Database of construction resources, materials and works
19 February 2024Creating a project estimate
22 February 2024Having filled the "Construction Resource Database" with entities, we can now proceed to the creation of calculations that are calculated for each process on the construction site for specific units of measurement: for example, for one cubic meter of concrete, one square meter of gypsum board wall, per meter of curb or for the installation of one window.
To build a 1m² brick wall requires approximately 65 bricks (entity «Sand lime brick»), attribute a cost of $1 each (attribute "Cost per unit"), which adds up to $65. We also need to use construction equipment (entity «JCB 3CX loader») for 10 minutes, which will place the bricks near the work area. Since it costs $150 per hour (attribute "Cost per unit") to rent the machinery, 6 minutes of using it will cost about $25. In addition, 2 hours of labor by a mason-laying contractor will be required, with an hourly rate of $30, for a total of $60.
A company's costing base is similar to a restaurant cookbook: it contains a detailed list of building materials and services required for the operation, just as a recipe specifies the ingredients for a dish
The composition of the recipe-calculations are formed on the basis of the accumulated experience of the company, which has a track record of performing these works: laying tens of thousands of cubic meters of concrete, erecting hundreds of thousands of square meters of gypsum cardboard structures, installing kilometers of curbstone or hundreds of windows.
Just as a recipe describes the necessary ingredients and quantities to prepare a dish, a costing sheet provides a detailed list of all the construction materials and services needed to prepare a particular work.
Dozens and hundreds jobs performed dozens and hundreds of times - give workers, foreman and estimator data on the approximate representation of the work in resources, materials, liters of diesel and labor hours per unit of measurement. These volumetric and quantitative attributes of the entities are entered into the costing systems in the form of tables describing each individual task and work consisting of minimal entities from the resource base.
For each task-work, the volume attribute of an entity is multiplied by its quantity (attribute «quantity» and «bid factor») with the addition of the company's profit percentage and speculation percentage
To obtain the total cost of each entity in the work costing, the cost attribute of the entity is multiplied by its quantity and a Bid Factor. Bid Factor can take into account various factors such as complexity of the work, risks, expected overheads and profit.
Thus, the total price of the entire minimum entity per unit of measurement (square meter, cubic meter or piece) made up of articles reflects both the direct costs of materials and labor and the company's additional costs and margins.
The estimator, acting as an analyst, translates the words of the site foreman into repetitive estimates and describes construction processes through resource entities in the form of a table.
Having these objects, we make a unit costing (metre of concrete, square metre of wall), taking into account the experience of the company, adding only the quantity and the bid factor to get the total cost of each work
Depending on the size of the company, the number of task-work calculations can reach hundreds or thousands. Created calculations are stored in the form of tables - templates for typical projects, which are directly linked to the resource base. If the price attribute of an entity (product, material) changes in the resource base, this attribute is automatically changed in the costing table, which allows estimators to update only the resource base (Figure 3.1-6), while work and task costings can remain unchanged for a long time.
These costing templates are not immutable - a copy of the standard costing template is taken for a new project, and then in this copy certain activities are adjusted to meet the needs of the specific project without affecting the standard costing template. Calculations in order to adapt to individual client requirements and opportunities to increase profitability through speculation, maintaining a balance between maximizing revenue, meeting client needs and maintaining a good reputation for the company.
In some countries, such costing templates, accumulated over decades on a national scale, in order to standardize mark-ups and ensure transparency of the cost of works, are turned into state standards (costing recipes) to be followed by all companies operating in the construction market of a given region in projects with state participation.
