Once when trying to benchmark piling costs with available information from various in-house projects, the data showed an apparently inexplicable variation in the $/m rate for the piling works. In some cases, it showed 2-3 times the $/m rate for the same diameter, and in other cases, the data showed similar $/m rate even though the diameters varied between projects.

After the initial failed benchmarking exercise, I started considering the technicalities of piling and understood that there are different kinds of piling specified for various projects depending on different soil and project conditions. I realised that I was making the mistake of comparing the $/m rate of different piling types used in different projects. This wrong comparison had created the above-mentioned variations in the overall rate.  At this point, I separated the available data into the various types of pilings. That was a good start, but then I did not have enough data points for the individual piling types to be able to generate any sensible benchmarking curves.

But benchmarking was needed for the estimate approval process.

To meet this need, I developed a small estimate model to calculate the rough $/m cost for various types of piling and for various diameters. I assumed an indicative length of pile to generate the graph. I used indicative material and labour rates, norms and productivity factors to calculate the cost of the various types of piling. I included an indicative hiring cost of piling hammer or rig as required for a specific type of piling work. All these inputs and assumptions could be modified for specific project and location to help generate a customised benchmarking graph. I have also assumed a total number of pile for this specific example and would caution that the per meter rate could substantially vary if the total quantity is significantly different. But this still gives an idea and relative cost differences

The attached file shows the proposed working.

Piling Rough Estimate Model for Benchmarking-Rev0 (free resource)

This shows how the costs could possibly vary with diameter and piling type and can be used as an in-house estimated benchmarking graph. Any past project data (if available) could be superimposed on this graph for easy comparison. Any contractor bids can then be compared against this graph to demonstrate the reasonableness of market pricing. This can also help the engineers choose and compare more than one piling type, if technically suitable, to use in a project.