Construction Input
Inputs fall into three families according to their nature. Materials are the resources that are physically built into the work or consumed on site (cement, steel, brick, water, fuel). Labor is the crew’s work, priced from the actual wage of each category (helper, mason, journeyman) or from the crews they form. Equipment and tools groups machinery, major equipment and small tools, whose cost is figured per hour of use or as a percentage of the labor cost.
By structure, an input can be basic or composite. A basic input is a simple resource that does not break down into others (a kilogram of cement, a helper-hour, an hour of mixer time). A composite input is built from other inputs and handled as a single unit to keep the analyses simple; the classic cases are the crew (which bundles several labor categories into one hourly rate) and site-mixed mortar or concrete (which combine cement, sand, water and labor into a unit of volume). When you use a composite input inside a unit price, it carries the cost of all of its components with it.
In a unit price analysis (UPA) each input appears with its unit of measure, its consumption coefficient (quantity of input per unit of the work item) and its unit cost; multiplying the coefficient by the cost gives the amount for that line, and the sum of every input forms the direct cost. The consolidated list of all the inputs in an estimate, with their total quantities, is the input takeoff (or input explosion), the basis for requisitions and purchasing.
Classifying inputs into materials, labor and equipment is standard practice, and on public works it is required in order to build up the unit prices. Traditional desktop estimating software manages catalogs of basic and composite inputs; in the cloud, Matterial serves the same function by centralizing inputs, consumption coefficients and costs.
Example
In the UPA for 1 m³ of structural concrete: cement, sand, gravel and water are material inputs; the crew of mason and helper is labor (a composite input that bundles two categories); and the concrete mixer is an equipment input. Each one enters with its consumption coefficient per m³ and its cost, and the sum gives the direct cost.
| Item | Unit | Quantity | Unit price | Amount |
|---|---|---|---|---|
| Materials | ||||
| Red clay brick | pza | 42.00 | $6.80 | $285.60 |
| Cement-sand mortar 1:4 | m³ | 0.030 | $2,150 | $64.50 |
| Labor | ||||
| Mason | jor | 0.180 | $520 | $93.60 |
| Laborer | jor | 0.180 | $380 | $68.40 |
| Equipment | ||||
| Small tools 3% | % | — | — | $4.86 |
Frequently asked questions
What are the types of inputs in construction?
By nature they fall into three groups: materials, labor, and equipment or tools. By structure they can be basic (a simple resource, such as a kilogram of cement) or composite (made up of several inputs, such as a crew or site-mixed concrete).
What is the difference between a basic and a composite input?
A basic input is a simple resource that does not break down into others (a helper-hour, a kilogram of steel). A composite input is built from several inputs and used as a single unit; for example, a crew bundles several labor categories into one hourly rate.
What is the difference between an input and a work item?
An input is a resource (material, labor or equipment) consumed while doing the work; a work item is the finished activity that is measured and paid for (a m² of wall, a m³ of concrete). A work item is priced by adding up the inputs that go into it.