In one corner of my living room, the subfloor keeps showing signs of water seeping in (water stains). It seems most noticeable after a heavy rain. The walls have no water lines nor spots. There is a bedroom right above this room and it has no signs of water coming in. There is also a basement below this floor with no problems on that level either. There are no bathrooms near this area. This side of the house is the side that is attached to another townhouse. Roofing companies have looked at the roof, the gutters and shingles seem fine. Has anyone heard of this problem before, or have any ideas as to whom I should contact next.