1. Dear *****, there would normally be a period of 6-12 months before a caravan located in the same spot no longer was a temporary structure not needing planning permission and became a permanent structure which needed planning permission. However, the need for planning permission would occur before this period if electricity or water was connected to the caravan so the structure acquired a permanancy.
2. However, be aware that any caravan housing workers on land is an ancilliary agricultural use for which there is rarely, if ever, a refusal. This is because there is clear policy in relation to land that workers and persons farming the land should be able to live on it to provide the necessary labour. So, your prospects of getting refused planning permission are very low. I would be very surprised if you got refused.
3. However, you should liaise with the planning officials from the Council and see what the criteria are for them to grant planning permission. They will have certain strict criteria which have to be fulfilled before they will grant a residential planning use, such as what is going to happen to waste effluent and waste run off. So you need to fulfill these.
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