I want to make what is now a small den into a bedroom. But I need to make it a little bigger. The den is an addition to the house so I know the section of wall I want to move was at one time an outside wall. But it runs parallel to the floor joists above and below. The portion I want to move is only 8' long and I will only be moving it about 18". Should I put in a header where the wall is now? I'd rather not if I can avoid it.