Glossaries in print and online
Recording Timber-framed Buildings: an Illustrated Glossary
Council for British Archaeology, 1996. An essential little book, the cornerstone of timber-framed vernacular architecture terminology. Someone should do an app of this. Unfortunately there is no single handy booklet equivalent for masonry.
An illustrated Glossary for the BARD tick-box building summary - a PDF of a very handy concise 6-page guide. It's free.
The Surrey Domestic Buildings Research Group website has an illustrated glossary of terms. Awkward to navigate but some good illustrations, and covers brick and stonework.
Pevsner's Architectural Glossary is an excellent app (£3.99) for tablets and smartphones, based on the Pevsner hardback book which defines and illustrates general architectural terms. But it touches only slightly on vernacular terms. Perfect if you're in a church or a great house though.