Measurement of quantities for construction works.

Measurement of quantities for construction works.

 

Definition of measurement – Measurement of quantities for construction works.

 

Measurement of quantities for construction works is the transformation of drawn information into descriptions and quantities, undertaken to value, cost, and price construction work.

 

It is not just about a quantity surveyor producing a bill of quantities for contractors to price during tendering. It is used in both pre- and post-contract work, helping assess the likely cost of the works, and determining what contractors and subcontractors should be paid for work that has been completed.

 

Pre-contract measurement

 

 During the early design stages, the quantity surveyor  will measure the dimensions of the building to produce budget estimates, perhaps based on bench-marking against similar buildings.

 

As the design develops, they will measure more detailed approximate quantities for cost planning purposes, ensuring that the design can be achieved within the budget.

 

The quantity surveyor then measures the completed working drawings to produce a bill of quantities. Contractors tender for the job by pricing the work described in the bill of quantities.

 

Post-contract measurement

 

The contractor may use measurement for:

 

The quantity surveyor may undertake measurement for:

 

 

Levels of detail for measured information

 

 The degree of detail to which construction work can be measured varies according to its use and the stage in the project. In the very early design stages, there is not much detail available, so estimates are based on general parameters, such as:

 

As the design progresses and more information is known, estimates can become more detailed, such as elemental estimates (for walls, floors, roof, frame, etc.).

 

During the later stages of the design, the work required to construct the building may be measured by:

 

 

Taking off

 

The term ‘taking off’ refers to the process of identifying elements of construction works that can be measured and priced. Those elements can be measured in number, length, area, volume, weight or time, then collated and structured to produce an un-priced bill of quantities. This process is sometimes referred to as ‘working up’.

 

Standard measurement conventions

 

Always measure gross building area and then deduct items such as exterior walls to find floor space area. Always measure on the centre line of the material.

 

 Calculating girths and centre lines

 

The centre line is half way between the external girth and the internal girth.

 

Centre line (CL) = (Internal girth + external girth)/2

 

CL = Internal girth + (No. of corners) x 2(wall width)/2

 

or

 

CL = External girth – (No. of corners) x 2(wall width)/2

 

 

 Calculating girths for irregular shaped buildings

 

CL = Internal girth + (No. of corners) x 2(wall width)/2

 

Number of external corners = 5

 

Number of internal corners = 1

 

External corners – Internal corner = 4

 

This occurs regardless of shape providing the walls encompass 360°.

 

In the example above, the internal girth was 8.00, and the external girth was 10.00.

 

Difference = 2.00 m = 4 x 2(wall width)/2

 

 

Buildings with an inset

 

Girth = 2(length + width) + 2(depth of inset)

 

= 2(6.00 + 5.00) + 2(2.60)

 

= 27.20 m

 

 

BIM

 

Increasingly, software packages are available to assist in the preparation of preparation of bills of quantities, and building information modelling systems can be used to produce bills of quantities from information already contained within the model.

 

At Take off Bill, we use the latest Bill of Quantities software when Taking off construction works. This ensures Accuracy, Efficiency and Transparency, our motto here at Take off Bill.

 

We produce Take off’s and Bills of Quantities for all aspects of construction. No Job is too big or small. We typically work for Developers, Architects, Main Contractors, Sub Contractors and Home Builders.

 

Feel free to contact us here at Take off Bill at plans@takeoffbill.com or check out our website at http://www.takeoffbill.com .

 

P.S. In relation to this post, we tried to upload some really useful images to help explain the measurement process, but they would not upload, sorry guys!!

 

 

Measurement of quantities for construction works.

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