05.3 · Overheads

Overhead Breakdowns

An OverheadBreakdown is a sub-line inside an overhead item — the same pattern as direct cost breakdowns.

When to Use a Breakdown

Use a breakdown when a single overhead line is made up of several components you want to track separately.

Example — the Site Supervision overhead:

Site Supervision                            (parent)
  L1  Site Manager   26 wk × $3,500 = $91,000
  L2  Site Engineer  26 wk × $2,800 = $72,800
  L3  Safety Officer 20 wk × $2,200 = $44,000
  L4  Admin Support  26 wk × $1,800 = $46,800
                                  Total = $254,600

The parent's total becomes $254,600 — the sum of the breakdown lines — and is read-only.

Opening Breakdowns

Select the overhead and click Breakdowns.
Or Ctrl+B.
Or double-click the row.

Grid Columns

Same as direct cost breakdowns:

Column	Purpose
Item	Component description.
Qty / Unit	Component measure.
Resource	Optional link.
Rate	Rate per unit.
Total	`Qty × Rate` or nested sum.
Formula	Optional spreadsheet-like expression.
Status	Per-breakdown status.

Scoped Formula Context

Breakdown formulas use DefineScope.OverheadBreakdown. Line references (L1, L2) refer to rows within this breakdown, not the main overhead grid.

Project parametrics remain accessible via #var_name.

BuildUpAppliesTo Modes

Same as direct costs:

Mode	Effect on parent overhead
Total	Parent `Total = Σ breakdown totals`.
Rate	Parent `Rate = Σ breakdown totals / Qty`.

Hidden Breakdown Lines

A single breakdown line can be hidden and apportioned into other breakdowns (rare but supported). ApportionmentGroupId on each breakdown row tracks membership in an apportionment group.

Typical Patterns

One breakdown per overhead for cost audit.
Two-level nested breakdowns — trade headers and underlying crew / material rows.
One-line "bulk" breakdowns — used just to surface a formula (= #project_weeks * #pm_rate).