# Side Laps: Curved Roofs

Where a barrel curved roof is below the specified minimum roof pitch recommended for the profile, side laps should be sealed over the crest of the arch with lap tape or silicone sealant until the minimum pitch is reached. Avoid double lapping because condensation can become trapped in the lap, which can cause accelerated corrosion with all metal products.

If the width and height of the roof are known, this information can be used to obtain the radius of curvature and subsequently the sheet length and the length of seal required for any profile.

IMPORTANT NOTE: The seal length (s) is required on each side of the crest (b).

### Spring Curving Calculator

**Definitions**

The Code of Practice Online provides an interactive tool for these calculations. This tool is only available online at www.metalroofing.org.nz/cop/other-products/curved-roofs#spring-curving-calculator

**Enter width and height to calculate:**

**Full Calculation Details and Example**

**Formula**

**Example**

**w**= Width of roof

**h**= Height of roof

**r**the radius of curvature

**l**the sheet length

**y**

**x**

*the tangent of*angle

**A**

**A**

**c b**

**l**

p = Min Pitch for corrugate = 8°

N.B. This length of seal is required on each side of the crest.

### Curved Roof: Sealed Lap Pitch

Profile | Pitch |
---|---|

Corrugate | 8° |

Symmetrical Low Trapezoidal | 4° |

Asymmetrical Low Trapezoidal | 3° |

Secret-fix Tray | 3° |

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