Is expansion joint necessary against foundation to prevent problems?
Not usually… if the new concrete has at least one edge that’s not abutted by a wall or another slab… as long as the new slab has a direction it can take to settle… it should be O.K. I usually install expansion felt (or similar) whenever new concrete is poured to a wall but it’s really not necessary. The “control” joints (grooves in the concrete) should be made no less than 8′ apart. We know that concrete will crack… we want to control where it happens.
