Last fall we got a new big sliding door to our garden deck. During the winter we had problems opening it, probably due to frost heaving. Our carpenter suggested we should insulate the outside of the concrete slab that the house is built upon. This concrete is also a nasty cold bridge into the house floor. So I got the spade out and started to dig.
The concrete slab is about 50 cm ( 2 feet) deep, at least around the perimeter. I also removed the lower plank to make sure to expose all of the concrete.