Every visible form in the building is made of some kind of material which in its natural state may be rough, smooth, shiny, dull, plain, coloured or patterned. Many building materials currently in use are manufactured in relatively small units, so that as well as their individual unit qualities, assembled collectively they can make larger forms. Bricks, blocks, tiles and wood panels for instance can be assembled to create walls, roofs and floors.

There are practical reasons for using small units in this way, but there are visual options and advantages too. A variation in the selection of bricks for example, can be used to divide a large wall into smaller panels, to delineate the changes between levels or to provide a datum linking together other common features such as window cills or heads. Bricks can be used to create patterning effects or to emphasise or soften the harsh line at the roof eaves and verge. A change in floor finish in a public building is a useful way of guiding people around the building, perhaps delineating public and private space.

Materials may be selected for the uniformity or consistency of their finish such as colour coated steel cladding or glazing. Every part of a wall constructed in these materials will look the same, although it is interesting that direct sunlight or shading can change the apparent colouring. It should be appreciated too that large areas of glazing may be quite dazzling on occasions, but they are sometimes used to advantage by reflecting their surroundings back to the viewer. This can create an interesting image, but may equally cause confusion and concern. Alternatively, the use of a brindle facing brick, or some types of stone such as marble for example, can introduce a mixture of textures and colours offering variety whilst remaining unified and harmonious. Beware though selecting too great a variety of materials and mixing them together, which can often be a mistake, destroying unity and harmony by being over fussy or too busy.