Can I erect walls,fences, gates?

Yes, if the following apply:

• The height of any such structure shall not exceed 2 metres or, in the case of a wall or fence within or bounding any garden or other such space in front of the house 1.2 metres.
• Every wall other than a dry or natural stone wall bounding any garden or other space shall be capped and the face of any wall of concrete block or concrete (other than blocks with decorative finish) which will be visible from any road, path or public area, including public open space, shall be rendered or plastered.
• No such structure shall be a metal palisade or other security fence.