NEC ECC: Working Area Overhead Percentages - Inclusions/ exclusions

I have been working with the NEC3 for about 7 years now and only now am I working on my first project where a Working Area Overhead percentage is being used. There seems to be remarkably few posts on this topic and I wonder if someone has some advice or knows of a reputable publication which clarifies what items of cost should be included within the percentage. The Schedule of Cost Components states:

"The charge includes provision and use of equipment, supplies and services, but excludes accommodation, for

Catering, medical facilities and first aid, recreation, sanitation, security, copying, telephone etc, surveying and setting out. computing and hand tools not powered by compressed air"

On first read this seems quite straight forward but when I consider such things as fencing, engineers, cleaning, water, sewage disposal etc it becomes more complicated.

For example:

Is site fencing classed as security if it protects only against theft?
Does the regular emptying of a cess pit constitute a charge under ‘Charges’ or does it fall under sanitation?
While surveying and setting out are Engineers providing services or are they paid for under People (time spent working on site)?
Are cleaners considered under people or WAO percentage?

Your assistance would be appreciated.


The WAO leads to many an argument. Thankfully in ECC4 it will be no more. Coming back to ECC3.

The opening statement to the SCC states “…An amount is included in only one cost component and only if it is incurred to Provide the Works”

This means that depending on the item it could be included in the SCC in more than one way - but only once.

  1. Security fencing - SCC cost component 2 Equipment
  2. Cess Pit emptying - a service under sanitation SCC44(d)
  3. Surveying and setting out - SCC44(h) - a company providing a service? or a Subcontractor clause 17 “…provide a service necessary of the the works” or if your own people then People 1 plus Equipment 2 or 44(h)
  4. Cleaners - again probably a service under SCC44or if your own directly employed people People 1

It really does all depend on how you wish to recover the costs. In Managing Reality Book 4 - their is a comparison between a traditional prelim build up for a contract and ECC - this provides food for thought

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