Mass-built means that there is no frame supporting the roof; the mass of the walls is the only support. Although this is a common building method today, it requires very precise building and squared masonry or brick.
In the middle ages, most building used a timber frame and only the rich, the landed gentry, aristocracy and the church could afford the labour and materials for mass -built barns. The ones that do survive from this period are the high status ones like Bradford-on-Avon Tithe Barn and Glastonbury Abbey Barn. Very often the walls had to be reinforced with stone buttresses to stop the weight of the roof forcing the walls outwards.
Mass-built barns became more common after the introduction of brick to England by refugees from the Low Countries in the early fifteenth century. As one might expect, this first occurred in East Anglia and London where the refugees first settled. At first bricks were the preserve of the rich, some of the earliest barns being those at Hales Hall, Old Basing and the Cross Barn in Odiham.
As bricks became cheaper and more plentiful they were used to replace wattle-and-daub infill and eventually were used for more ordinary yeoman’s barns. By the nineteenth century, brick had virtually replaced stone and timber for farm buildings in general.
All that is left of The Great Barn at Beaullieu St. Leonards is one massive gable, half of the other end and one and a half walls.
Sketchup model: Pilton Grange Barn. Notice the thickness of the walls. The position of the buttresses corresponds to the position of the raised-cruck trusses.