Jointing and Pointing

Jointing and pointing are used for the finish given to both the vertical and the horizontal joints in external faces of wall irrespective of whether the wall is of brick , block , solid or cavity construction

Brickwork or blockwork is jointed or pointed for 2 reasons:

• To ensure that all horizontal and vertical mortar joints in external brickwork or blockwork are solidly filled with mortar to make them watertight
• For decorative reasons . THe appearance of brickwork or blockwork can be varied considerably by the use of coloured mortar for pointing and by making the kointing and pointing recessed or protruding .
• 
  Differences between jointing and pointing

• Jointing is the finish of the mortar joints between bricks or blocks , in rbickwork or blockwork that is finished fairface example not subsequently covered with plaster rendering or other finish
• Jointing is executed as the brickwork or blockwork is buildt
• Pointing is the finish given to the joints by raking out to a depth of approximately 20mm and filling in one the face with a hard-setting cement mortar which could have a colour additive
• The mortar for pointing is a special mix of lime , cement and sand or stone dust chosen to produce a particular effect of colour and texture
• Pointing is executed as an operation separate from bricklaying
• Pointing can be applied to both new and old brickwork or blockwork

Types of mortar

1) cement mortar (cement-sand )
-1:3 -suitable for brickwork exposed conditions such as parapets and for brickwork in foundations.

2)Lime mortar (lime-sand )
-1:3 -for internal use olny

3)gauged mortars ( cement :lime :sand )

1:1:6-suitable for most conditions of severe exposure
1:2:9-suitable for most condition except those of severe exposure
1:3:12 -internal use olny

• Mortar for general brickwork may be made from a mixture of cement , lime and sand .
• These mixtures combine the strength of cement with the plasticity of lime
• A rich mix of mortar is one in which there is a high proportion of matrix , that is lime or cement or both , to sand as in the 1:3 mix and a weak mix is one in which there is a low proportion of lime or cement to sand as in the mix 1:3:12
• The richer the mix of mortar the greater its compressive strength and the weaker the mix the greater the ability of the mortar to accommodate moisture or temperature movements
• If the mortar is weaker than the bricks , shrinkage cracks will tend to follow the joints of the brickwork , and these are resonably easy to make good
• If the mortar is stronger than the bricks , shringkage cracks will tend to be vertical through the joints and the bricks , thus weakening the fabric of the structure.
  

Mortar for brickwork and blockwork

• It is essential that brickwork and blockwork be laid in true horizontal courses , and the olny way this can be done with bricks and blocks is to lay them on mortar
• Mortar is a mixture of sand and lime or a mixture of sand and cement with or without lime
• Proportioning of the material can be carried by volume or weight
• Mortar should never be re-tempered , and shouls be used within 2 hours of mixing or be discarded

Functions of mortar
-To join the brickwork or blockwork of a wall into one solid mass , thus increasing its strength and stability
TO transfer the rensile comprresive and shear stresses uniformly between adjacent bricks or blocks
-TO transfer up any inequalities of the bricks or blocks
-To make the wall reasonably waterpoof and airproof under ordinary conditions

TO perform its fucntions , mortar must satisfy certain requirement :

• It must have qdequate stregth , but not greater than that required for the design strength
• It must have good workability
• It must retain plasticity long enough for the bricks to be laid
• It must be durable over a long period
• It must band well to the bricks
• It must be able to be produced at the economic cost.
  

Advantages and disadvantages of blockwork

THe main advantages of blockwork over brickwork are :

1. Labour saving (easy to cut , larger units )
2. Easier fixing ( must take direct fixing of screws and nails
3. Lower density
4. higher termal insulation properties
5. Provides a suitable key for plaster and cement rendering

THe main disadvantage are :

1. lower strength
2. Loss resistance to rain penetration
3. loadbearing properties less ( one- or two storey application )
4. lower sound insulation properties .
   

blockwork bonding at junctions

• Concrete blocks are laid in stretcherbond and joined to other walls by block bonding or by leaving metal ties or strips projecting from suitable bed courses .
• Mortar used in blockwork should be weaker than the material of the walling unit ,generally a 1:2:9 gauged mortar mix will be suitable for work above ground level .
• Because the block units are comparatively large , any settlement movement in a wall will show more abvious cracking in mortar joints

blockwork bonding

• Blocks are made in various thicknesses to suit most wall requirement and are laid in strecther bond
• Thin blocks , used for non-loadbearing partitions , are laid in strecther bond wit each block centred over and under blocks above and below
• At return angles , full blocks bond into the return wall in every other course
• So as not to disturb the full width bonding of blocks at angles , for the sake of stability , a short length of cut block is used as closer and infill block
• Thicker blocks are laid in off centre strecther bond with a three quarter length block at stop ends and sides of openings
• THe off centre strecther bond is acceptable with thicker blocks as it avoids the use of cut blocks to complete the bond at angles
• Concrete blocks walls of specially produced blocks to be used as a fairface finish are bonded at angles to return walls with specially produced quoin blocks for the sake of appearance
• THe L shaped quoin blocks are made to continue the strecther bond around the angle into the return walls
• Quoin blocks are little used for other than fairface work as they are liable to damage in handling and use and add considerably to the cost of materials and albour.

QUoin block at angles

material for blocks

1. Clay blocks

• Standard size of 290mm long x 215mm high x 75 , 100 or 150mm width.
• &5mm cavity block is intended primarily partitions
• 150mm cavity block has been used for the inner skin of cavity walls , but also used in the warmer climates countries such as Malaysia as a single-leaf external walling with rendered and emulsioned finish
  
• THey are made from selected brick clays that are press moulded and burnt
• THese hard , dense block are hollow to reduce shrinkage during firing and also to reduce their weight
  
• THey are grooved to provide a key for plaster
• Clay blocks are comparatively lightweight , do not suffer moisture movement , have goof resistence to damage by fire and poor thermal insulating properties

2.Concrete blocks

• Density of a concrete block gives an indication of its compressive strength
• THe greater the density , the stronger the block
• Classification is by compressive strength categoties : 2.8 , 3.5 , 5 , 7 , 10 , 15, 20 and 35 N/mm square
• Density will also give an indication as to the termal conductivity and acounstic properties of a block
• THe lower the density , the lower is the thermal conductivity factors , whereas the higher the density , the greater is the reduction of airborne sound through the block
• For use as a facing material , a wide range of concrete blocks is manufactured from accurate fair face blocks to rough exposed aggregates finishes
  
• Standard concrete blocks are manufacture as solid , hollow or cellular blocks from cement and either dense or lightweight aggregates
• A cellular block has one or more holes or cavities that do not pass wholly through the block
• A hollow block is one in which the holes pass through the block
• The thicker blocks are made with cavities or holes to reduce weight and drying shringkage
• The most commonly used size of both dense and lightweight aggregate concrete blocks is 440mm long x 215mm high
• The height of the block is chosen to coincide with three courses of brick for the convenience of buildings in wall ties and also bonding to brickwork
• For the leaces of cavity walls and internal loadbearing walls , 100mm thick concrete blocks are used .
• For non-loadbearing partition walls , 60 or 75mm thick concrete blocks are used .
• Concrete block or blockwork