FLAT ROOF SCANDAL
One of the questions I ask in many of my talks in architecture schools is “How long will our concrete roofed buildings last”. Most of the people say 50, 60 , 80 or maximum 100 years. If they last only that much, then why should we design them? How are they sustainable? Why are we teaching about these concrete buildings if they are going to last only for 50 years? We know very well that the old buildings built with timber roofs are last for more than 100 years and in the present days, there are more methods available to fight termites and fungi growth. The structural engineering field has developed so much to have large span buildings also. There is very little which is being taught about traditional building materials such as timber, lime, earth etc. in our engineering and architecture courses.
In 1972, there was a study in UK which showed that one third of the Government buildings in UK are leaking in spite of the strict quality check and specifications. This study was published as the leading cover story in the Architectural Review magazine and they used the term "Flat Roof Scandal”. Fine cracks are developed in concrete when concrete expands and contracts daily due to the difference in day and night temperature. Over a period of time, these fine cracks let in water and the reinforcement corrosion I will start. This is why many concrete roofs develops leaks after 20 or even 30 years of its construction.
There are various measures which could be done to increase the durability of concrete. When I was studying for my Masters in UK, there was only two or three books on the repair of concrete buildings, but now there are plenty of books written on the repair of concrete buildings.