This appears to have been dragging on for weeks now. Regardless of whether the property is rented, surely the logical first step is for the unhappy neighbour to provide evidence of the damage and arrange for the OP and his builder to inspect it? If that hasn't happened then why would anyone spend money on a structural engineer for a few nails in an external garage wall?
The situation as described seems odd. If this is the whole story then I would respond that the neighbour is not being reasonable and that until he allows access you will not be engaging further on this matter. If he will only accept a professional report then he can pay for it himself. Presumably he will have to allow the structural engineer to access the garage, so why not the OP and the builder who put the nails in?
The situation as described seems odd. If this is the whole story then I would respond that the neighbour is not being reasonable and that until he allows access you will not be engaging further on this matter. If he will only accept a professional report then he can pay for it himself. Presumably he will have to allow the structural engineer to access the garage, so why not the OP and the builder who put the nails in?