The Aborfield barn from the 1500 utilises a typical medieval cruck frame structure. It was dismantled in 1977 and rebuilt as a museum in 1980 at the Chiltern open air museum where it currently stands.
CRUCK FRAME STRUCTURE
Cruck Frame construction was a typical wood frame construction used in medieval England as early as the 13th century. A cruck blade is a curved beam made from a single piece of wood. This is split along its length to produce an identical pair of blades which are connected together to make a single frame. These frames are then repeated in sequence to the building length required. The lowest horizontal timber beam supports the ends of the crucks.
For barn structures, the space between the frames were often filled with woven split oak panels and upright posts. The green oak is naturally springing, allowing it to be easily woven together. The gaps between the panels allow for the circulation of air necessary for keeping grain dry.
Although typically made from Oak, elm and other locally available timber was used. The roofing material (typically straw) is supported on rafters and split oak battens. The frame is held together by oak pegs with square spurs. Iron connectors were not used due to cost and as the tannic acid in Oak would affect the iron.
The main framework of the barn, including the four cruck frames, is made of oak. The roofing material is supported on wooden rafters, split oak battens run across the rafters. The joints are held together by wooden pegs and each cruck is made from two halves of a split oak trunk. Oak was the preferred material for this type of construction, although elm and other locally available timber could have been used. Green (unseasoned) oak was used in construction as seasoned oak is as hard as the iron tools that were used to work it! The joints were fixed in place by oak pegs. Oak contains tannic acid and this would affect iron nails. Wooden pegs were also cheaper than iron, and easier to obtain. The sill, the lowest horizontal timber, supports the ends of the crucks. The spaces between the parts of the frame are filled with woven split oak panels. These were woven from green oak, which is naturally springy. The woven walls allow air to circulate through the stored produce, keeping it dry.