The methods of bonding new brick work with old brick work are : 

(i) Toothing                        (ii) Racking back 

(iii) Block bonding           (iv) Thicknessing 

(i) Toothing : The process of leaving recesses in the alternate courses of the wall at the 

desired place is called toothing. 

It becomes essential to provide recesses when it is proposed to connect a partition wall to 

the main wall of the building. The depth of the recess is kept as 5 cm and length depends 

upon the thickness of the partition wall. The method is adopted for providing a proper bond 

between the existing and new wall.

(ii) Racking back : The process of leaving an off-set of 5 cm in each course of a wall is 

called racking back.

When the full length of the wall cannot be completed at one time, offsets are left in each 

course of the completed portion of the wall. Next day, the surface is cleaned 
and wetted with water before completing and‘ joining other portions. 

(iii) Block Bonding : When a new cross wall is to be joined to old main wall, then a number 

of rectangular recesses are cut in the main wall. The recesses are cut equal in width to 

that of the cross wall, three courses in height and half a brick in depth after leaving a 

space of three courses between them. The new wall is 
then bonded into the main wall after clearing the recesses from all dust and old mortar. 

(iv) Thicknessing : When an old wall is to be thickened, recess 20cm x20cm X 
10cm should be cut in the old wall, at least one for every square metre. The new work 
should then be built against the old and block banded to it at every recess. 
The surface of the old work should be well cleaned, brushed and wetted before the new work 
is added. 

1 comment:

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