Lintels and ‘overdesigning’
How often do we try discussing with the elderly people at home about getting a building done? The general experience is about the difficulties in forging a dialogue, due to differing construction practices from their time to our contexts. We feel there are advances made in these years and many of them feel we are wasting money by ‘over-designing.’
One simple example could be the case of lintels, which are the horizontal monolith members above any opening to support the wall above doors and windows. In the past, these could be with wood or stone, but often we notice there were no members at all – the wall sits directly on the wood frame! The frame takes the load, so why lintels?
Traditionally, carpenters would prepare the door and window frames in advance, before the walls start, such that the requisite seasoning of the wood is complete. As the mason builds the walls, these frames are placed in the centre of wall thickness and the wall continues without any extra lintel member. Even today, we can see such houses standing for centuries. If so, why are we adding the lintel beam, that too in thick and strong concrete?
Lintels help in tying the building laterally and if continuously placed around all the walls provide a horizontal rigidity to the building, which is a compulsory measure in earthquake-prone zones. However, do we need them all the time in all kinds of buildings, including small houses, in places like Bangalore with least risk of earthquakes? Even expert answers may differ, but reducing the lintels as per context and upon structural engineer’s advice is possible. Every concrete lintels need support by shuttering, time for bar bending and concreting, curing with water and such others, demanding time, money and materials. Can we save on this, even if it’s partly?
Once the walls have reached the lintel level, we can place a wood plank as support, place two M.S. reinforcement rods of required diameter across the opening, pour nominal thin screed concrete, place the bricks vertically with the central three bricks forming a wedge narrowing downwards.
This method uses two concepts – that of reinforced brick beam in terms of steel and principles of flat arch in the brick work. On the top of this flat masonry, two more rods can be placed if heavy loading is expected. For opening up to 5 feet wide, this method can be applied with specifications as advised by engineers. As one sees, there are no concrete beams, delay due to formwork or curing and such others.
Today we design with very high factor of safety, a precautionary approach where nothing may go wrong. Understandably, this method very often leads to over designing, as the example of lintels may prove. We can think appropriately, minimise the design to save money and materials. To that end, all the three stakeholders, namely the designers, owners and builders, should think alike towards a cost-effective and eco-friendly building.