How do i correctly generate or create a Lightmap for a very complex object?

Since not every wall is made per room ( img: http://puu.sh/cKUT4/b3fea0fc88.png ) would that give any problems in the lightmap, and would i have to make every wall specifically per room so the inner walls’ lighting has no weird lines or hard edges? i’m trying cluster the UV faces up correctly now but this has been bugging me… Thanks for responding so quickly!