NEC ECC: People cost justification within SCC audit?

I’m looking for advise on auditing people costs as per the SCC with NEC 3 option E. we are currently supplied rates within the Application for payment and now conducting an audit to turn into actual cost. Staff on the project are mixture of part timers and full time within the Working Areas. Under the SCC payments are due to sickness and holidays. How do we (a) pay for holidays when not in the working area and (b) establish holiday and sickness entitlement of staff that are part time.

Staff (People) cost is calculated based on the time worked while they are within the Working Areas, incurred in order to Provide the Works.

Traditionally this is calculated by assessing the ‘available working time’, that is 365 (or 366) days less 104 weekend days less 8 bank/public holidays to give 253 days. The contracted entitlement to annual leave is then deducted (say 25 days) to give 228 days. Then an allowance for sick leave is made, say 8 days to give 220 days. Other types of leave may be factored in, where this ‘distorts’ the calculation, such as maternity/paternity leave.

The total ‘cost to employ’, as defined by the SCC, is divided by the calculated number of days ‘available to work’. When you then pay for a day you are accruing an amount for days not worked. If a person works 220 days on a project (as per the above calculation) then their total ‘cost to employ’ for that year would be paid, including time off for any of the stated reasons.

Part time staff apply in the same way but on a pro-rata basis for leave allowances.