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Roofing Formulas
- 03 Jan 2024
- 2 Minutes to read
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Roofing Formulas
- Updated on 03 Jan 2024
- 2 Minutes to read
- Print
- DarkLight
- PDF
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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.
Please note:
- 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 | area*1.113 | m2 |
| Roofing screws (8 per m2) | How many screws are required for the area measured multiplied by the roof pitch and allowing for 8 per m2 divided by 250 screws in a box | ceil(area*1.113*8/250) | boxes |
| Insulation / wool / sarking (18m2 coverage) | How many rolls are required for the area measured multiplied by the roof pitch divided by based on 18m2 coverage | ceil(area*1.113/18) | rolls |
Guttering
Example Parts for 125mm half round guttering Length Measurement:
| Part | Explanation | Formula | UMO |
|---|---|---|---|
| 125mm half round guttering (7m lengths) | How many 7 metre lengths are required of 125mm half round guttering | ceil(len/7) | lengths |
| 125mm gutter brackets | How many gutter brackets are required for the length measured divided by 1.5 metres intervals | ceil(len/1.5) | brackets |
Downpipe
Example Parts for a downpipe Count Measurement:
| Part | Explanation | Formula | UMO |
|---|---|---|---|
| 100mm DVW pipe (6m) | How many 6m lengths are required to complete downpipes when 3 metres 1/2 length (3m) is needed for each downpipe | count*0.5 | lengths |
| 100mm PVC 90° bend | How many 90° bends are required when 3 are needed for each downpipe | count*3 | each |
| 100mm saddle clip | How many saddle clips are required when 3 are needed for each downpipe | count*3 | each |
| 100mm classic expansion outlet | How many expansion outles are required for each downpipe | count | each |
| Downpipe nozzle | How many nozzles are required for each downpipe | count | each |
| (optional) 100mm junction (for 80%) | How many junctions required for 80% of the downpipes needed | 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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