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Water Mgmt : Flashing
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Water Mgmt : Flashing

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  • 1. Water Management F L A S H I N G p r e s e n t a t i o n
  • 2. Presentation Outline
    • Water Management System (WMS)
      • Nature of Water
      • WMS Components
    • Exterior Shell Performance
      • Roofing
      • Walls
    • WMS Focus: Flashing
      • Flashing Types
      • Roof Flashing
      • Wall Flashing
    • Conclusions
  • 3. Water Management SYSTEM
    • Water Issue?
      • Knee jerk reaction: Blame the FLASHING
    • While researching FLASHING, other WMS components always mentioned:
      • Air and Vapor Barriers
      • Heat Barrier
      • Water Barrier
  • 4. Water Management SYSTEM
    • WMS Presentations
      • Part I: Flashing (PM Workshop)
      • Part II: Water Barriers (PM Workshop)
      • Part III: Air/Vapor/Heat Barriers (PM Workshop)
      • Part IV: WMS Detailing (Studio Workshops)
        • Masonry Walls
        • Veneer Systems
        • Wood Construction
  • 5. WMS: Nature of Water
    • (3) Physical States of H20
      • Liquid (water)
      • Vapor (gas)
      • Solid (ice)
    • Sources of Moisture
      • Liquid/Solid:
        • Precipitation (Rain, Sleet, Snow)
        • Condensation
      • Vapor:
        • Artificial Humidification
        • Relative Humidity
  • 6. WMS: Nature of Water
    • Driving Forces for Rainwater Penetrations
      • Gravity
        • Draw water down thru openings into assembly
      • Surface Tension
      • Capillary Suction
        • Sucks water thru cracks/pores
      • Momentum
        • Pass thru openings in exterior cladding
      • Air Pressure Differential
        • Push/pull water thru cracks/pores
  • 7. WMS: Components
    • Air and Vapor Barriers
    • Heat Barrier
    • Flashing
    • Water Barrier
  • 8. WMS: Air & Vapor Barriers (AVB)
    • Most materials are effective
      • AIR Barriers
        • Needs to be continuous
          • Intersections between wall/roof, floors, foundation
          • Interface of wall assembly & door/window/curtain walls
          • Penetrations thru AB
          • Joints/seams between sheets/boards of AB
    • Few materials are complete
      • VAPOR Barriers
        • Place on warm side (winter) of Heat Barrier (insulation)
          • Vapor arrested before it reaches colder surfaces
          • Moist, warm air moves TO cooler, dryer air
    • More accurate description: Vapor Retarders
  • 9. WMS: Components
    • Air and Vapor Barriers
    • Heat Barrier
    • Flashing
    • Water Barrier
  • 10. WMS: Heat Barrier (Insulation)
    • Heat Transfer
      • Decrease as the wall’s thermal resistance increases
    • R-Value: thermal resistance
    • Common pitfalls
      • Inappropriate location
      • Discontinuity
        • Thermal bridging
      • Dewpoint
        • Condensation & staining issues
  • 11. WMS: Components
    • Air and Vapor Barriers
    • Heat Barrier
    • Flashing
    • Water Barrier
  • 12. WMS: Flashing
    • Main Causes of Moisture Intrusions
      • Interface details
        • Bldg envelope penetrations
          • Decks
          • Windows
          • Doors
      • Flashing
        • Did not exist OR were not integrated with the rest of the WMS
  • 13. WMS: Components
    • Air and Vapor Barriers
    • Heat Barrier
    • Flashing
    • Water Barrier
  • 14. WMS: Water Barrier (WB)
    • Forms vertical surface behind cladding
      • Allows water to drain out of the wall system
    • Exterior cladding protects WB
      • Weather
      • Ultraviolet (UV) Radiation
    • Lets wall components dry safety
      • Allows internal vapor to escape out
    • Most important deterrent against liquid water penetrating INTO the bldg enclosure
      • Acts as a barricade - Continuous & shingled
  • 15. WMS: Components
    • Map out the PASSAGE of water
      • Drainage Space
        • Allows free drainage of water
      • Drainage Plane
        • Water Barrier (WRB)
          • Overlapping
          • Integrating w/flashing
      • Flashings
      • Weep Holes
        • Located DIRECTLY above flashing
  • 16. Exterior Shell Performance
    • Continual expansion & contraction
      • Moisture content + Thermal
    • Corrosion: Metals
      • Electrolytic action causes a current to flow
      • Water is the electrolyte to complete the circuit
      • Electronic potential:
        • Metal A + Metal B
        • Metal A + Water + Salt
      • Example: Storing planes in the desert
    • Decay: Wood
      • Food (wood) + water + air+ temperature
      • Example: Submerged trees in water
    • Efflorescence: Masonry
      • Migrating water dissolves salts inside material and deposits them on it’s surface
    • Leaching: Concrete & Mortar
      • Leaching out the calcium from the calcium chloride
  • 17. Exterior Shell Performance
    • (3) Types of Exterior Wall Design
      • Face-Sealed Barriers
        • EIFS (non-drainable)
        • Curtain Walls (face-sealed)
      • Concealed Barrier Walls
        • Stucco system (drainable)
        • EIFS (drainable)
      • Drain Cavity or Rain Screen
        • Brick-veneer cavity walls
        • Furred-out clapboard walls
        • EIFS (drainable w/membrane)
  • 18. Exterior Shell Performance
    • Face-Sealed Barriers
      • Every seam/crack is sealed
      • Requires detailed workmanship
      • Requires continuous maintenance
      • Most vulnerable to rain infiltration
      • Effective in areas with:
        • Low wind and low rain exposure
  • 19. Exterior Shell Performance
    • Concealed Barrier Walls
      • Relies on multiple layers for rain penetration
      • Provides (2) lines of defense
      • Drainage plane in the wall assembly
        • Usually a water-resistive barrier membrane
      • Requires continuous maintenance
      • Effective in areas with:
        • Moderate wind and moderate rain exposure
  • 20. Exterior Shell Performance
    • Drain Cavity or Rain Screen
      • Relies on (2) layers + drained cavity for rain penetration
      • Provides (2) lines of defense
      • Drainage plane in the wall assembly
        • Usually a water-resistive barrier membrane
      • Additional features:
        • Capillary break between porous materials
        • Freer drainage
        • Venting limits relative humidity (RH) outboard of sheathing
      • Effective in areas with:
        • High wind and high rain exposure
  • 21. Exterior Shell Performance
    • Drainage Wall System
  • 22. Exterior Shell Performance
    • Enclosure Performance depends on:
      • Proper Sequencing
        • Exposure Duration
      • Detailing
        • Spec vs. Drawings
        • Field vs. Pre-fab
      • Construction Material’s Recovery
        • Ability to get wet and then dry out
        • Not deteriorate or contaminate (microbes)
  • 23. Flashing - Types
    • Sheet Metals
      • Stainless Steel
      • Galvanized Steel
      • Copper (Cold Rolled)
      • Copper (Lead-Coated)
      • Aluminum
    • Composite Materials
      • Copper Laminates
      • Aluminum Laminates
      • Lead Laminates
    • Fabrics
      • PVC
      • Rubberized Asphalt
      • EPDM
  • 24. Flashing – Sheet Metals
    • Advantages
      • Extend beyond face of wall
        • Forms drip edge – conducts water out
      • May be soldered
        • Mastics or sealants need not be solely relied upon
      • Stiffness allows for proper geometries
      • Can be exposed to weather
      • Suitable substrate for construction sealants
    • Disadvantages
      • More expensive than membrane flashing
      • Aluminum corrodes in an alkaline environment
        • Masonry Mortar
        • Concrete
  • 25. Flashing – Composite/Fabrics
    • Advantages
      • Less expensive than metal flashing
      • Self-sealing properties
    • Disadvantages
      • Must be continuously supported
        • To avoid creating water pockets
        • To provide a solid substance for proper seaming
      • Relies on field installer
        • Bed & seal membrane (transverse seams)
        • Unsuitable substrate for common construction sealants
      • Exposure issues: degradation due to sunlight
        • Must terminate at/inboard of wall face
        • This encourages water bypass at front edge of membrane
  • 26. Flashing – Considerations
    • Main Criterion: Expected Life
      • Flashing MUST last as long as life of building
    • Cost
      • Material Cost
      • Installation Cost
      • Maintenance Cost
    • Installation
      • Ease of Installation
      • Ease to Join
      • Ease of Fabrication
    • Performance
      • Compatibility with materials
      • Resistance to punctures/tears
      • Resistance to UV
      • Resistance to Corrosion
    Flashing with Metal Drip Edge
  • 27. Flashing – Comparison
  • 28. WMS: Flashing – Where?
    • Where Water Barriers (WB) terminate
    • B30 Roofing
      • B3010 Roof Coverings
      • B3020 Roof Openings
    • B20 Exterior Closure
      • B2010 Exterior Walls
        • Top of exterior walls & parapets
        • Base of exterior walls
        • Penetrations through the wall assembly
        • Shelf angles (cavity walls)
    • B2020 Exterior Windows / B2030 Exterior Doors
        • Perimeters of openings: Head, Sill, & Jamb
    • A10 Foundations (exposed)
  • 29. Flashing: Roofing – Where?
    • Terminations
      • Expansion joints
    • Junctions
      • Examples:
        • Penthouses
        • Skylights
        • Chimneys
        • Equipment Housing
        • Parapets
      • Thru-wall needs to lead water out of the wall
      • Parapets: exposed on exterior, interior and top
  • 30. Flashing: Roofing – Where?
    • Penetrations
      • Examples: pipes, ducts
      • Group many into a single curb
      • Differential movement
      • If connected- flashing flexible to move with it
      • Minimize quantity
      • Small pipes/ducts
        • Separate support for base flashing not used
        • Sleeves (metal or plastic flanged): require frequent maintenance
        • Counterflashing + cover
    • Joints
  • 31. Flashing: Roofing
    • Prevents water from penetrating exterior surface
      • Intercepts water at parapets, walls, penetrations
      • Diverts it
      • Leads it out to the membrane
      • Flows out to the roof drains
    • Think of roof membrane as one large flashing designed to hold water until drainage system takes over
    • Detail Components
      • Base flashing
      • Counter-flashing
      • Cap flashing
    Concrete Roof Slab Dtl
  • 32. Base Flashing (Roofing)
    • Extension of the roof membrane or a different material bonded to form a waterproof joint
    • Extends upward along vertical surface
    • Diverts water onto the membrane
    • Pass over top of parapet or cant
      • Minimize of water leaking behind it
      • Liquid-applied: not suitable
        • Cannot be carried over a parapet/roof-wall joint
      • Reach higher than water could be “stored”
  • 33. Counter-Flashing (Roof)
    • Description
      • Carries water onto base flashing/membrane
      • Covers vertical face of base flashing
      • Secured to the parapet or wall cladding
      • Not connected to base flashing
      • Provides physical and UV protection for base flashing
      • Not expected to watertight
    • May not be required with some roofing types:
      • Modified bitumen
      • Single-ply membranes
    • If not required, don’t include it
      • Covers up defects & hinders maintenance
    • Details requiring reglets should be avoided
  • 34. Cap Flashing (Roof)
    • Horizontal coverings for parapets & expansion joints
    • Sloped toward roof
    • Secured to allow differential movement
    • Not expected to watertight
    • Provides physical and UV protection for base flashing
    • Only aesthetic with some roofing types:
      • Modified asphalt
      • Single-ply membranes
  • 35. Cap Flashing (Roof)
  • 36. Roof Flashing - Summary
    • Compatibility between base flashing & the membrane
    • Ease of right angle turns in built-up roofs
      • Cants prevents puncturing of flashing membranes
    • Differential movement
      • Counterflashing and wall/parapet it is secured
      • Roof deck and wall/parapet
    • Failure of reglet seals
      • Caulk not maintained
      • Counterflashing moves
  • 37. Flashing: Walls – Where?
    • Critical Locations
      • Top of the Wall
        • Parapet
      • Openings
        • Head
        • Sill
        • Jamb
      • Through Wall
        • Shelf Angles
      • Base of Wall
        • Where wall rests on foundation
  • 38. Flashing: Openings
  • 39. Flashing: Head Window Head Detail and Cavity Seal
  • 40. Flashing: Head
  • 41. Flashing: Window Lintel
  • 42. Flashing Details - Sills
  • 43. Flashing Details - Sills
  • 44. Flashing: Window Sill Commercial aluminum window in metal stud with exterior gypsum board sheathing
  • 45. Flashing: Window Sill
  • 46. Flashing: Interruptions        Lipped Brick Detail
  • 47. Flashing: Base of Wall
  • 48. Flashing: Base of Wall Base flashing with concrete wall backup and masonry veneer
  • 49. Flashing: Base of Wall
  • 50. Flashing: Base of Wall
  • 51. Flashing: Coordination
  • 52. Flashing: Critical Details
    • Critical Details
      • Inner & Outer Corners
        • Field Fabricated
        • Preformed Corners
      • Lapping
        • Horizontal – Flashing
        • Vertical – Water Barrier
      • Terminations
        • Drip Edges
        • End Dams
          • 6”-8” beyond jamb
      • Keep Air Space (AS) clean
        • Veneer (wood frame): 1”
        • Veneer (steel frame): 2”
        • Cavity (w/rigid insul): 1”
        • Cavity (w/no insul): 2”
        • Cavity (w/rigid insul & drainage panel): 0- 3/8”
  • 53. Conclusion
    • Water: BAD - Flashing: GOOD
    • Flashing Rules of Thumb
      • Continuity
      • Extend past face of wall
        • Divert water OUT
      • Seal top of flashing (water barrier)
      • Protect flashing from punctures
    • Managing water with a SYSTEM
      • Ounce of prevention = Pound of cure
      • Initial cost < Future Repair / Liability
  • 54. Conclusion
    • Q uestions???
    • C omments???
    • C oncerns???
    • S uggestions???
  • 55. Water Management F L A S H I N G T H A N K Y O U
  • 56. Detailing – Detail on CD’s
  • 57. Detailing – Detail on CD’s
  • 58. Detailing – Sequencing A
  • 59. Detailing – Sequencing B
  • 60. Detailing – Sequencing C
  • 61. Detailing – Sequencing D
  • 62. Detailing – Sequencing E
  • 63. Detailing – Sequencing F
  • 64. Detailing – Sequencing G
  • 65. Detailing – Sequencing H
  • 66. Detailing – Sequencing I