FIRED CLAY BRICKS
The most effective technique with clay is undoubtedly firing at high temperature. The clay is thus technologically changed and can no longer return to the primary form, which is still possible with raw clay. Cob, rammed earth and adobe can be crumbled to dust and recreated afresh by the addition of water.
Fired bricks can be used in several compositions, but one principle has to be assured: overlapping of at least one quarter of its length. Use of the whole brick is possible, its half or three quarters. All the bricks have to be placed alternately, what is longitudinal on one side, is transverse on the other, the same as with courses. Each brick can be laid as longitudinal or transverse in a double setting.
Clay bricks do not have to have simple orthogonal geometrical shapes, a clay mixture of higher quality also enables other, thicker shapes. These can be used not only for walls, but for the roof, special windows, decoration etc.
Bricks ensure exact dimensions and relatively sharp edges, which enables controlled compositions. So above all, a considered system of proportion is needed to determine the dimensions of the brick blocks, so that they can be built with the fewest possible different sizes (Juvanec 2010).
The proportion theory has to be introduced as theory, but in practice the first requirement is overlapping.
Modular dimensions are needed for both adobe and fired bricks - as a result of the proportion theory.
The most compatible modular coordination
uses an equation with duplicating numbers:
1, 2, 4
Mathematical expressions are as follows:
1 x 1 =1
2 x 1 = 2
4 x 1 = 4
and
2 + 2 = 4
Only the length 'four' can be divided into two halves or three quarters (Juvanec 2010). If we use simplification of this length with the designation 'one', the other lengths are:
the whole element is equal to 1
half of it is ½
three quarters are ¾, while the smallest dimensions remain as ½ and ¼.
Overlapping has to be at least ¼.
The modular grid for the elements composing a wall starts with and is multiplied by 'one'.
Historical modular systems are still in use, although the dimensions have been changed. A typical brick 1 : 2 : 4 was the same in the Austro-Hungarian system, which used a foot (30 cm), as today, using lengths of 24 cm, divided by half (12 cm) and three quarters (18 cm), with one quarter as its thickness (6).
The proportion system is not a limitation, it allows several widths of a wall, needed for different purposes (Juvanec 2009a). While a vertical position of a brick is not used (it is not constructionally sound enough), a single wall can be composed of half of a brick only for partition walls, with its full length the wall becomes constructionally sound, with three halves even insulating. Thicker walls are possible where necessary, but only in the coordination system by one half (12 centimetres).