Builder damaged my foundation

[Jim Lou]

So new construction is being built next to my 120yr old Victorian home in the Manayunk section of Philadelphia. They dug out under my foundation and did not underpin or brace anything and my basement has some cracks and the exterior wall is starting to bow. 

What legal advice would you suggest? I spoke to a lawyer who said it's possible to sue for replacement value and he wants 40%. Does that mean I sue and get 500k he gets 200k and I'm left with a damaged house, 300k and a 220k bank note? Doesn't seem worth it...