If you want to build a garage on your property, you should give due courtesy and at least inform your neighbour. If you are living in close proximity with neighbours, they will be disturbed by banging and pounding and it is just right that you inform them how long this is expected to go on. You might also alter their view or block sunlight from their favourite windows.
It is your right to build a garage or any structure within your property, but it is in good form to at least prepare your neighbour of the changes that may affect them.