Solid ground floors of a house extension

Junctions between the ground floor slab and the external walls are usually hidden from view by the skirting board. However, air can leak through the small gap under the skirting board, causing a cold draught across the floor. In some cases, a dirty mark may result as dust is filtered by the carpet along the perimeter of the room.

Gaps and cracks in the ground floor can allow air and, even more importantly, ground gases (e.g. radon and landfill gas) to be drawn into the home. They may develop in solid floors as the concrete cures and shrinks away from the walls. While these small cracks do not necessarily pose any structural concern, they do provide air leakage paths.