The other answers may be jumping on your assertion about extensions within 2 metres of the boundary - without knowing the current rules themselves.
These are the current rules in England (don't know what the 'provinces' do about this sort of stuff these days - they may still follow England).
http://www.planningpo...nprojects/extensions/
About 18 months ago the rules were relaxed concerning Permitted Development Rights - that is, small modifications to dwellings that do not need Planning Consent.
Much depends on the height of this extension at the eaves level - he can go up to 3m high.
The other main constraint is that the roof apex can't be more than 4m.
VHG talks about foundations being checked. He is right, is this is nothing to do with Planning Consent - this is Building Regulations, which requires a separate application to the council (and a fee). It is perfectly possible that he does have Building Regs approval for this project (you would not know). Even if he hasn't, if it proves that he didn't need Planning Consent and he didn't get Building Regs approval either, you cannot use this as a reason to get it demolished unless the structure is unsound and dangerous.
Let us know if you require further interpretation what what the 'rules' are on the Planning Portal website I have provided.