You need the permission to build a wall straddling the boundary, since unless you were both exercising your right to build, only one would be building and part of that would be on the other's land.
Demolition of structures directly abutting a habitable house does not require permission where this is done as part of an exempted development, but in demolishing his half of the boundary wall you would not be covered vis-á-vis his house.
That is my strict interpretation of the regs and this could be challenged, for example, is a garden party wall that directly abuts a habitable house part of that house.
The building regulations would say not, the planning regs seem to be unclear, and whether a wall is a building is not defined - someone please correct this if needed.
For €80 you could seek a Section 5 Declaration - word it specifically and carefully to describe your position, depending on whether you can get the owner's agreement on this.
There is one Act and 00 Statute you should be aware of.
The Land and Conveyancing Law Reform Act 2009:
http://www.landregistry.ie/eng/Legi...land_and_conveyancing_law_reform_act_2009.pdf
Chapter 3 Party Structures
Statutory Instrument 235 of 28
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P4 the section on the new Class 50 limitations.
ONQ.
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All advice on AAM is remote from the situation and cannot be relied upon as a defence or support - in and of itself - should legal action be taken.
Competent legal and building professionals should be asked to advise in Real Life with rights to inspect and issue reports on the matters at hand.