The house next door...or how to NOT build a house

[Frank S]

"The owners said. . ."; well, that is certainly reassuring. Can they predict weather, Lotto numbers, inflation rates or cost of living too? Rarely will over built custom work [usually not in keeping with local architecture] create an increase.

Unless the area is already strictly custom built homes then by filling a vacant lot which was in all likely hood had been poorly kept then a new addition might in time help property values in a minor way.
But other than removing a detractor of a vacant lot I wouldn't expect a significant increase. What it will cause though if tighter scrutiny by a perspective buyer for even the most minor of repairs to be done before they or a loan institution inspector will sign off on any home being sold in the area.