Multiply the amount the ridge is extended by the height from the eaves (usually the top of the facia board) to the top of the ridge by the entire width (from the face of the eaves at the front to the face of the eaves at the rear of the building assuming it is a side Gable. I'm not sure why you are using a measurement from the front of the eaves to the apex centre line unless it is a half gable) Divide the total by 6. Planning uses a more sophisticated formula but this technique will give you a volume within 1.5%. All measurement taken externallyDoes anyone know how to calculate the volume for a hip to gable roof conversion. extending the ridge by 4.5m the height is 3.2m and front of eaves to the centre line (under the apex) is also 4.5m.
Can someone provide a definitive formula if one exists? I'm not saying that either of the two calculation methods are right or wrong btw. Up to you which one you use. The divide by 6 rule gives you a calculation tolerance in your favour.
1. Is there a universal formula councils and applicants should use to calculate volume for hip to gable conversions? If not, are there multiple ways of calculating a volume that would be acceptable to both sides or could be discussed on that basis? Not Multiple but there are a few. Why bother. If your drawings are accurate & the altered area dimensioned the council will in most cases accept your submitted calculation.
2. Does the council's calculation method over rule any other method automatically? Does an applicant have to prove under their formula that the volume is correct? Not that I know of but it easier to accept their calculation as gospel ( unless they have made an obvious mistake ) Just design the area to fit into their requirements.
3. How would you consider the eaves in the equation? Front & back remain in place and side (end of terrace) have been removed? It's safest to measure facia to facia front to back. The council are interested in the overall external size.
Thanks!
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