7.rat trap bonds

rat trap bond

1. RAT TRAP BOND

2. RAT TRAP BOND Rat trap bond is a brick masonry method of wall construction, in which bricks are placed in vertical position instead of conventional horizontal position and thus creating a cavity (hollow space) within the wall.

3. RAT TRAP BOND Architect  Laurie Baker  introduced it in Kerala in the 1970s and used it extensively for : its lower construction cost (COST EFFECTIVE) reduced material requirement better thermal efficiency than conventional masonry wall, without compromising strength of the wall.

4. RAT TRAP BOND ADVANTAGES : 1. The rat-trap brick wall can be constructed in 8” or 9” Thickness. 2. Its strength is compatible with to standard 9” brick wall, but consumes 20% less . 3. The overall cost saving on this wall compared to the conventional 9” wall is about 26 %. 4.The air medium that is created by the bond helps maintaining a good thermal comfort inside the building . 5.As the construction is appealing to the eye both internally & externally, plastering is not necessary . 6. All vertical and horizontal reinforced bands, lintels (for standard size openings), electrical conduits are hidden inside wall, resulting in better aesthetic appearance without plastering (exposed brickwork)

5. RAT TRAP BOND CONSTRUCTION PROCESS : 1.BASE layer (bottom) and last layer (top) of the wall should be solid (without cavity ). 2.The NEXT layer of bricks should be laid as brick-on-edge in a continuous row, allowing a space of about ½” between bricks . 3. The height of this first layer would be about 4” with the ends of the brick facing the outer and inner face of the wall

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9. RAT TRAP BOND CONSTRUCTION PROCESS : 3 . The 3RD row above the base row of bricks should have 2 bricks laid parallel with each other along the exterior and interior surface of the wall with a cavity between them . The ends of these bricks will be stabilised with the placement of a single brick on edge that spans the width of the wall .

10. RAT TRAP BOND CONSTRUCTION PROCESS : 4. At the base of openings in the wall for windows, a single layer of bricks laid flat must be used. Lintels for door and window openings must have a single row of bricks placed on edge as a lintel support.

11. RAT TRAP BOND CONSTRUCTION PROCESS : Reinforcement bars can be put in vertical cavities at corners and around openings to improve earthquake resistance . Reinforcement bars can be put in horizontally to make lintels and to improve earthquake resistance . Electrical conduits and plumbing pipes, with prior planning, can be put inside cavity for better aesthetics.

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13. RAT TRAP BOND ADDITIONAL POINTS TO BE NOTED : When constructing Rat-Trap walls for a building that does not have internal walls, no additional columns are required for wall lengths up to 15 ’. 2. When constructing a floor slab on such walls – for walls lengths greater than 15’ – brick columns must be used . These brick columns, when used, must be about 13” x13 ” in size, in order to facilitate the placing of the concrete roof on the walls. It best to reinforce each column with suitably sized reinforcement . The above-described specifications would be applicable to a single hall that has no internal walls, but would not be needed for houses with rooms that require internal dividing walls .

14. RAT TRAP BOND ADDITIONAL POINTS TO BE NOTED : 5 .The Rat-Trap construction method allows for two storey construction . 6. It is important that all bricks used should be adequately fired and of uniform sized to ensure consistency of strength and performance . 7. It is necessary to use a cement/sand mix of 1:6 for mortar.