The Grange Barn is, according to the National Trust, the oldest timber-framed barn in Britain and one of the oldest agricultural buildings in Europe. It is a huge structure being 120feet long by 45 feet wide and 35 feet high at the apex of the roof. It was erected by the lay-brothers of Coggeshall Abbey to house the produce that they grew for their community and the earliest timbers date from the beginning of the 12th century. Examination of the type of jointing used on some of the timbers support this date. The barn was extensively re-modelled in the late 14th century and at this time clay tiles were used to replace the thatch.

During the Second World War the barn was used as a centre for Coggeshall folk as the town's community hall had been taken over as a recreation centre for the airmen of all nations who served at the airfields that surrounded this small Essex town. The building survived without significant changes until 1960 when it was taken out of agricultural use and over the next two decades fell into a sad state of dereliction. Local organisations assembled funds to purchase and restore the Barn in 1982 and over the next three years it was carefully repaired using as much as possible of the original material and traditional construction methods.

In 1989 the building passed into the ownership of the National Trust who open the Barn to the public from end of March to mid-October on Tuesdays, Thursdays, Sundays and Bank Holiday Mondays (in the afternoon).