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Building Design and Construction Handbook - Merritt - Ventech!

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12.6 SECTION TWELVE<br />

ASPHALT<br />

ASPHALT<br />

GLASS<br />

FIBER<br />

FELT<br />

ASPHALT<br />

AGGREGATE<br />

FELT<br />

ASPHALT COATED<br />

BASE SHEET<br />

11 1 / 3�<br />

11 1 / 3�<br />

24 2 / 3�<br />

10�<br />

3� Lap<br />

BASE SHEET<br />

36�<br />

SECOND LAYER<br />

PREFORMED ROOF<br />

INSULATION BOARD<br />

24�<br />

ASPHALT<br />

BASE SHEET<br />

12�<br />

FIRST LAYER<br />

PREFORMED ROOF<br />

INSULATION BOARD<br />

ASPHALT<br />

SECOND LAYER<br />

SECOND LAYER<br />

FIGURE 12.1 Built-up roofing over two layers of preformed insulation<br />

board. Three plies of asphalt-impregnated glass-fiber felt,<br />

embedded in a continuous application of hot asphalt, overlay a<br />

base sheet adhered with asphalt to the insulation. Aggregate surfacing,<br />

about 3 ⁄8 in in diameter, is spread in the top flood coat of<br />

asphalt. (NRCA Roofing <strong>and</strong> Waterproofing Manual.)<br />

FIGURE 12.2 Protected-membrane roof with aggregate <strong>and</strong> insulation<br />

placed over, instead of under, the built-up membrane.

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