This is "permitted development" on agricultural property, hence no planning approval is required. You should acquire approval within 28 days and then be able to begin construction. You ask for planning approval to build a house after five years. If the land is still used for agriculture, then you cannot start construction without permission. You need to get planning permission if you want to build a house on agricultural land that is not classed as farm buildings. This includes land that was previously built on or has been allowed to become overgrown with trees or hedgerows. The local council can decide that they don't want you to build there so you would need to apply for planning permission. It is a good idea to get planning permission before building anything on your land as this will help to protect your investment if you ever need to sell the property. Planning permission is needed for any building except farm houses. These are already considered to be acceptable uses of agricultural land and do not require further approval from an inspector with planning responsibility. For example, a farmer may build a barn or storage shed without seeking further permission from the local authority. If you want to build a house, then you should discuss this with your local planning office. They will be able to tell you what requirements, if any, exist for such a building.