SLE Cladding Limited

The 3" Iron corrugation (technical reference Sinusoidal) is used in the UK with all profiled corrugated metal sheets. This corrugation should not be confused with the Standard 3 corrugation that is only used with Fibre-cement and the now banned Asbestos Cement sheets and the matching PVC rooflights.

Each corrugation is 3" (76.2 mm) wide. The illustration above is known as a 10 x 3" corrugation, in that it has 10 effective coverwidth corrugations plus one extra for lap. All corrugated sheets of various widths have one more corrugation than their name implies. i.e. 8 x 3" corr. (9 no.) 10 x 3" corr. (11 no.) 12 x 3" corr (13 no.) usually to a maximum of 16 x 3" corr . (17 no.)

Note that the last half of the corrugation at each side of the sheet is cut short to 25mm when half a corrugation should be 38.1 mm. This is to prevent capillary action, where by the warmth inside a building draws moisture from the bottom of the corrugation up and over the corrugation and drips into the building. For all roofing application we generally advise the use of 2 no. side laps. In the case of curved corrugated sheets, 2no. laps is a must.

The above sheets is a 12 & one half x 3" corrugation with an extra half corrugation (turned up) on the right hand side. Note that the left hand edge points down whilst the right hand edge point up. Sheets with an extra half corrugation are not always available, but when they are they give a more secure seal on roofing applications and have added capillary protection. See the dotted corrugations representing the adjoining sheets.

Box Profile

The 32/1000 box profile above (technical reference Trapezoidal) is like all other box profiles simple in that it only has one lapping position. The short cut left hand profile laps OVER the full profile of the previous sheet, thus preventing the capillary action previously mentioned in corrugated sheets above.

END LAPS.

If there is more than one sheet down the length of the roof or roof lights are included. SLE Cladding Ltd recommend that a minimum lap of 6" either side of the centre line of the purlin (bearer) be used. The lower the pitch, the bigger the lap.

ROOF PITCHES of 10 Degrees and below.

In the cases of roof pitches of 10 degrees and below. All laps both side and end should be sealed by placing a bead of Butyl Sealant (Like putty on a roll) between the two lapping sheets. This prevents wind driven rain being driven up the slope under the top sheet and penetrating the building. This also applies to Corrosive Industrial Locations and Coastal Locations where corrosive salt spray can be driven between the sheets

For further information please contact SLE Cladding Ltd. Tel. 01948 666 321. Fax. 01948 66 55 32