I live in a georgian type home in Chicago. The north wall in the livingroom and the north wall in the bedroom directly above the livingroom have a damp, musty smell. There are no signs of moisture visible. The smell only seems to come out during the summer months. A new roof (complete tearoff) was installed in 2006. The room next to the livingroom that shares the same north wall is a diningroom. No smell is detected in that room. The room next to the bedroom that shares the same north wall is a master bathroom. No smell is detected in that room either. The north wall in the basement doesn't seem to have the smell however, the basement does have a typical damp smell but nothing overbearing. I live on a street with a slight down hill grade (north side higher than the south side). I bought the home in 2003 and had an addition added to the REAR of the home in 2006. I don't recall when this smell started but I would guess sometime around 2006, possibly after my addition was added. The troubled wall is at the front of the home. Please help!

You can buy or rent a moisture meter to tell if there is any issue other than the smell Moisture Meters & Detectors | Humidity Detectors This could even be a plumbing leak. Do you know where you vent stack is located on the roof, check to insure the boot is water tight.