As a general rule outdoor timber buildings / playcentre’s are treated as temporary structures for the purpose of planning permission and so generally permission is not needed.
Each planning authority has its own rules but general planning exemptions for garden buildings are:
- The structure must be less than 4 metres high to the top of a ridged roof if it is to be beyond 2 metres from a boundary. If it has a flat roof the maximum height should be 3 metres.
- The structure must be less than 2.5 metres high if within 2 metres from the boundary.
- The structure should be 5 metres away from the dwelling.
- The structure must not be sited between the dwelling and the main highway.
- The structure does not have a floor area in excess of 30 square metres.
- If the structure has a floor area of more than 15 square metres it should be 1 metre from the boundary.
- Raised platforms must be no more than 30cm above the ground.
If your dwelling is listed or in a Conservation Area there may be local planning differences. A phone call to the local planning department should clarify the situation.The actual process is best managed by yourself as you are 'the customer' of your local planning authority and will find it easier to have an informal discussion with them. Further information can be found at the government planning portal.