There’s chapels and then there’s chapels. In the UK the word chapel could be used as a badge of Nonconformity (‘I’m chapel’) but a medieval chapel conceals an amazing variety of meanings. Usually it meant simply a space for a secondary altar, screened off from the rest of the building, as in the Bardolph chantry at Dennington (Suffolk: 1) or at Wiggenhall St Mary (Norfolk: 2). By the end of the Middle Ages, it was effectively possible to buy a chantry chapel ‘off the peg; and the stone Markham Chantry at Newark (Notts: 3) of c.1500 has something of that feeling. Inlarge parishes, complete buildings were sometimes constructed that had no churchyard, but did offer a building that was easier to reach for Mass, such as Langley chapel (Salop: 4) or Heath chapel (ND February 2010). Sometimes the architect produced a building almost indistinguishable from a parish church; witness the flushwork-encrusted Gipping chapel (Suffolk: 5) built in the 1470s by SirJames Tyrrell as a chapel to the now-demolished Gipping Hall.
For more, see G.H. Cook, Mediaeval Chantries and Chantry Chapels, Phoenix House, 1947.