Saturday, 10 December 2016

Before You Demolish That Building: Consider Underpinning and Retrofits - Engr. Osaz’ ENOBAKHARE


Building collapse continue to dominate industry events over the past few years. There are many defective buildings waiting to collapse and the owners of some of these buildings are not particularly sure which way to go in fixing the problem. 

Apart from being counter-productive investment-wise and attracting attention in a negative way, having a defective/sick building can cause the owner to be just as sick as it is because of the inconveniences that it brings coupled with uncertainties and strings of complaints. 

What readily comes to mind or the popular advice is ‘bring it down and rebuild’. This demolish and rebuild option is often very expensive and can be really wasteful, even though some others argue that it gives birth to something new. What difference does it make? Using underpinning and retrofits techniques, a defective building can be restored completely and made to look astonishingly new at a much reduced cost.
 

Sometimes owners of such properties are forced to sell them at some incredible prices just so that they do not continue to endanger the lives of the building occupants as well as to avoid incurring the wrath of the law should it collapse. 

But having worked on a couple of defective buildings over time, my team and I have discovered that not as much money and time is needed to put these kinds of buildings back in shape using underpinning techniques as it will take to pull down the entire structure and re-build. 

For instance, it only cost about 8 Million Naira to underpin and retrofit a defective block of 4 flats located on the Lagos mainland completed in less than 7 weeks. However demolishing and rebuilding would have cost not less than 20 Million Naira; that’s a whopping 12 Million Naira difference which is enough to build two units of 3-bedroom bungalows extra. Besides it is common knowledge that it would take a longer time to complete.

 

The cost advantage is far greater in larger buildings. An estimate for the underpinning and retrofits of an existing defective three-floor warehouse shown in the picture (which has tilted by about 75 degrees to the horizontal almost leaning on the nearby building) was pegged at 27 Million Naira (including the cost of all external works) to be completed in 13 weeks but the estimated cost of demolishing the entire structure and rebuilding it amounts to 68 Million Naira. Once the underpinning and retrofit work is completed, it would be vertically upright and renewed.



The technique of using underpinning operations to restore defective buildings is not new, what is surprisingly new is the appreciation of this technique in Nigeria. It’s a similar cost-effective concept as used in other engineering sectors e.g. overhauling a facility using Turn-Around Maintenance (TAM) approach instead of demolition and redevelopment. Again, it has been established that underpinning extends the life span of the building equivalent to new construction and keeps it safe throughout its life span. Isn’t it too hasty to demolish? Talk to a professional Structural Engineer. 

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