Why quantities become inflated: duplicate plans, details and CAD blocks

Six common sources of duplicate counts

1. Enlarged views/details: The same outlet can appear on the floor plan and an enlarged kitchen or bathroom detail. Once counted on the plan, use the detail for verification only.
2. Overlapping blocks: Two symbols may overlap at the same location. They look like one on screen but produce a block count of two.
3. Copies left in model space: A copied plan may remain elsewhere in model space. Even if it is absent from print layouts, it can still be included when selecting all objects.
4. External and nested references: Outlets appear on both sheets if the lighting plan uses the power plan as an external reference.
5. Obsolete devices left after a revision: A device may be added at its new location without being deleted from the old one. Check both inside and outside revision clouds.
6. Double application of mirrored dwelling-unit/type plans: Assigning the same dwelling to two types in the type schedule counts it twice.

How to identify duplicates

• Assign a purpose to each sheet: Identify which sheets govern the count, such as the base plans, and which are for reference only, such as details and wiring diagrams.
• Coordinate-based check: If device coordinates are recorded, look for pairs of the same item with very small distances between them. Overlapping blocks usually have nearly identical coordinates.
• Layer isolation: Count with only the wiring-device layer visible to reduce the inclusion of reference-drawing symbols or symbols from other trades.
• Recheck inside revision clouds: Check visually for obsolete devices left in the revised area.
• Recalculate totals: Check that room subtotals add to the overall total, and that each unit-type quantity multiplied by its dwelling count agrees with the building total.

Record why duplicates were excluded

Retain devices excluded as duplicates in rows marked ‘Duplicate excluded’. Record the identifier they duplicate so you can explain later why a quantity decreased. The Evidence sheet structure is explained in Reviewable Excel quantity schedule format.