Apartment wiring devices · Practical guides
From dwelling-unit quantities to building totals: type schedules, common areas and exceptions
An accurate takeoff for one dwelling unit can still produce an incorrect building total. Before multiplying, check which unit type applies to each dwelling, identify exceptions and keep common-area quantities separate.
Obtain the dwelling-unit type schedule first
Apartment projects usually repeat several dwelling-unit types (e.g. 59A, 59B, 84A) across buildings and floors. The architectural building plans or unit schedule contain a table identifying which type applies to each dwelling unit. Without this table, a rough calculation such as ‘4 dwelling units per floor × 20 floors’ immediately fails on floors containing mixed types.
Check that dwelling counts by type add up to the building’s total dwelling count. A mismatch may indicate an outdated schedule or missing exceptions.
Exceptions that simple multiplication can miss
- Mirrored dwelling units: Quantities may be the same, but identifiers and coordinates differ. Mark the evidence as ‘mirrored from base type’ so locations can be compared.
- First-floor, top-floor and units above a piloti: Identical-looking plans may have different device counts because ceiling or floor conditions differ. Check for a separate plan.
- Corner units and units with extended balconies: Outlet counts depend on whether the balcony is extended. If both extended and non-extended plans exist, check which applies to each dwelling unit.
- Special plans, including accessible and rental units: Wiring-device specifications may differ.
Give exceptional units a separate column in the type schedule and record them as ‘base type + difference’. This makes their quantity differences traceable later.
Separate common-area and dwelling-unit quantities
Wiring devices in corridors, stairs, elevator halls, underground parking, plant rooms and rooftops appear on common-area plans rather than dwelling-unit plans. Combining them in one table forces recalculation when the dwelling-unit count changes. Keep ‘Dwelling units’ and ‘Common areas’ sheets separate and combine them only in the final total. See Examples of omitted common-area wiring devices for frequently missed items.
Example building-total calculation table
| Unit type | Item | Quantity per dwelling unit | Applicable dwelling-unit count | Subtotal | Evidence |
|---|---|---|---|---|---|
| 84A | Double-socket outlet | 18 | 40 | 720 | 84A power plan R1, C01–C18 |
| 84A (mirrored) | Double-socket outlet | 18 | 40 | 720 | Mirrored 84A; mirrored coordinates applied |
| 84A (1st floor) | Double-socket outlet | 19 | 4 | 76 | First-floor plan; added entrance outlet C19 |
Add the subtotals to obtain the building quantity. The dwelling-count column must match the unit-type schedule. Voltix provides quantities and evidence for each unit type, which can populate the ‘Quantity per dwelling unit’ and ‘Evidence’ columns.
Sources and scope
This article provides general guidance on reviewing apartment wiring-device quantities. For project decisions, the relevant drawing legend, revision information, specifications and contract scope take precedence. See our Editorial review and correction policy.
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