Labour constants may be roughly defined as a guide of “how much work someone can do in how much time”.
In reality, this is not an exact science and requires considerable experience, skill, intuition, historic data and some practical application & risk to define and to implement. There will be variations from project to project, site to site, sub-contractor to sub-contractor … and these can be considerable. One labour-constant will not work in all locations and on all projects,
Project and trade costs may escalate (that is, increase) due to excessive or poorly estimated labour time and costs… And what should have taken 2 days to do, or so you thought and priced for, actually took 5 days … And though the materials quantities may have been calculated accurately and purchased economically, sky-rocketing labour costs, time and delays may have bought all your good-work undone, consequently costing extra.
And so some attempt at estimating and reconciling labour time and costs is needed.
Labour constants are a guide of productivity and may be expressed as a quantity of:
- Hours per unit (or minutes or days per unit); or
- Units per hour (or units per minute or day).
As well as this labour for a specific task, there are other labours or items, such as delivery, transportation, hoisting etc. that should also be considered.
Some labour constant examples are:
| Item | Unit | Labour hours per unit * |
| Placing reinforced concrete in ground slabs | m3 | 1.30 |
| Fix 100 x 75mm ground floor timber bearer | m | 0.15 |
| Hang 9mm thick fibre cement wall lining | m2 | 0.60 |
| Fix vanity basin in place | Each | 0.80 |
| Hang solid core standard door on 3 hinges | Each | 1.50 |
* Excludes – travel, storage, transport, delivery and the like
* Examples only