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Tuesday 19 March 2013

RAT TRAP BOND AS AN ALTERNATIVE TO ENGLISH BOND


English bond:
English bond has two alternating courses of stretchers and headers 

Rat trap bond:
Rat-trap bond also known as Chinese bond is a type of garden wall bond similar to Flemish bond but consisting of rowlocks and shiners instead of headers and stretchers (the stretchers and headers are laid on their sides, with the bed face of the stretcher facing outward). This gives a wall with an internal cavity bridged by the headers; hence the name. The main advantage of this bond is economy in use of bricks, giving a wall of one-brick thickness with fewer bricks than a solid bond. No plastering of the outside face is required and the wall usually is quite aesthetically pleasing and the air gaps created within the wall help make the house thermally comfortable. In summer the temperature inside the house is usually at least 5 degrees lower than the outside ambient temperature and vice versa in winter.


Advantages:
·        Strength is equal to standard 10" (250mm) brick wall.
·        The air medium or cavity created in between the bricklayers helps in maintaining a good thermal comfort inside the building.
·        As the construction is done by aligning the bricks from both sides with the plain surfaces facing outwards, plastering is not necessary except in a few places.
·        Buildings up to two stories can easily be constructed with this technique.
·        In R.C.C. framed structures, the filler walls can be made of rat-trap bond.
Material:
·        Conventional English bond (9’’thk wall) 350 bricks are required per cu. m whereas in Rat-trap bond only 280 bricks are required and also the reduced number of joints reduces the mortar consumption.



Cost saving:
·        In the Rat Trap Bond bricks are placed on edge in 1:6 cement mortar. With this technique there is reduction in cost of the wall by 25%,
(reference- HUDCO)




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