Well, basically I'm just looking for an estimate.
It's not like I think that "oh there's construction next door, let's soundproof the room!" I know it's more complicated than that. I'm thinking of it more as a long-term investment, it's this construction that has motivated me to actually start researching it.
Right now I'm living in my grandparent's house which they will be moving out of in about a year, and I guess my sister and I will be inheriting the house.
Most of the rooms in the house are approx. 5x4 meters, plus/minus a meter or two. If I can afford it, I'd like to soundproof at least one of these rooms to use as a studio.
I record mostly vocals, acoustic guitars, and percussion. The rest of my music is usually done with MIDI (sound modules, samples, reason, etc.) When project budgets are low, I also mixdown at home, which I know might sound crazy to some people when I don't have a proper room, but I have managed to get decent mixes w/ my home setup.
laptoppop: what do you mean by "2nd floor -- that means concrete walls are out of the question... "??