What is a Prime Cost Sum (PC Sum)?
A PC Sum is a budget which is typically set by the Quantity Surveyor which should be expended on the supply only costs for materials or goods.
PC Sums are normally used when the precise quality or specification of those materials and goods are unknown at the time of obtaining a price from a contractor.
An example can be seen below which is an extract from a sample pricing schedule:
| Description | Quantity | Unit | Rate | Total |
| Ceramic floor tiles; PC Sum of £38/m2 | 80 | m2 | £75 | £6,000 |
From this example you can see that a PC Sum of £38/m2 has been allocated as a budget to purchase ceramic floor tiles from a supplier. This is outlined within the description of this particular item.
In this example, the overall rate of £75/m2 provided by the contractor includes the supply costs of the ceramic tiles at the prescribed rate of £38/m2 and also all other costs associated with fixing or installation of the floor tiles.
When the exact specification of the goods or materials is known and an accurate rate can be obtained from the marketplace for the supply of said goods or materials, the overall unit rate (in this case £75/m2) will be adjusted accordingly. This will increase or decrease the contract sum amount and the cost adjustment will be borne by the employer.
It is important to note that a PC Sum is subject to price adjustment and therefore any PC Sums contained within a construction contract hold an element of risk for the employer. Careful consideration should be given regarding their appropriateness and commercial management during project delivery.
