Polyethylene (HDPE/LDPE)
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Maintenance and Cleaning
| Types | Maintenance / Cleaning | Cleaning Frequency |
| Multi-laminate roof tile underlay of low and/ or high density polyethylene membranes and net reinforcement, incorporating anti-condensation fleece. Low to medium vapour resistance and medium to high vapour permeability (similar to minimum quoted in BS 5250 for traditional sarking felt of 50 MNs/g) | Inspection:
Annual inspection for underlay defect. |
None |
| Multi-laminate roof tile underlay of low density polyethylene (LDPE) reinforced with a net or ribs of high density polyethylene (HDPE). Non-perforated, with high water vapour resistance and low vapour permeability. | ||
| Multi-laminate roof tile underlay of low density polyethylene (LDPE) reinforced with a net or ribs of high density polyethylene (HDPE), or cross laminated wiht linear low density polyethylene (LDPE). High initial water vapour permeability which may be significantly reduced following shrinkage, blocking of perforations with dust etc | ||
| Polyethylene roof tile underlay with or without reinforcement and/ or perforations. Method of fabrication nor specified. Vapour resistance/ permeability not specified |