Can my neighbours build an extension right up to the boundary?

If the intended extension of your neighbour is within 3m of the boundary, it requires a party wall agreement. Bear in mind that the Party Wall Act may still be relevant if certain works are performed more than 3m away. An example is piling foundations; these can have a significant impact on neighbouring building foundations that are located much further away than the stated 3m limit.

It may be beneficial for you to allow your neighbour to build up to or on the boundary line if you are thinking of building a similar extension yourself. A simple agreement will mean that you can use the wall for part of your own extension.