In previous blogs we have briefly discussed the sizes and numbers of mud bricks used in the construction of the palace at Malqata; in this blog we are going to discuss the actual bonding patterns – how did they stack bricks to make the palace walls?
To review, there are two main sizes; bricks that are 30 cm long and those that are 40 cm long. The width of these bricks are approximately 1/2 their length and the thickness is about 1/2 the width, although the thickness will vary the least, regardless of the overall size. These proportions vary slightly, but bricks will normally be within a centimeter of these ratios. Recently, we are recording more and more bricks that fall between these two sizes, being 35 cm long and 17 cm wide. We have also found a few bricks, in only one location, that are 27 cm long.
The multiple sizes seems a bit unusual as they do not relate to the function or actual sizes of walls constructed; the same size wall may be made up of the largest or the smallest bricks. One example is the enclosure wall, which is 2.4 – 2.5 meters thick. Mud bricks 30 cm long are used for most of its length utilizing a simple bonding pattern of seven headers and one stretcher (7 x 30 cm + 15 cm + mortar joints). In one section the wall is made of 35 cm bricks with a bonding patten of six headers and two stretchers (6 x 35cm + 17 cm + mortared joints).
Another wall is 1.33 meters thick and made of three headers and one stretcher of 35 cm bricks and another wall of the same thickness made of four headers of 30 cm bricks. In all cases, small variations in the width of the mortar joints will made up any differences.
The most common bonding pattern is two headers and one stretcher for a wall thickness of 0.6 meters. The pattern on the vertical wall surface is always alternating rows of headers and stretchers, unless a mistake is made or there is a need to level a section of a wall – more on this later. We have recorded walls that are one brick wide, two bricks wide, three bricks wide, the most common, four bricks wide and every width up to 10 bricks wide, and then the enclosure walls which are either 14 or 15 bricks wide, depending on the size of the bricks used. The least common are walls that are only one brick wide; these are thin partitions or perhaps even walls that are not full height, as they would not be stable even if they were not supporting walls.
An important character of all the walls is that stretchers are never used on the interior of a wall, only on the edges. A wall is never built with three stretchers as that would require a stretcher in the interior of a wall. A wall that size would always be made up of a header and a stretcher. Even the thickest walls — the enclosure walls — are made up of all stretchers except one or two on the edges of the wall.
One wall was documented that was 0.88 meters thick and the pattern was two headers of 35 cm bricks and the alternating course was two stretchers and one header. In one case there was a gap in the center of the wall of 18 cm that was filled with mortar and mud rubble; the alternate course had two 9 cm gaps also filled with mortar and rubble. In this case, stretchers used in the center of the wall would have eliminated the large spaces between and resulted in a much stronger wall.
A great deal of the variation in the bonding patterns is obvious only under close scrutiny. The most visible variation is on the wall surface when there is a deviation from the standard alternating rows of headers and stretchers. The most common is a brick that is set in the wall on its edge, rather than flat. The principle purpose is to level that and subsequent courses, which have strayed a little from level. The other purpose is is to correct a change in the bonding pattern that may have adjacent rows of headers, rather than alternating headers and stretchers.
On rare occasion we have documented bricks set on edge, but set parallel to the wall axis rather than perpendicular to it. This is perhaps the worst solution possible as this brick might just tilt a little on its edge and fall out of the wall. In this case, although it shouldn’t work well, the fact is that the examples we see are 3,400 years old.
Now, if these were problems faced by the ancient builders, you can bet that in our preservation of the palace we run into some of the same problems of unlevel courses and bonding patterns that don’t match. Well, we do it the same way as the ancients. In the example below we changed from two courses to one course; we did do a bit of sloping of the subsequent course, but in another course, we are level again.
So there we have it. Of course as a preservation project we not only want things to function properly, we also want the character of the original masonry to be reflected in the new protective masonry. By using the same techniques as the ancient builders in our new masonry and using the same bonding patterns, we achieve both.