Underpinning is when the earth beneath an existing foundation is excavated and a new foundation is poured directly under the old one to provide more structural strength and increase the height of a basement. We do this a lot in older homes with basements under 6 feet high when the homeowners wishes to convert the basement to a secondary suite or another full height level of the home. During the process, the house is supported with temporary walls and posts which eventually get replaced with new full height walls and posts, and the deeper foundation. Installing new drain tile around the perimeter of the house is usually one of the last steps of the underpinning process. It is technical and unglamourous work, but something we find very rewarding.
Foundation Underpinning. In order to bring the floor height of the basement down, and provide a full height basement, we needed to extend the foundation lower. This is called underpinning. In order to do this safely, we excavated under the foundation for 5 feet, every 5 feet. We then pour the concrete in two stages.