Flint was, after brick, the most widespread and typical of all East Anglian building materials. Flintwork comes in various degrees of workmanship and finish. At the simpler end is pebbles that are used for construction. This kind of structure is found round the coast where pebbles occur naturally on the beach. Pebbles are very hard, as any that are easily broken are soon reduced to sand by the ceaseless action of the waves. Only the hardest stones stand up to constant abrasion of the sea turn into pebbles. Inland the flints appear as broken stones, having a natural ‘face’ without any additional work being done. Nowadays expensive properties may be built of pebbles in the belief that they are imitating local buildings of years gone by; but, unless they are near the sea, this is wrong. Inland these builders should be made using more angular stones which, having broken facets, produce a very different looking structure.
Within this general description of ‘pebbles’ there are different types of construction. Starting at the simpler end again there is the “random” pebble wall. This is not as common as you might expect; in fact I don’t believe that a truly random pebble wall exists; there has always been some selection made, so that neither the very small stones nor the very largest ones are used. This type of very simple stone-work is often referred to as rubble, and was commonly used for the unseen interiors of walls in churches. Continuing to greater complexity of construction, the pebbles are closely graded as to size, and to some extent to colour as well. These pebbles are set in courses, with stones of the same size alongside each other, but with each course using a slightly different size.
We now leave pebbles and progress to the the next kind of flint building. This has faceted flints. They can be left more or less as found in both the size and shape; this again is referred to as rubble construction. Normally some work is done with these stones before they are laid, in much the same way as we mentioned earlier with regard to pebble; they are selected for suitability and are not used in an entirely random manner. With these flints they may be “knapped” ( that is struck hard with a hammer) to produce a surface that is intended to be seen. The outer face is knapped, but the outline of the stone is still in its natural state. Even without further work some very fine buildings can be produced using knapped flints, particularly if some thought is taken in placing them to make the mortar courses as inconspicuous as possible.
Lastly we come to squared flints. These are struck in five planes to produce completely regular building blocks. The squared stones are laid in a similar way to bricks. Once again they are selected so that the stones in each course are of the same width, but adjacent courses may be of a different size; or at its most developed stage, a whole section of wall may be produced of matching stones. The mortar courses which are naturally thin in this type of construction are often made almost invisible by the process known as galleting. Here the mortar courses are hidden by the insertion of flakes of flint. There is a fine wall of galleted flint at the Bridewell in Norwich. (Galleting is also found in carstone walling, where the flakes used are of carstone.) The art of knapping flint for building has been lost, and has hardly been used since the middle ages.
An even more delicate form of flintwork is found late medieval ecclesiastical architecture, where the tracery in the windows is reproduced in the walls in freestone, with the glass being imitated in flint. A fine example of this is seen at St Miles Coslany in Norwich. Flint requires the use of some other building material (freestone or brick) to create window openings and the corners of the building. The only shape of tower which lends itself to the exclusive use of flint is a circular structure, which accounts for the many round towers in to be found in Norfolk churches.