60 K should get you a decent single storey extension, especially
as you’re outside dublin, I have heard of builders building extensions
for €100 per sqft but in dublin I've also seen prices of €220 per sqft.
you really should find a builder you know/trust or at least someone
you could be recommended to talk to. The cost of your works will
depend on a number of factors - finishes, ground conditions, planning
restrictions (if applicable) site constraints etc. the list is endless.
good luck