Friend and I are having a disagreement on cover (ruins specifically) I was under the impression that nothing would be a -1 to hit rolls unless specifically said under the weapon. My friend says that if it's an infantry unit in ruins that it will be a -1 to hit rolls on them AS WELL as the +1 bonus to cover saves. I looked and didnt find anywhere on this. Is this a house rules thing?

TL;DR Do things shooting infantry in ruins have a -1 to hit?