Decra 300 High Performance Underlay
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Advantages
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Decra 300 High Performance Underlay is manufactured from a specially formulated polyethylene with a multifilament polypropylene reinforcement grid, providing exceptional strength and durability characteristics when compared to other leading underlays.
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Can be delivered at the same time as Decra tile delivery.
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Extremely durable.
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Superior tear resistance.
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Lightweight and strong.
Will not rot at gutter level.
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Decra Roof Systems in partnership with it’s sister companies within the Icopal group, the world’s largest producer of roofing felts, is now able to offer from stock high performance underlay ideally suited for use with the Decra Roof System.
Product Information:
Decra 300 High Performance Underlay, like all Decra Roof Systems products is light, extremely strong and easy to fix. It will not tear around nails and is comfortable to handle, even at low working temperatures. Designed to replace traditional BS 747 Type 1F bituminous based felts Decra 300 High Performance Underlay can confidently be expected to last the life of the roofing structure.
Decra 300 High Performance Underlay offers even greater strength and even higher performance than our base level TwoF underlay.
Decra 300 High Performance Underlay is suitable for use on all tiled roofs where insulation is provided at ceiling level and the roof is ventilated in accordance with BS 5250 Control of Condensation in Buildings.
Technical Data:
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Recommended horizontal laps for underlay
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| Pitch |
Minimum headlap |
Minimum
sidelap |
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Not fully
supported |
Fully
supported |
| 10° to 12° |
300mm |
200mm |
100 - 150mm |
| 12.5° to 14° |
225mm |
150mm |
100 - 150mm |
| 15° to 34° |
150mm |
100mm |
100 - 150mm |
| 35° + |
100mm |
75mm |
100 - 150mm |
NOTE 1. Any penetrations to the underlay should be suitably sealed to prevent water ingress.
NOTE 2. Roofing underlay laps to valleys should comply with recommendation’s of BS 5534; Part 1:1997 section 4.2.1.6
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Performance & Properties
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Nail Tear Resistance:
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106N (longitudinally) |
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(N per 50mm)
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124N (transversally) |
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Tensile Strength:
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289N (longitudinally) |
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(N per 50mm)
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294N (transversally) |
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Size and Coverage
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Roll Length:
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50m |
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Roll Width: |
1.0m |
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Thickness:
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0.30mm |
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Colour:
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Matt black top surface/grey underside |
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Cover per roll:
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45m² (approx. at 100mm lap)*
42.5m² (approx. at 150mm lap)*
38.7m² (approx. at 225mm lap)*
35m² (approx. at 300mm lap)*
*no allowance made in the above coverage’s for side laps and any wastage.
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Installation
Decra 300 High Performance Underlay must be installed with the matt black side uppermost.
For ease and accuracy of installation, overlap guidelines of 150mm from both edges are printed throughout the roll.
As per all types of underlay, at eaves the underlay should terminate in line with the front edge of the fascia board and to comply with the recommendations of DTLR Robust Detailing, BRE Defects Action Sheet No9 and BRE Good Repair Guides an appropriate Decra Eaves Guard must be installed underneath the breather membrane.