dienes have 2 double bonds One can be use to form long molecules, while the other links with other atoms or molecules, forming a three dimensional network. Sulfur is frequently used as a vulcanizing agent. H H H H C C C C H H Once these sulfur cross-links form, they are as strong as carbon-carbon bonds and will not permit the chains to flow past one another when heated. The material has vulcanized and is thermoset. H H H H C C C C H H H Permanent Cross-link S Through Sulfur Atom R C R´  Neoprene Chloroprene Cl H H H C C C C H H Neoprene has 2 double bonds and a chlorine atom Neoprene (chloroprene) can be dissolved in polar solvents to form adhesives. It also can be vulcanized into a true elastomer. Sulfur Cross Links  Hypalon Chlorosulfonated Polyethylene (CSPE) H H H H H C C C C C C H H H Cl O S O Hypalon has both chlorine and Sulfonyl groups-can act as Cl thermoplastic or vulcanize Single Ply Roofing Systems  Terminology of Polymers  Compounding of Materials  Testing and Specifications  Thermoplastics Compounding  Polymers:  Polyethylene  Polyvinyl Chloride  TPO  KEE  Co- and ter-polymer blends (EVA)  Plasticizers and modifiers  Pigments—usually light colors  Fillers  UV Stabilizers, Fire Retardants, Processing Aids  Reinforcements and backings Reinforcements Add Strength Stabilize Distribute Stress Reinforcement for Single-Ply Woven Fabric (scrim) Scrim may wick water Selvedge has no fabric  Fully Adhered Single-Ply Bonding Adhesive Lap Adhesive, Tape or Welded Seam  Mechanically Fastened Single-Ply Overlap covers fasteners and forms seam Fasteners in seam area Membrane unadhered to substrate  Polymer-clad flashing and edge metal distributes stress and bridges substrate Heat Weld Caulk may be required to protect cut edges against wicking PVC-clad pipe sleeves  Slip-sheet to separate plasticized PVC from EPS or other incompatible substrate  Elastomers Polymers  EPDM  Butyl, Neoprene,  Polyepichlorohydrin  PIB  Reinforcing pigments-carbon black  Non-reinforcing pigments and fillers  Extending oils  Processing aids, fire retardants, UV stabilizers, anti-oxidants  May be reinforced or backed  Primer Primer and tape used as EPDM is non-weldable Tape Butyl Contact Adhesive May use neoprene bonding adhesive and butyl splicing adhesive or butyl splicing tape Single Ply Roofing