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 :
1. its lower construction cost (COST
EFFECTIVE)
2. reduced material requirement
3. 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
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.
13. RAT TRAP BOND
ADDITIONAL POINTS TO BE NOTED :
1. 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.
3. 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.
4. 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.
