Quantity Takeoff Discrepancy Between Drawings and Spec
You are estimating a 60,000 sq ft warehouse addition. The architectural drawings show 18 exterior light fixtures; the electrical drawings show 24 in the same locations plus six on a wall that the architectural plan does not depict. The specification requires fixtures rated for a washdown environment in the loading-dock zone (8 of the fixtures). Your supplier quotes the standard fixture at $340 and the washdown-rated version at $520. The drawings note 'verify quantities in field.' Your takeoff software total currently reflects 18 standard fixtures. The project is design-build with a 10% design contingency already carried.
1. Which quantity do you carry, and how do you resolve the fixture-type question?
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Carry the higher defensible quantity and the correct fixture type for the zone.
- Quantity: The electrical drawings govern fixture counts and show 24, including six the architectural plan omits. 'Verify in field' does not excuse a low takeoff; it signals design uncertainty. Carry 24 as the base, and note the six disputed fixtures as a design-development risk. Design-build means you own design coordination, so undercounting is your exposure.
- Fixture type: The spec's washdown requirement governs the 8 dock-zone fixtures regardless of what the drawings label. Price 8 at $520 and 16 at $340: 8 × $520 = $4,160; 16 × $340 = $5,440; total $9,600. The original 18-standard takeoff (18 × $340 = $6,120) understates by $3,480.
Do not average or split the difference. Price the compliant configuration and document the discrepancy so the design team resolves it before construction.
2. How does the 10% design contingency interact with this discrepancy?
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Design contingency covers unresolved design risk, not known discrepancies you can already quantify. The $3,480 gap between the 18-standard takeoff and the 24-fixture compliant configuration is a known cost, so it belongs in the base estimate, not in contingency.
Use contingency for what remains genuinely unknown - for example, whether the six disputed fixtures survive final design, or whether additional dock-zone fixtures get added. If you leave the $3,480 in contingency while also carrying it as a known gap, you double-count. The disciplined approach: move the quantified delta into direct cost, then reassess whether 10% design contingency is still appropriate for the residual risk. Document the basis so the contingency is not silently consumed by a known item.