I was faced with the responsibility of examining the consultant’s submission on fence cost. Like previously stated in my previous week blog, the consultant never did a design for a retaining wall along the swampy part of the fence line. We were now left with no other option than to prepare our estimate and invite technically qualified bidders.
In preparing the estimate, the following were adopted:
WBS: This was clearly absent in the earlier estimate; as this had the entire work lumped into a single work package and was not suitable for project management and measuring of work progress. [1] A WBS was made to create the cost breakdown structure with external perimeter solid, external perimeter see-through, retaining wall and internal boundary sections as Level 1. Each work package broken down further into Level 2 using CSI masterformat of Division Two - Existing conditions, Division Three – Concrete, Division Four – Masonry etc.
Estimating costs: We had detailed design concluded and ready for commercial bid. A Class 1 (AACE) or Unit price estimate was adopted because of the level of definition available (detailed design). The design drawings and specification were carefully studied to come out with a comprehensive bill of quantities (BOQ). The following was carried out to arrive at the BOQ.
>Quantity Takeoff: After going through the design and specification, takeoff for materials and work item done. This involved scaling, counting and calculating of materials and work items via a Quantity sheet. The quantities arrived are tabulated for pricing purpose.
>Unit costing: Pricing of the unit cost was the next step after quantity takeoff. This involved two types namely direct costs (labour, equipment, material and subcontract costs associated with each work item ) and indirect cost ( taxes, site/office overheads, profit and contingencies associated with the work item execution)[2]
The estimate met everyone’s satisfaction and budget approved for the fence. The unpriced BOQ was sent out for contractors to bid on.
In preparing an estimate, i recommend that the estimator should have a clear understanding of the scope, be able to interprete design and specification. This allows for reliable estimate after the application of the estimating principles of takeoff and pricing.
References:
1. Giammalvo, P. D. Day 2: AACE Certification Prep Course November 2010.
2. RSMeans Estimating Handbook, 3rd Edition
3. Pearl Garden Estate BOQ, Monigha Idubamo January 2011
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