Bitumen Sarking Felt
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Types and Durability
| Description
Reinforced Bitumen sheets |
Expected Lifespan
(Years) |
Adjustment Factors |
| Reinforced Bitumen Sheets classified as Type 1F to BS 747: 2000 or Type 1 to ASTM D 6221-00. Reinforcement of jute hessian | 35+ | Test certificate from approved local testing authority : +5 years |
| Reinforced Bitumen Sheets not manufactured to BS 747: 2000, Type 1F or Type 1 to ASTM D6221-00. | < 10 | None |
Note: All underlays should be fixed with large head felt nails of copper, aluminium alloy or galvanized steel and fixed in accordance with BS 5534 Part 1.
Insulating underlays should not cause obstruction in the batten and tile space
ASTM D1370-58: test for compatibility of bituminous materials
Some underlays may incorporate a layer of aluminium foil intended to increase the insulating effect of the underlay.