Brick Masonry : Construction Practices

Bricks are bedded in and jointed with mortar. The bricks are laid to any specific pattern known as bonds. The primary object of bond IS to give maximum strength to the masonry and ensure equitable distribution of load. In bonded walls the vertical joints of successive layers of brickwork are staggered and the pattern gives an attractive appearance to the wall face. There are many types of bonds but the commonly used ones are Ule English bond and the Flemish bond which are described here. 

English Bond 

The bricks in the facing are laid in alternate courses of headers and stretchers. The header course is commenced with a quoin header followed by a queen closer (which is a half brick cut longitudinally) and continued with successive headers. The stretcher courses are formed by stretchers having a minimum lap of one quarter their length over the header. The Figure shows details of the comer of a one brick wall and a one-and-a half brick wall and also a stopped end. 

Flemish Bond 

Bricks are laid as alternate header, and stretchers in the same course, the header in one course being in the centre of the stretcher in the course above and below. In this bond, in addition to a queen closer, a three-fourth brick bat has to be used. The Figure gives the details with a stopped end. 

The choice of the bond depends on the situation, function, load and thickness of the wall. A Flemish bond gives an attractive appearance while an English bond is stronger. In our country English bond is used widely for constructing brick masonry. 

Construction 

Bricks shall be adequately soaked in water before use. Wetting helps in removing dirt, dust and ash from the face of the bricks and in spreading of the mortar more evenly under the brick and also ensures better adhesion. It prevents absorption of water by the bricks from the mortar which may cause decrease in its strength. The bricks shall he laid In courses according to the specified bond.

Bricks shall be laid on a full bed of mortar. Each brick shall be properly bedded by slightly pressing so that the brick surface is fully in contact with the mortar. All joints shall be properly flushed and packed with mortar so that no hollow spaces are left. Properly filled joints ensure strength of the masonry and resistance to penetration of moisture. 

The thickness of joints shall not exceed 1 cm. All the face joints shall be raked to a depth of 15 mm during the progress of work when the mortar is still green to ensure proper keying of plaster or pointing. Where plaster or pointing is not to be done the joints shall be finished flush at the time of laying. 

Scaffolding 

In order to construct masonry, scaffolding is used to facilitate the necessary movements of workers. Double scaffolding having two sets of vertical supports shall be used for all important works and also where exposed brick work is to be done. In single scaffolding there is only one set of vertical supports and the wall under construction provides the other support. In such scaffolding, the placing of the poles on the brick work shall be so adjusted that they are on the header course, so that only one header is left out for each pole, which can subsequently be filled up with a full brick. Such holes shall not be allowed in pillars and columns less than one metre wide. 

Curing 

The brickwork shall be cured by constantly keeping it wet on all exposed faces for a minimum period of seven days. 

All connected brickwork shall be taken up together and no portion of the work is left more than one metre below the rest of the work. Where this is not possible the work shall be raked back, according to the type of bond being followed, in a series of steps at an angle not steeper. Leaving such joints vertical with recesses or tooting in alternate layers should not be allowed as this will form a plane of weakness. 

Cutting and Chasing 

As far as possible services such as concealed pipes, conducts etc should be planned with the help of vertical chases, while horizontal chases should be avoided. For load bearing walls, the depths of vertical and horizontal chases shall not exceed one-third and one-sixth the thickness of the masonry, respectively. 

Vertical and Alignment 

All masonry shall be built true and plumb within the tolerance limits specified below : 

1. Deviation in verticality in the total height of any wall of a building, more than one storey height, shall not exceed + 12.5 mm. 
2. Deviation from the vertical within a storey shall not exceed + 6 mm per 3 m height. 
3. Deviation from the position shown on the plan of any brickwork, more than one storey high, shall not exceed 12.5 mm. 
4. Relative displacement in load bearing walls in adjacent storeys intended to be in vertical alignment shall not exceed 6 mm. 
5. Deviation of horizontal mortor joints from the level shall not exceed 6 mm upto 12 m length, and for longer length shall not exceed 12.5 mm in total. 
6. Deviation from the specified thickness of horizontal and vertical joints shall not exceed 3 mm, 

These tolerances are particularly relevant for load bearing walls.