+1 what DBK100 has advised, which has set me thinking...
jericho.ie, one of your neighbours has threatened both you and your wife with physical violence. Never mind what they think you've done, that's not acceptable.
Keeping it on topic I disregarded this issue in my original post but DBK100 has rounded out the discussion. If there's trouble like that brewing, or stewing, waiting to boil over at the slightest provocation, I think you may need to take some steps.
I think you'll find that even if you put things to rights on your side, the mere fact of your builder doing more work may encourage more threats.
Its as well to nip this in the bud but remember, its your word against your neighbours regarding his/her past issuing of the threat.
As a first step, to get this on the record, consider informing your local Garda Community Officer and call in for a quiet chat explaining the situation.
This is a low key reporting method for domestics and civils - low key, as opposed to making a formal complaint and ending up with a squad car arriving at your neighbours door and him vehemently denying the threat was ever made.
As part of your reporting the incident [which you should do in a calm, controlled manner and not lose hte head] you may find your neighbout has been making complaints about parking noise and nuisance to the Gardaí, and naturally this could colour any future involvement by the Gardaí.
The Gardaí may wish to call out regardless to inspect the property and form an opinion as to the cause of your neightbour's ire, so you risk thme arriving anyway - it may make matters worse, but at least its on the record.
Whether you go down this road or not is entirely up to you, but I strongly advise that both you and your wife put the local Garda Station number on your speed dials in case there is another confrontation.
Do not be intimidated by these people.
One other thing - interview your builder and see if the neighbours have "had words" with him on any occassion - I doubt that this threat of violence came out of the blue and there could be issues you need to be aware of before reporting anything to the Gardaí.
HTH
ONQ.