McArthur Group Ltd

Roofing Products Roofing Products

All over Britain, the McArthur Group has an important role to play in keeping out the elements. Factories, garages, superstores, sports halls - a mulititude of modern buildings use the latest roofing materials as supplied by McArthur

Our huge range of specialist roofing, cladding and roof lights includes everything from corrugated iron for farm buildings and PVC sheets for use around the home, to coated steel cladding used in factories and superstores.

Dalpro®

The low resistance vapur permeable air barrier roofing underlay

Dalpro® can be used in both ventilated and non-ventilated cold & warm pitched roof systems for tiles and slates. In mainland UK and Northern Ireland the underlay should be iustalled in accordance with British Board of Agrement Certificate No. 07/4442.

Non Ventilated Cold roofs

In non ventilated cold roof constructions tiling battens at least 25mm thick must be used to ensure an adequate airspace between the roof covering and Dalpro® to sllow water vapour to disperse above the underlay.
In non ventilated cold roofs it is essential to maintain a convection tight ceiling. As such all penetrations of the ceiling must be sealed and loft hatches made convenction tight by, for example using a compressible draught seal.

Warm roofs

BS5250:2002 specifies that if a vapour permeable underlay is used in a warm roof there must be an adequate flow of air through the batten space. If the underlay is unsupported with drapes, no counterbattens are needed, however if the underlay is fully supported on the insulation counterbattens must be provided.

General Installation Information

Dalpro® should be fixed to the rafters or boarded sarking with the coloured side uppermost. tiling battens, and where appropriate counter battens, should be fixed over the membrane ensuring, where the membrane is unsupported, that there is sufficient drape to allow moisture and air movement. where the membrane is required to be draped this should be more than 6mm and less than 25mm. Dalrp® is unrolled horizontally across the roof starting at the eaves. Subsequent rows of membrane should be lapped over the underlying row to shed water out and down the slope. Suffcient
vertical overlap should also be allowed.

Minimum Overlaps

Roof Pitch (o)	Horizontal/Lap (mm)		Vertical Lap Limit (mm)
	Partially Supported	Fully Supported
12.5 to 14	225	150	100
15 to 34	150	100	100
35+	100	75	100

Note: For Republic of Ireland a horizontal overlap of 225mm should be maintained for partially supported roofs up to a roof pitch of 22.5°. All other values in the table above are valid for ROI.

Eaves and roof edges - Dalpro® should be unrolled scross the roof and draped a minimum of 150mm onto the proprietary eaves carrier.
Ridges - In duo-pitched roofs Dalpro® from one elevation should overlap the other by at least 150mm. Dalpro® should be sealed around penetrations through the roof at the ridge to accomodate high level void ventilation. With mono-putched roofs Dalpro® should be extended over the mono ride at least 100mm.
Verges - At verges Dalpro® should be lapped over the outer walling by at least 50mm. Where the verge has a constructed overhang Dalpro® should be fixed to the outer rafters.
Abutments - Dalpro® should be returned up the abutment by at least 75mm below either a proprietary plastics or lead flashing
Hips and Valleys - Should be covered with a seperate 600mm wide strip of Dalpro ®