Thursday, 15 January 2009


Stone masonry

Igneous rock, sedimentary rock, metamorphic rock

Cement mortar or cement-lime mortar
Except for extremely weak stones, the compressive strength of masonry structures is not dependent on the stones but the mortar bonding the stones.

Solid masonry walls
Load bearing walls consisting of stone blocks bonded to a rubble pattern
Composite masonry walls
Load bearing walls consisting of stone blocks bonded to a brick or concrete backing
Stone facing
Non-load bearing facing wall consisting of thin pieces of stone secured by metal cramps to the load bearing wall

Rubble patterns
Random rubble
This consists of stones of all sizes roughly rectangular but not dressed. The stones are not laid to horizontal courses. The small stones are used to fill up the voids between the larger stones.

This pattern is made from stones of different shapes and sizes without much order. The pieces fit together fairly well.

Coursed random rubble
The stone work is laid roughly in courses. It is leveled at certain heights to an approximately horizontal surface.

This pattern is made from uncut stones placed in rows called courses.

This consists of stones accurately worked to plane surface with sharp right angles. The stones are laid truly horizontal. Ashler is used mainly for facing. Very expensive.

This pattern is made of cut stones that fit together, but are not in rows.

This is a pattern of cut stones that fit together and are placed in rows.

Like the mosaics of ancient Rome, this is a pattern of different stones that fit together very well.

Brickwork & blockwork
A walling unit not exceeding 337.5mm in length, 225mm in width, or 112.5mm in height
A walling unit exceeding in length, width or height the dimensions specified for bricks.

Standard format of bricks
Designation Length Width Height
225X112.5X75 215mm 102.5mm 65mm

The nominal dimensions include the thickness of a mortar joint equal to 10mm.
4 courses to 300mm (12’’).

Manufacture of bricks
Clay (silica and alumina) mixed with water, moulded and pressed to shape, dried and then fired to form brick units.

Varieties of bricks
Common bricks
For non-structural uses, such as partitions
Facing bricks
Architectural finish
Engineering bricks
Dense bricks conforming to defined limits of strength, for structural uses, such as load bearing walls

Compressive strength of bricks
Engineering bricks
Class A 69.0N/mm2
Class B 48.5N/mm2
≅5N/mm^2, strength unimportant

Mortar for bonding brickwork or masonry is composed of cement and sand, with or without lime. The addition of lime improves the workability and bonding properties. It also reduces the tendency to crack.

Cement mortars
Note: 1:3 means 1 part of cement to 3 parts of sand by volume. A small quantity of lime may be added.

Cement-lime mortars
1:3:12 used for internal non-load bearing walls
Note: the proportion are cement: lime: sand by volume

Cement mortar with plasticizer
(Plasticizer for improving workability)
1:6 used for non-load bearing external walls
1:8 used for non-load bearing internal walls

Bonding of brickwork:
Header - A brick which is laid in a way that only the short end is visible in the wall

Stretcher - A brick which is laid in a way that allows only the longer side of the brick to be exposed.

Stretcher bond-stretchers in every course
Stretcher bond is the most widespread pattern found in modern buildings. It has become the popular choice for cavity walls with half-brick thick outer leaves because it makes the maximum use of whole bricks, minimising the requirement for snapheaders or for cutting bricks on site. Stretcher bond is thus quick to lay and, overall, is the most economic bond pattern.
Aesthetically, however, stretcher bond has come to be regarded as somewhat bland. To relieve this, there has been a resurgence of interest both in using the more traditional types of bond patterns and in enlivening the appearance of stretcher bond by introducing designs in bricks of contrasting colors. A typical example of the latter is the highlighting of a diamond pattern in stretcher bond. This reflects an effect achieved historically by incorporating flared headers - bricks which had been accidentally overfired, producing a different colour - and is particularly successful in the modern context when blue bricks feature as the contrast. The opportunities available by using polychromatic brickwork to enhance the appearance of a building are the subject of ARCHIFACTS Decorative Brickwork. It is also possible to achieve some degree of variation in stretcher bond by using quarter- or third-lap instead of the more common half-lap.

Each joint is above the middle of the lower brick. It has a low strength in the transverse direction and is used for thin walls only.

Header joint-headers in every course
It provides excellent strength in the transverse direction but longitudinally it is not so good. It is primarily used for walls curved in plan.

English bond
It consists of alternate courses of stretchers and headers.

English Bonding - A brickwork pattern in which the headers and stretchers form alternate rows.

Flemish bond
It consists of alternate headers and stretchers in every course, each header being centrally placed between the stretchers above and below.

Flemish Bonding - A brickwork pattern in which the headers and stretchers alternate in every row.

Fire resistance
Clay bricks withstand temperatures in the region of 1000℃ or more without damage, but under very severe and prolonged heating, the surface of a brick may fuse. Spalling can occur with some types of brick particularly of the perforated type.
A loadbearing wall exposed to fire will suffer a progressive reduction in strength due to deterioration of the mortar in the same manner as concrete. Severe damage is more likely to be caused by the expansion or collapse of other members.