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Chapter 16 Roofing. First line of defense against the weather Precipitation (Rain, snow) Sun Thermal Transmission Subjected to extreme heat and cold Surface.

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Presentation on theme: "Chapter 16 Roofing. First line of defense against the weather Precipitation (Rain, snow) Sun Thermal Transmission Subjected to extreme heat and cold Surface."— Presentation transcript:

1 Chapter 16 Roofing

2 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 Metal Deck Welded to Structure 2 Rigid Insulation Mechanically Fastened

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 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

36 Parapet Parapet Flashing

37 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 – 12x36

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 Roofing Felt Asphalt Shingles - Packaged Laid from the Eave up

51 Ridge Treatment & Valley Flashing

52 Architectural Sheet Metal Roofing Materials – typically thin sheets of aluminum or galvanized steel Coatings – typically a polymeric available in various colors Seams – raised interlocking edge seams Fasteners – concealed or exposed fasteners with rubber washers

53 Lead Coated Copper

54 Roofing & the Building codes Classified based upon Flame Spread resistance Class A: effective against severe fie exposure Slate, concrete & clay tiles, asphalt shingles with glass felts, & most built-up and single ply Class B: effective against moderate fire exposure Many of the built-up & single ply, metal roofs, asphalt shingles based upon organic felts Class C: effective against light fire exposure Fire retardant wood shingles & shakes


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