ARCH 432_Cpater 16 - ARCH 432 Chapter 16 the Roof 1 First...

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ARCH 432 Chapter 16 – the Roof 1. First line of defense a. Rain, snow, sun a.i. Solar radiation a.ii. Hot to cold a.iii. Freeze/thaw 2. Jorn Utzons – Sydney Opera House 3. Baskavard Church 4. Two groups of roofs a. Steep slope b. Low slope c. No flat roofs – all roofs have a slope 5. Steep Roofs – drain quickly a. Shingles or tiles appropriate b. Many inexpensive c. Easy to handle and install d. Repair is easy e. Thermal expansion / contraction minimized f. Water vapor vents easily 6. Low slope a. Advantages a.i. Can cover large horizontal surfaces a.ii. Simpler geometry / less expensive a.iii. Can be decks, balconies, or even green surfaces b. Issues b.i. Water drains slowly b.ii. Trapped water is possible b.iii. Structural movement can damage b.iv. Water vapor can damage 7. Low slope a. Slopes less than 3:12 (25%) – 3’ forward 1’ down b. Major Components b.i. Roof Deck – structural surface b.ii. Thermal insulation – slows passage of heat b.iii. Vapor retarder – prevents moisture accumulation b.iv. Membrane – prevents water penetration b.v. Ballasting – prevents uplift, protects Drainage components b.vii. Flashings 8. Roof decks a. Must be adequately stiff a.i. Loads and uplifts b. Minimum slope: ¼” / foot (1:50) 9. Slope – pg. 600 a. Sloped beams
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b. Tapered concrete decking on level structure c. Tapered rigid insulation boards d. Insufficient slope: puddling or ponding 10. What would cause a low slope roof to fail? – test questions 11. Insufficient slope a. Puddling a.i. Premature deterioration of membrane b. POnding b.i. Water accumulation due to structural deflection b.ii. Possible structural collapse 12. Roof deck a. Large areas require expansion / contraction considerations – pg. 618 a.i. Deck can have movement joints to accommodate need of the deck and the membrane OR a.ii. Membrane can have area dividers, which allows movements of membrane only 13. Deck must be smooth – pg. 600
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ARCH 432_Cpater 16 - ARCH 432 Chapter 16 the Roof 1 First...

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