The most important feature of the farmhouse, albeit one which is not externally visible, is its internal, wooden, post-and-beam construction which supports the entire building. The frame was originally made of oak, which was very durable, but from the 18th century it was also made from cheaper pinewood. To protect it from damp, the wooden posts rest on a stone foundation about 50 cm high, often made of fieldstone. The non weight-bearing external walls were built as timber frames, the panels of which were originally filled in with willow wickerwork and clay (wattle and daub) and, later, with brick.