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Title: Section 1516  •  Size: 7913

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SECTION 1516 - BUILT-UP ROOFS

1516.1 General. Built-up roof covering shall be completely removed before applying the new roof covering. New roofing conforming to Section 1503 shall be applied except that when the new roof is to be applied directly to a nailable deck which has residual bitumen adhering to it, a rosin-sized or other dry sheet shall be installed prior to the installation of the new roof system.

EXCEPTION: The building official may allow existing roof coverings to remain when inspection or other evidence reveals all of the following:

1. That the roof structure is sufficient to sustain the weight of the additional dead load of the roof covering.

2. There is not more than one existing roof covering on the structure.

3. The existing roof covering is securely attached to the deck.

4. The roof deck is structurally sound.

5. The existing insulation is not water soaked.

1516.2 Preparation of Roof and Application of New Covering.

1516.2.1 General. When reroofing without removal of existing roof coverings is permitted by the building official and when the conditions specified in the exceptions to Section 1516.1 above have been met, the reroofing shall be accomplished in accordance with this section.

1516.2.2 Over gravel-surfaced roof coverings. Over gravel-surfaced roof coverings, the roof shall be cleaned of all loose gravel and debris. All blisters, buckles and other irregularities shall be cut and made smooth and secure. Minimum 3/8-inch (9.5 mm) insulation board shall be nailed or securely cemented to the existing roofing with hot bitumen over which a new roof complying with Section 1503 shall be installed. When insulation board is to be attached with hot bitumen, the existing surface shall be primed.

Alternatively, on nailable decks only, all existing gravel shall be spudded off to provide a smooth surface. All blisters, buckles and other irregularities shall be cut and made smooth and secure. A rosin-sized or other dry sheet shall be installed and a base sheet as defined in the code shall be mechanically fastened in place. New roofing conforming to Section 1503 shall be applied.

1516.2.3 Over smooth or cap-sheet surface. Over smooth or cap-sheet surfaced roof coverings, all blisters, buckles and other irregularities shall be cut and made smooth and secure. In the case of nonnailable decks, a base sheet shall be spot cemented to the existing roofing. New roofing conforming to Section 1503 shall be applied.

In the case of nailable decks, a base sheet shall be nailed in place. In those cases where residual materials may cause the new base sheet to adhere to the old roof, a rosin-sized dry or other sheet shall be installed under the base sheet. New roofing conforming to Section 1503 shall be applied.

1516.3 Construction Details.

1516.3.1 Flashings and edgings. Vent flashings, metal edgings, drain outlets, metal counterflashing and collars shall be removed and cleaned. Rusted metal shall be replaced. Metal shall be primed with cutback primer prior to installation. Collars and flanges shall be flashed per the roofing manufacturer's instructions.

1516.3.2 Intersecting walls. All concrete and masonry walls shall be completely cleaned and primed to receive new flashing. All vertical walls, other than concrete or masonry, shall have the surface finish material removed to a height of approximately 6 inches (153 mm) above the deck new roof surface to receive new roofing and flashing. All rotted wood shall be replaced with new materials. Surface finish material shall be replaced.

1516.3.3 Parapets. Parapets of area separation walls shall have noncombustible faces, including counterflashing and coping materials.

EXCEPTION: Combustible roofing may extend 7 inches (178 mm) above the roof surface.

1516.3.4 Cant strips. Where space permits, cant strips shall be installed at all angles. All angles shall be flashed with at least two more layers than in the new roof with an exposed finish layer of inorganic felt or mineral surfaced cap sheet.

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