If this is discovered after the contract was signed then the buyer is responsible for obtaining the necessary council approval. If council became aware of this prior to the contract being signed and had previously issued a notice, then the seller must obtain the council approval. If the seller does not then the buyer may pull out of the contract.
If, as a buyer, you are concerned that part of the house or any other structure on the property does not have council approval, we recommend that you insert a special condition into the contract requiring the seller to obtain council approval even if discovered after the contract was signed. If, as a seller, you know that part of the building does not have council approval and the buyers are not concerned, then we recommend you insert a special condition into the contract whereby the buyer acknowledges that council approval has not been obtained for that part of the house.