- 19 Sep 2023
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# Roofing Formulas

- Updated on 19 Sep 2023
- 2 Minutes to read

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- PDF

Before reading this article, ensure you have read Measurement - Parts & Labour and Using Formula within Groundplan articles to aid in understanding the following Formula examples.

- If there is more than one roof pitch required on the Project, each pitch must be a separate Measurement with the correct Formula, Parts and/or Labour applied.
- The Roof Pitch Chart will assist with common roof pitches.
- Find the secant of a slope using a scientific calculator.

📝 The Formula values provided in this article are for example purposes only.

Term | Explained |
---|---|

`count` | total counts |

`len` | total metres measured |

`area` | total square metres measured |

`count, len or area / x` | total count/length/area divided by an `amount` |

`count, len or area * x` | total count/length/area multiplied by an `amount` |

`ceil(x)` | rounding up a decimal value to the next whole number |

## Roofing

Example Parts for Roof area (26° pitch) using an Area Measurement:

Part | Explanation | Formula | UMO |
---|---|---|---|

Roof area (26° pitch) | The area measured multiplied by the `roof pitch of 1.1126` | `area*1.1126` | m2 |

Roofing screws (8 per m2) | How many screws are required for the area measured multiplied by and allowing for `the 26° pitch` divided by `8 per m2` `250 screws in a box` | `ceil(area*1.1126*8/250)` | boxes |

Insulation / wool / sarking (18m2 coverage) | How many rolls are required for the area measured multiplied by divided by `the roof pitch` `based on 18m2 coverage` | `ceil(area*1.1126/18)` | rolls |

## Guttering

Example Parts for 125mm half round guttering Length Measurement:

Part | Explanation | Formula | UMO |
---|---|---|---|

125mm half round guttering (7m lengths) | How many are required of 125mm half round guttering`7 metre lengths` | `ceil(len/7)` | lengths |

125mm gutter brackets | How many gutter brackets are required for the divided by `length measured` intervals`1.5 metres` | `ceil(len/1.5)` | brackets |

## Downpipe

Example Parts for a downpipe Count Measurement:

Part | Explanation | Formula | UMO |
---|---|---|---|

100mm DVW pipe (6m) | How many are required to complete downpipes when 3 metres `6m lengths` is needed for each downpipe`1/2 length (3m)` | `count*0.5` | lengths |

100mm PVC 90° bend | How many are required when `90° bends` are needed for each downpipe`3` | `count*3` | each |

100mm saddle clip | How many are required when `saddle clips` are needed for each downpipe`3` | `count*3` | each |

100mm classic expansion outlet | How many are required for each downpipe`expansion outles` | `count` | each |

Downpipe nozzle | How many are required for each downpipe`nozzles` | `count` | each |

(optional) 100mm junction (for 80%) | How many junctions required for needed`80% of the downpipes` | `ceil(count*0.80)` | each |

For Formula assistance, please reach out to Support. Go to: **Help > Send us a Message.**

Download a PDF copy of Using Formulas within Groundplan here.

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