Building walls with the rat trap bond

Just in case I’ve got you visualising rodents scurrying about where they’re not wanted, ease your mind; the rat trap bond I’m talking about is simply a method of laying bricks when building a wall.  It’s similar to the common “Flemish” bond but instead of putting the bricks on their face, they are placed on their edges. This leads to cost savings because less bricks and cement are needed which, in turn, reduces the embodied energy of the wall.

The Rat Trap Bond

Bricks are laid on edge to create an air gap between two layers

Laurie Baker took every opportunity to try and make people realise the value of this method but, by and large, the 20-25% saving in brick doesn’t seem to have been appealing enough.  The rat trap method of construction was popular in England until the start of the 20th century but sustained lobbying by the brick-making industry convinced people that that it was not strong enough to build load-bearing walls.

That is rubbish of course; it’s strong enough for one and two storey buildings as has been proven over and over again by Laurie Baker’s lasting work. But masons too are not usually happy about adopting this system and come up with all sorts of excuses to try and avoid it. I have to admit that, till date, I have not pushed hard enough against their inertia but now I’ve just got one more reason to do so.

For the ShKo bungalow at Karjat, I plan to use the rat trap walls and wanted to know just how much difference they would make thermally. Nobody seems to have done a calculation of the difference — at least there was none that I could find. So, armed with some data from thermal calc and the energy evaluation component of ArchiCAD, I tried to do just that.

Taking just a simple 3m x 3m structure with no openings, I ran a calculation for both types of wall. Result: average U-value of the structure’s outer shell dropped about 15% compared to conventional walls and the energy required for cooling also fell by about 8%. The difference was exaggerated because the model had good roof overhangs to shade the walls.

Still, when you think about it, 8% is nothing to scoff at.  In addition, the embodied energy is reduced quite dramatically and, of course, Laurie Baker’s original reason for using the rat-trap bond still stands — the wall is simply cheaper to build.

Now, I just have to go and steam-roll the masons into learning a new technique.


What is Sustainability?

“Nature has enough for everybody’s need; not for everybody’s greed.”
– Mahatma Gandhi

Quoting Mohandas Karamchand Gandhi may no longer be fashionable but these words are more relevant today than they’ve ever been.

Every material used in construction comes, eventually, from the earth. For any architect who cares about nature, that is a predicament to be faced every day. I know it is unrealistic to halt the production or extraction of such materials but we should, at the very least, try and minimise their usage.

A simple example: small structures in India are often built with reinforced cement concrete frames when ordinary load-bearing brickwork (which is about 25% cheaper by the way) would be more than satisfactory.

Nature-friendly Architecture & Design

Nature has an enormous ability to repair herself but when we exceed her capacity to do so, this cycle of restoration and renewal is broken.

Sustainable architecture and design takes into consideration all aspects of construction that affect the environment.

There are many factors that go into making a building nature-friendly:

Using Materials Sustainably

A large chunk of a construction’s carbon footprint is determined by the materials used. For small structures, reinforced concrete (RCC) framing is environmentally expensive and thoroughly unnecessary to boot! I’ve found that load-bearing work usually does a better job.
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Better Design & Construction Methods

Better design is not just about aesthetics. It holistically considers architectural design, landscape & plantation, sustainable systems & climatic conditions,. A well designed construction has minimal negative impact on the site and its surroundings.
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Saving Energy

During its life cycle, a building needs an enormous amount of energy for lighting, heating & cooling. A design that makes good use of naturally occurring sunlight & prevailing breezes goes a long way in saving associated costs.
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Saving Water

Economists have pointed out that future wars will be over water which makes this the most important factor in my estimation. Saving, harvesting and recycling water is far easier than it is made out to be and you often don’t need an expert to get it working.
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Waste Disposal

Disposal of solid waste might not be an architect’s area of expertise but we can play a proactive role by designing for composting pits etc.
[under construction]


If you compare apples to oranges, you will invariably draw the wrong conclusion.

The biggest deterrent to making clients accept sustainable solutions is, usually, perceived cost. That’s because they almost always compare apples with oranges. For example, if a solar heating system is installed for a project, it will naturally raise the initial cost but, if you calculate how much it saves in the medium to long term, you will find that it doesn’t make sense not to fit it. Essentially, green buildings cost less in the long term.

Even as far as basic construction is concerned, green building costs can be made lower than for typical structures. This was amply demonstrated while building Kaya Kalp where, locally available, low-tech materials and labour were used.