Where I came to a halt is when I asked myself, how am I going to connect 240V AC to a relay that is welded to a protoboard.
Relay has +5mm clearance between the pins,
but protoboard has much less.
I would try soldering, less chance of melting the relay or burning down the house :p
2,54mm or 100mil to be exact
But yeah, on proto boards with mains voltage I drill out and remove copper from pads next to mains pins. So not only between pins but all around. That way I know for sure it will stay away from the low voltage side.
Google found this reference.