Rat trap bond

What is 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. Architect Laurie Baker introduced it in Kerala in the 1970s and used it extensively for its lower construction cost, reduced material requirement and better thermal efficiency than conventional masonry wall, without compromising strength of the wall.

Constructing brick wall using rat trap bond

Rat trap bond wall construction

The bricks are placed in vertical position, so that 110 mm face is seen from front elevation, instead of the 75mm face (considering brick of standard size 230 X 110 X 75 mm). Since width of wall remains 230mm, an internal cavity is created. This is where approximately 30% Material (brick and mortar) is saved and thus overall construction cost is reduced. Cavity provides effective thermal and sound insulation. This makes rat trap bond energy and cost efficient building technology.

Rat trap bond wall corner details

Advantages of using rat trap bond

1. Cost-Effective Construction

Since rat trap bond uses fewer bricks and less mortar than traditional masonry, it leads to significant cost savings. This makes it a preferred choice for budget-conscious projects without compromising on quality or strength.

2. Enhanced Thermal Insulation

The air gaps created within the wall act as natural insulators, helping regulate indoor temperatures. This reduces the reliance on artificial cooling and heating systems, making rat trap bond brickwork highly energy-efficient.

3. Environmentally Friendly

By minimizing the use of materials and improving energy efficiency, rat trap bond brickwork significantly lowers the environmental impact of construction. This technique aligns perfectly with green building practices and sustainable architecture.

4. Aesthetic Appeal

All vertical and horizontal reinforced bands, lintels (for standard-sized openings), and electrical conduits are concealed within the wall, enhancing the aesthetic appeal by eliminating the need for plastering and allowing for an elegant exposed brickwork finish.

5. Structural Strength

Despite using fewer materials, rat trap bond walls offer excellent load-bearing capacity. When executed correctly by skilled masons, they provide durable and long-lasting structures.

rat trap bond window

Things to consider while using rat trap bond

Bricks should be of good quality with consistent size and straight edges First layer (bottom) and last layer (top) of the wall should be solid (without cavity).
Layer at sill and lintel levels of opening and sides of opening should be solid (without cavity) for fixing frames.
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.