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Four Types of Estimates

Many construction projects run into financial trouble at the estimation stage due to a lack of robust cost planning. This typically results in builders producing unaffordable quotes.

A QS is a surveyor who prepares an estimate using the drawings. A QS can also act as a project manager, and can be on the client side or builder side of the project.

Per Unit Rate

A unit rate estimate uses predetermined labour and plant output rates to price the construction activities in a bill of quantities. This can be a very detailed estimate and is usually used for pricing purposes in bidding processes. It is also often used in project evaluation and valuations.

Unit rate estimates can be prepared using many different methodologies. They can be based on an existing database of historical costs for particular work tasks, or reviewed in detail from the Gordian guides with R.S. Means. The cost data can then be adjusted for site conditions, the current level of material and equipment prices, labour and plant rates, and the percentages for main contractor’s profit and overheads.

This estimating method is also known as operational rate estimating or bottom up estimating. It is an iterative process, where the quantity surveyor identifies each construction activity and its associated cost components then calculates these for a number of units of measurement. These are then assembled into large components to add structure to the estimate.

The unit rate estimating approach is particularly suited to larger projects where the estimator has access to historical estimating data for common work tasks. It is a very thorough process and can take a long time to prepare. For this reason it is not as widely used by junior estimators or student Quantity Surveyors on internships.

Plinth Area Basis

Plinth area is a term that you will come across when buying or selling property. It is an important factor in calculating property taxes and can have a big impact on how much space you can use. It can also affect your resale value. Moreover, it can also help you calculate your building’s volume and determine its structural stability.

The term ‘plinth area’ refers to the built-up covered area at floor level of any storey in a building. It includes the floor area of internal and external walls, but excludes balconies and verandahs. The calculation of plinth area takes into account the thickness of all walls, and the space occupied by openings like doors on the plan. It also includes the thickness of plaster along the wall. In addition, the space occupied by supports like central pillars and other such obstacles within the plan are included in the thickness of the wall.

The cost of construction is determined by multiplying the plinth area of a building with its plinth area rate. The plinth area rate is determined by considering the cost of buildings with similar specifications in a locality. It is not a perfect method of estimating the cost of a building, but it provides a good estimate. The other two methods of estimating the cost of a building include Unit base method and Cubical Contents method.

Elemental Estimate

An elemental estimate is an outline assessment of the costs for a construction project, typically used at the design stage. While it is similar to traditional trade estimating, it differs in the way cost is aggregated. While trade estimating summarizes costs to a product, an elemental cost plan presents the cost of each construction component in terms of its underlying “element.”

Using this approach allows greater accuracy than area or unit methods, especially when the estimate is prepared for a specific design requirement. This also allows the designer to identify potential areas of cost savings and more effective management of the project budget throughout its lifecycle.

This type of cost estimation technique is very useful at the early stages of a design when the design is not fully developed. It helps to control costs, as it gives a clear indication of the feasibility of a development and can be updated alongside the bill of quantities (BOQ) at each stage of the design.

However, the limitations of this method are that it requires access to reliable historical data and industry benchmarks, which may not be available for every project. It also relies on expert judgement and knowledge of the project, and can be affected by changes to the scope or design. In addition, it can be difficult to upscale from an elemental estimate to a full BOQ when the designs are finalized.

Detailed Estimate

The detailed estimate is conducted after the Rough Cost Estimate to acquire the Technical Sanction of a project. It involves decomposing the facility into tasks and preparing each task’s design and construction elements. These details are then multiplied by the units of rate to acquire a cost for each item. This method is more accurate and allows for the comparison of prices of similar items from different sources. Accurate rates of materials and construction work are essential to the estimation process. Using inaccurate rates will result in an inaccurate estimate.

To prepare the detailed estimate, you need to know how to read a drawing and be skilled in quantity surveying. It is important to understand the size of each item of the facility and how it relates to the size of other similar items. It is also necessary to abstract data from the drawings. This includes dimensions, heights and lengths of various components. It is also necessary to make deductions for voids and openings.

Once the estimated quantity has been prepared, it is then rated and priced by an estimator using various pricing techniques. This can be done by a QS or an estimator who works for the builder (and normally does the drafting of a builders BOQ plus rating and pricing) and the cost plan is handed over to the contracts team for the building.