In architecture, flushwork is the decorative combination on the same flat plane of flint and ashlar stone. It is characteristic of the external walls of medieval buildings, most of the survivors being churches, in parts of Southern England, but especially East Anglia. If the stone projects from a flat flint wall, the term is proudwork — as the stone stands "proud" rather than being "flush" with the wall. Flushwork begins in the early 14th century, but the peak period was during the wool boom between about 1450 and the English Reformation of the 1520s, when church building virtually ceased, and building in brick became more fashionable. The buildings belong to the Perpendicular style of English Gothic architecture. The technique continued in occasional use, and saw a major revival in the 19th century, and is still sometimes used in a modern style today, as well as for the restoration or extension of older buildings.
Typical motifs are arcades, chequers (diapering), shields, heraldic devices and letters or whole inscriptions – the picture of Long Melford Church shows arcading at four levels, shields and a long inscription running below the crenellations (naming the merchants who paid for the new church). Many motifs are very similar ro those achieved in carved or piuerced stonework in other areas. The flints in flushwork areas are very carefully knapped (trimmed to shape by chipping) and selected for fit and consistency of colour, often forming a notable contrast in these respects to those in nearby plain wall areas. The stone usually used is a light limestone, often imported by sea and river from Caen in Normandy or other continental sources, which gives a strong contrast with flint that is most often black. Flushwork, and flint architecture in general, is usually found in areas with no good local building stone, and though the labour cost of creating flushwork was high, it was still cheaper than importing stone to build or face the whole structure. Sometimes large areas are covered with chequers or diapering, as at the Norwich Guildhall (below), Gipping Church, or the Victorian St Mary-le-Tower in Ipswich.
The Ethelbert Gate at Norwich Cathedral is one of the most important surviving examples of early flushwork, begun in 1316–17 and completed the following decade. Only nine surviving gatehouses use flushwork, and this one is further distinguished by using it on all four elevations (the heraldic priory gatehouse at Butley, Suffolk of 1325 is another flamboyant early example). The side shown has elaborate patterned flushwork in the top register, which uses selected round flints in the circular motifs. This section was unfortunately restored in the 19th century slightly differently from the original design. The limestone is unusually dominant in the proudwork level with the statue below, where the squared flints are selected for a whitish colour. Below this there are two rows of black flint and limestone chequers.
Porches added to an earlier church often contain showy flushwork, as at the church that is now Chelmsford Cathedral (below). Few churches have flushwork all over the main body of the building like Long Melford (above); as with carved stone decoration it is more common to find friezes at the base or top of a wall, or a decorated parapet (again often a later addition) to the top of a tower.
According to Stephen Hart, there are over 500 English churches with some flushwork. Among the finest not mentioned above are the churches at Southwold, Woolpit, Earl Soham, and several in Norwich. The unique, and odd, East end of the church at Barsham, Suffolk, has a lattice pattern that continues from the window across the whole wall, whose date is highly uncertain.