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Chapter 16 Roofing

Chapter 16 Roofing. Roofing. First line of defense against the weather Precipitation (Rain, snow) Sun Thermal Transmission Subjected to extreme heat and cold Surface can have wide temperature swings. Roof Groups. Steep Roofs Low-Slope Roofs. Steep Roofs. Drain quickly

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Chapter 16 Roofing

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  1. Chapter 16 Roofing

  2. Roofing • First line of defense against the weather • Precipitation (Rain, snow) • Sun • Thermal Transmission • Subjected to extreme heat and cold • Surface can have wide temperature swings

  3. Roof Groups • Steep Roofs • Low-Slope Roofs

  4. Steep Roofs • Drain quickly • Less opportunity for gravity or wind to push/pull water through the roofing material • Facilitate the use of shingles • small, overlapping roofing units • Advantages: • Can be inexpensive, easy to handle & install, • Accommodate thermal expansion/contraction & structural movement • Vents water vapor easily • Visible - Aesthetics

  5. Low Slope Roofs • Low-Slope Roofs Advantages • Can cover a “large” horizontal surface (vs steep) • Simpler geometry, often less expensive • Roof can have other functions - patio, decks, parking, ... Disadvantages • Water Drains Slowly • Slight Structural Movements Tear the Membrane • Water Vapor Pressure Can Blister & Rupture the Membrane

  6. Low-Slope Roof Components • Structural Support - Deck • Thermal Insulation • Vapor Retarder • Roof Membrane • Roof Ballast • Drainage • Flashing

  7. Roof Deck • Materials (Plywood, OSB, Steel, Concrete) • Performance requirements • Support Roof Loading • Resist Uplift • Sloped for Drainage • Expansion & Contraction - Roof & Structure • Smooth, Clean Surface • Dry Prior to Membrane Placement

  8. Thermal Insulation • Resist Heat Transfer • Location / Placement • Below the Deck • Between the Deck & Membrane • Above the Membrane • Rigid Insulation Attachment (adhered or mechanically attached)

  9. ‘Rigid’ roof insulation being placed over metal decking (mechanically fastened to decking)

  10. Vapor Retarder • Purpose - Prevent transmission of Water Vapor • Location / Placement • Generally Below the Insulation • Material - hot mopped felts most common • Insulation Ventilation • Roof Vent

  11. Roof Membranes • Three Categories Built-up Roof (BUR) Membrane Single-Ply Roof Membrane Fluid Applied Roof Membrane

  12. Built-up Roof Membrane “Multiple plies of asphalt-impregnated felt bedded in bitumen” • Application: Felts laid in Hot Asphalt (or coal tar) Overlapping Layers Forms a “laminated” membrane typically 2-4 plies thick

  13. Asphalt Felts

  14. Felts being ‘Hot-Mopped’

  15. Kettle for heating the bitumen and pumping it to the roof

  16. Single-Ply Roof Membrane “Sheet materials that are applied to the roof in a single layer” • Attached to the Roof: Adhesives Ballast Weight Concealed fasteners

  17. Single Ply Materials • Thermoplastics • May be softened and joined by heat or solvent welding • Polyvinyl Chloride (PVC) – widely used, Polymer-modified bitumens, PVC alloys, etc. • Thermosetting • Can not be softened - must be joined by adhesives or pressure sensitive tapes • EPDM (the most widely used), Neoprene, CPE, etc.

  18. The following series of photos are from the roofing operations of a 47,000sf single story retail facility. • The roof system: • Uses rigid insulation over metal decking with a: • Thermoplastic Membrane where the • Sheets are mechanically fastened to the structure and the seams welded

  19. 2” Rigid Insulation Mechanically Fastened Metal Deck Welded to Structure

  20. Insulation Fastener

  21. Insulation Fastener - penetrates through the insulation to the metal deck

  22. Roof Membrane Rolls

  23. Lap Markings Fastener Locations

  24. Membrane being rolled out

  25. Rolled out & leading edge attached

  26. Membrane Mechanical Fastener (penetrates the insulation and anchors to the metal deck)

  27. Membrane Lap

  28. Welding Machine (welds the seams)

  29. Lap Welded

  30. Membrane Flashing @ Curbs

  31. Fluid-Applied Membranes “Membranes applied with a roller or spray gun and cure to form a rubbery membrane” • Uses “Complex shapes that are difficult to roof by conventional means” Examples: Domes and shells

  32. Ballast & Traffic Decks • Ballast Material • Stone aggregate • Precast concrete blocks or Pavers Purpose • Hold down membrane • Protect membrane from ultraviolet light • Protect membrane from physical wear • Traffic Decks – installed over membranes for walks, terraces, drives, etc.

  33. Roof Flashing - Roof Edge Edge Flashing

  34. Expansion Joint - Building Building/Roof Expansion Joint

  35. Area Divider Area Divider

  36. Parapet Parapet Flashing

  37. Roof Drain Roof Drain

  38. Roof Penetration Penetration - Vent

  39. Steep Roofs • Roofs with a pitch of 3:12 (25%) or greater • Three General Categories • Thatch • Shingles • Architectural sheet metal • Insulation & vapor retarder • Typically installed below the roof decking • Decking – typically plywood or OSB

  40. Shingles • “applied to the roof in small units and in overlapping layers with staggered vertical joints” • Materials • Wood (shingles & shakes) • Asphalt • Slates • Clay Tiles • Concrete Tiles

  41. Cedar Shakes (split rather than sawn) • Natural decay resistant wood • Moderately expensive • Fire Resistance low unless treated

  42. Asphalt Shingles • Die-cut from sheets of asphalt-impregnated • felt faced with mineral granules • Typical size – 12”x36”

  43. Different Asphalt Shingle Profiles & Colors

  44. Slate: • Fire-resistant • High initial cost, but long life

  45. Slate Roofing & Copper Flashing

  46. Slate w/ Predrilled Holes

  47. Clay Tiles

  48. Concrete Tile

  49. Asphalt Felt – typically adhered to the deck prior to the installation of the shingles

  50. Asphalt Shingles - Packaged Roofing Felt Laid from the Eave up

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