Increasing height of a boundary wall

Hi,

Hoping I can pick someone’s brains on general PB planning rules. 

I would like to increase the height of my boundary wall by about 2 feet (for privacy), it is a shared boundary wall (part of it) with my neighbour. Does anyone know about local rules or regulations that may be needed? 

The adjoining wall is on the left of my property as you look at it, are walls like this in Lanzarote classed as ‘shared’ or normally will one of us own the wall (before I check my deeds)?

Thanks in advance for any guidance.

Jason