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Brick bonds 

The way the bricks fit together in a wall is called the bond, and it creates the visible pattern on the surface of the wall. It was the ability to spot different bonds while walking around a town that first got me interested in brickwork. It's a bit like learning to recognise different trees or different birds. FIrst you just learn to give them names, then you learn why they are as they are.

Solid wall bonds

 Centuries ago, builders discovered that walls, which were more than a single brick thick, would be more stable if some bricks were laid along the line of the wall and some along the wall. Bricks laid along the wall show their sides (stretchers) and those laid across the wall show their ends (headers). At first builders mixed them at random, but then they developed regular patterns or bonds. Over the years different bonds emerged, driven by considerations of strength, cost, ease of laying and fashion. A significant cost factor was the proportion of bricks that would be visible on the outer surface of the wall. If they were, then they needed to be high quality 'facing' bricks, but those hidden within the wall could be cheaper low quality bricks.

Bond Pattern Notes Fraction of facing bricks Click images to enlarge
Flemish Each course has alternating headers and stretchers, with the headers aligned with the stretchers in adjacent courses. More common in England than in mainland Europe 67% (2/3) Flemish Bond
English Alternate courses of headers and stretchers, with the joints in the stretcher courses aligned More common in mainland Europe than in England. Often used in high status buildings 75% (3/4) English Bond
    Often used for bridges and industrial buildings where strength is important   English Bond
English Cross Alternate courses of headers and stretchers (like English Bond) but with the joints aligned with the centres of the bricks in alternating stretcher courses Common in mainland Europe, and also known as Dutch Bond (Kreuzverband in German). 75% (3/4) ENglish Cross Bond
    It is rare in England, where it often suffers from 'Northeast cracks' running along the diagonal lines of weakness.    ENglish Cross Bond
Garden Wall Three courses of stretchers alternating with one course of headers   63% (5/8) Garden Wall Bond
Sussex Each course has three stretchers alternating with one header Also called Flemish Garden Wall 57% (4/7) Sussex bond
'Long Sussex' Each course has five stretchers alternating with one header   55% (6/11) 'Long Sussex' Bond
American Five courses of stretchers alternating with one course of headers More common in America than in UK 58% (7/12) American Bond
Monk Each course has two stretchers alternating with one header. In Common Monk Bond, Headers alternate ¾ brick length left and right on successive courses 60% (3/5) --
  In Symmetrical Monk Bond, the headers are aligned centrally between the stretchers on adjacent courses   Monk Bond (symmetrical)
  In Raking Monk Bond, the headers in successive courses are aligned 1¾ length one way and 1¼ length the other way   Monk Bond (raking)
    Raking Monk Bond creates diagonal stripes that are visible from a distance, as in this example   Example of raking Monk Bond
Some examples show little pattern in the relationship between the headers in successive courses, like this example.   Monk Bond
Header All bricks are laid across the wall, showing headers but no stretchers The only bond where all bricks are visible on the eternal surface. 100% (1/1) Header Bond
The small unit makes elaborate patterns possible with different coloured bricks, but this is not always exploited, as in this example   Header Bond
Combinations Some buildings combine more than one bond, for example terrace houses with front and rear walls in Flemish Bond, and the large end walls in Sussex Bond. Sussex Bond is cheaper to build than Flemish, but weaker. Strength is less critical for end walls, which are normally plain, than for front and rear walls with many door and window openings. Flamish + Sussex Bonds

Hollow wall bonds

During the transition between solid walls and cavity walls, several hollow wall bonds appeared. Some used special bricks, but most were formed by laying the bricks on edge. The thickness of the wall is still the length of a brick, but the bricks laid along the wall now take less than half its width, leaving a gap between them. These bonds were called 'rat trap'' (presumably because a rat could get into the spaces). They are also called Rowlock or Chinese bonds.

The commonest form of Rat-trap Bond is equivalent to Flemish Bond, but the principle can be applied to any bond (except Header Bond). The pictures show several examples. Click on the images to enlarge.

Rat Trap Bond (painted over) Wokingham
Rat Trap Bond (showing cavity) Wokingham
Chinese Monk Bond
Chinese Sussex Bond Wokingham
Chinese Sussex Bond (showing cavity) Wokingham

Cavity walls

Modern walls normally have a single outer leaf of brick, with a space separating it from the inner leaf. Cavity walls had an air gap until the late 20th Century, but this is now usually filled with foam, and modern walls are built with a layer of insulation between the two leaves, rather than an air gap.

With a single brick thickness the only way to lay the bricks is along the wall. This gives Stretcher Bond, where every course has just headers. Stretcher Bond has a monotonous appearance compared with solid wall bonds. When cavity walls were introduced in the early 20th century, this was often offset by using half bricks to emulate the appearance of Flemish Bond. That was costly, and since the 2nd World War Stretcher Bond has become ubiquitous. It is even used for solid walls in gardens, etc, with the two skins tied together with the metal brick ties used in cavity walls.

In the late 20th Century, some architects re-introduced the use of simulated solid wall bonds  (by using half bricks) in some high status buildings, but they haven't restricted themselves to Flemish Bond (see below).

 Also in the late 20th century, architects have relieved the monotony of Stretcher Bond by using courses or patterns of different coloured bricks .

Outside of UK, it is quite common to stagger successive courses  of Stretcher Bond by ¼ brick rather than ½ brick, which also breaks up the pattern, but this is less common in Britain. Click on the images to enlarge.

Stretcher Bond using coloured bricks - Reading
Stretcher Bond with staggered joints - Iceland
Sussex Bond with raised headers - Worcester
Chinese Flemish Bond - Darwen College Cambridge
Chinese Sussex Bond - Sidney Sussex College Cambridge

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