ALM stock and supply
ancillary lead products...
Premium Underlays for lead roofing, cladding and weathering applications:
- Reduce drag arising from thermal movement of lead sheet over substrate.
- Assist in the protection of lead against condensation corrosion, or chemical attack from stone, concrete or timber.
- Protect lead from damage due to any uneven nature of substrate and provide support against downward pressure.
There are two categories of Premium Underlay:
- Conform to BS 1521 / AIF.
- Are suitable for smooth plywood decking (underside of decking must be ventilated).
- Can prevent chemical attack from smooth concrete, stone or oak surfaces.Must be fitted over whole substrate area.
- Are needle punched, non-woven, geotextile polyester materials in two unit weights – 200 and 220g.m-2
- Are suitable for more uneven surfaces, e.g. traditional timber boards.
- Do not rot or cause adhesion.
- Allow space for air flow between lead sheet and substrate.
ADVICE ON USE
- When using wood rolls, fit them over the underlay.
- Lay underlay in strips across the fall of the roof, lapping the upper layer over the lower and stapling the lengths in position (nails may damage underside of lead sheet).
- Create an upturn at abutments. Avoid draping underlays downwards at edges, as moisture may be drawn up by wick effect.
- Take care when lead welding etc, as flames will ignite paper and melt textile.
- Ensure that the lead sheet is laid on dry substrate and underlay.
Standard AIF – 1000mm x 25m
Polybit Moistop – 1000mm x 25m
Geotextiles: Geotec – 1000mm x 25m
HEALTH & SAFETY ADVICE
- Premium Underlays may be handled without special precautions.
- When working with lead, follow standard health and safety procedures as laid out in Control of Lead at Work Regulations 2002. Always wash hands well before eating, drinking or smoking.
- Remove lead residues from skin after working with lead metal by washing with Premium Metwash – Soap and Bodywash.
Standard AIF: Waterproof, reinforced building paper for use as underlay, separation, curling layer and vapour check membrane.
Polybit Moistop: Polyethylene coated, building paper for use as a damp proof membrane.
Unit weight: 220g.m-2
Tensile strength: 16.5 kN.m-2
Pore size: 0.09mm
Puncture resistance: 2500 N
PRODUCT INFOMATION SHEET
Water permeability: 220 I.m-2 .s-1
Flame test: Satisfactory according to BS479:Part 12:1991