Much of the Cotswolds and the Severn Valley lie within Gloucestershire, so many of Gloucestershire’s barns are made from the limestones of the region.
“Cotswold Barns” by Tim Jordan and published by Tempus Books is an excellent detailed survey of these barns. “The Great Barn of Bredon - Its Fire & Reconstruction” by F.W.B. Charles is a beautiful book about the great barns of the Severn Valley. Unfortunately it is now out of print but second-hand copies can be found.