2 Rib profile sheet for wall cladding and moderate-span roofs

Where it is used

The 2 Rib is used mostly on the walls of factory sheds and warehouses, where its 200 mm pitch gives a closer rib pattern than the 250 mm of the 3 Rib. It is also used on roofs with moderate purlin spacing, and like the 3 Rib it is rated down to a 3° roof pitch. For a roof that people will walk on, the 3 Rib is usually the better choice, because its crest is domed to take foot traffic.

Specifications

Material

The sheet is rolled from galvalume coil with an AZ150 aluminium-zinc coating to AS 1397, in 550 MPa steel, finished with a 25 micron top coat of RMP or SMP paint. We buy the coil from JSW, Tata, AM/NS or POSCO, and the mill test certificate for the coil comes with the consignment.

On one railway station order we supplied 10,000 sq m of crimped 2 Rib sheet in 0.5 mm JSW colour coated steel. The sheet weighed 4.25 kg per sq m and carried a 10-year warranty from JSW Steel, supplied with a protective film. Warranty terms depend on the coil and the site, so we state them on the quote.

The thickness on our current specification letter is 0.5 mm TCT. That is about 0.45 mm of base metal. Other thicknesses from 0.3 to 0.7 mm TCT can be rolled on order (the approximate BMT for each is in our thickness guide), and we will give you the base metal thickness alongside the TCT so you can compare quotes on the same basis.

What the profile does

• The crests are 30 mm high and 25 mm wide, which gives the sheet its stiffness across the purlins.
• The flat pan between two crests carries two small stiffening ribs, which give the profile its name.
• Each sheet covers 1,000 mm once lapped, from a supply width of 1,060 mm, so you can work out sheet numbers straight from the building length.
• The side lap has an anti-capillary flute, a small channel that stops water being drawn sideways through the lap.
• The ends are formed with full return legs, so the edge sits properly on the next sheet.
• Sheets are cut to your lengths, up to 12 m, and sent by road.

Laying direction

Wherever practicable, the 2 Rib is laid so the exposed side-lap edge faces away from the prevailing wind and wind-driven rain, starting at the leeward end of the roof and working towards the wind. Rain is then pushed over the lap rather than into it. The 2 Rib has an anti-capillary side lap, so the approved MNF profile drawing and your project specification set the laying direction, and they take priority. On a roof, each side lap is stitched between the purlins with screws at 300 mm centres or closer. Our roof pitch guide explains how the side lap keeps water out.

Span and limits

Purlin spacing is set by our engineer against the wind and load on your site. Sheets longer than 12 m cannot go by road. On a longer roof we lap the sheets at the ends, by at least 200 mm, or 150 mm where the roof is steeper than 15°.

Colours

Standard colours from the coil suppliers' colour-coated range; RAL shades and special colours on order with a minimum quantity. Colours on screen differ from the coated sheet, so ask for a swatch before you decide.