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J21 Mastic asphalt roofing/ insulation/ finishes

TYPES OF COATING/ PAVING

110 WARM DECK ROOF COATINGgenerally

• Substrate: Existing covering or new plywood deck.

- Preparation: site specific.

• Vapour control layer: site specific; refer to BS 5250 and BS 6229.

• Insulation: site specific; etermined by the contractor.

• Overlay: Two layers of building paper to BS 1521.

• Separating layer (loose laid): Reinforced bitumen sheathing felt.

- Laps (minimum): 50 mm.

• Coating: Mastic asphalt to BS 6925.

- Type: R988/ T25.

- Application: 20 mm nominal thickness in two coats.

• Surface protection: site specific but generally chippings.

• Accessories: site sepcifc but may include:

- Movement joints;

- Perimeter trims; and

- Ventilators.

120 INVERTED ROOF COATINGgenerally
• Substrate: Existing covering or concrete deck.
- Preparation: site specific.
• Separating layer (loose laid): Reinforced bitumen sheathing felt.
- Laps (minimum): 50 mm.
• Coating: Mastic asphalt to BS 6925.
- Type: R988/ T25.
- Application: 20 mm nominal thickness in two coats.
• Isolating layer (loose laid): Geotextile fabric recommended by insulation
manufacturer.
• Insulation: Extruded polystyrene board.
• Filter layer (loose laid): Geotextile fabric recommended by insulation manufacturer.
• Securement: Precast concrete paving slabs.
• Accessories: site specific but may include:
- Movement joints;
- Perimeter trims; and
- Ventilators.

RotF generic (intermediate) NBS 2014 6118-AEW-XX-XX-NBS-A-01