The beaver builds a chamber in the embankment out of branches and wood shavings, the so-called living quarters. This has a diameter of approx. 60 - 100 cm and can be reached through a tube dug by the beaver. The entrance to the tube is always below the surface of the water to protect it from enemies. This allows the beaver to enter and leave its burrow unnoticed. This simple form of beaver dwelling is called earthwork. The inconspicuous building type is hardly noticeable on a body of water and is often found on steep embankments with soft, diggable soil.
The residential boiler must always be dry. If the water level rises during a flood, the beaver is forced to expand its burrow upwards. To do this, he digs out the top of the cauldron and stamps down the falling soil. To prevent the soil above the boiler from collapsing, the ceiling is reinforced with twigs and branches. In winter, mud and plant parts are additionally applied for thermal insulation. The result is what is known as the central building, which extends above the surface of the earth and is thus recognizable from the outside.
If the water level continues to rise, the typical beaver lodge (building construction) can develop over time. The beaver digs higher and higher, weaving more and more sticks and pieces of wood together, until the burrow is finally above the surface of the earth and consists only of the branches and twigs that it built itself. The castle is cared for and constantly improved by all family members.