The Land Registry can sometimes provide information about accurate locations of boundaries and who is responsible for maintaining them.
Party Wall Act
If you are working on an existing party wall, building a structure astride or directly next to a boundary, or when you are excavating below the level of your neighbour’s foundations, the Party Wall Act is likely to apply.
Garden walls fences and gates
You won’t need building regulations approval to put up a boundary fence, wall or gate, but you should make sure it is safely built.
Brick and stone walls often collapse and can cause injury or death. The Planning Portal gives advice on how to build and maintain them - you may also want to get expert advice.
Generally you’ll only need to apply for planning permission if you want to put up or increase the height of a wall, fence or gate, to over one metre next to a public road, or over two metres elsewhere.
You won’t need it if you’re replacing or taking down an existing fence, wall or gate – no matter how high. The only exception might be in a conservation area.