The pile is built so that it extends well beyond the surface of the water. Once this pile is made, the muskrats swim underwater and begin to chew out two or three tunnels towards the centre of the pile. When it chews its way above the water level, the muskrat makes a room called a chamber. This chamber is above water level so that it is dry. The muskrat's lodge is not nearly as strong as the beaver's lodge but does provide some protection and warmth for the muskrat.
Muskrats often expand or add to the lodge-type home.
After a number of years, they may have many rooms or chambers. As winter approaches, as many as 12 muskrats may share a lodge home that has been enlarged. The bank dens are located along the sides of ponds or slow-moving streams. The bank den is built by digging into the side of a bank. The entrance or opening to the den is underwater.