Hi there can somebody please help me around a year ago we built an extension on to our house which had 2 drains under it at which the builder swears he blocked up any way about 4 months ago we started to get a smell in one corner of our living room its like a sewerage smell the extension is built on to the opposite side of this wall we don't have any smell in the extension at all it has around a one foot thick concrete floor to bring the extension floor level with the main house when I have my heating on [oil heating]or my fire one which has a back boiler the smell is gone but if the heating is off e.g. the knight time the smell is there in the morning and the area the smell comes from is the area were my pipes for the heating comes from my outside tank [under the floor] please can somebody help or put me on to somebody that can help I am in the west of ireland its driving us mad.