GN88 - Vernacular Valleys - Collar-and-Tie

The origins of vernacular valley details began in much the same way as the rest of the roofs and buildings are formed as ways to overcome common problems with the limited resources that were available at the time of construction. It is common nowadays to think of a valley in a roof as an open gutter or trough formed from sheet metal, purposed-made tiles or proprietary fibre glass products, weathering the junction of where two roof slopes meet, historically though, these materials were either not commonly available or in the case of modern products, yet to be invented.