Quantity survey of a work: what is taken into account how to calculate it?

Ever since man has been building shelters, he has been concerned in the first place to plan the type and the amount of materials essential, to carry out his work: he establishes a meter. When, over the centuries, construction diversified, became specialized and then became an art, the use of professionals capable of analyzing, evaluating, planning, quantifying and then estimating the costs of tasks increasingly complex and specialized becomes an undeniable necessity. Alternately Surveyors in Eastern Antiquity, Surveyors under the Roman Empire, Surveyors in the Middle Ages and Quantity Surveyors during the Western Industrial Revolution, these specialists, today “Technicians in Construction Economics (TEC)”, carry out economic, statistical, commercial and control missions, before, during and after the works.

Units of measurement used for the quantity

In order to avoid misinterpretations, each interlocutor in the construction chain must use a common language, understandable by all without ambiguity. At the base of this virtuous chain are measures. On the plans, as in the measurements or the estimates, the units of measurement are codified in an immutable way:

• unit of lengththe metre receives 2 decimal places after the comma (2.15 m);
• unit of surfacethe square meterreceives 2 decimal places (2,15 m²) ;
• unit of volumethe cubic meterreceives 3 decimal places (2,150 m³) ;
• unit of weightthe grammereceives 0 decimal (2,000 g), on the other hand, we put 3 decimal places for a weight expressed in tons (2,150 t) ;
• unit for calculating labor timetime receives 2 decimal places (2,15 h) ;
• unity monetary for our country, the Euro, receives 2 decimal places (2,15 €).

When the unit is non divisiblewe round to upper whole number (2.15 or 2.55 bricks = 3 bricks).

For the rounding of decimals:

• remove all digits following the last remaining decimal place, when the first digit to be removed is equal to or less than 5 (2,1543 m = 2.15 m or 2.1543 m³ = 2,154 m³).
• When the first deleted digit is equal to or greater than 5the last kept decimal is rounded up to the next higher unit (2, 1556 m = 2.16 m or 2.1556 m³ = 2, 156 m³).

Note : in the building measurements and estimates, the hours are not counted in the sexagesimal system, but in the decimal system (2 h 30 min = 2.50 h).

What are the elements taken into account for the meter?

The quantity survey is established taking into account all the materials and equipment making up the batch (from the smallest screw to the most massive concrete blocks and their possible reinforcement), as well as the estimated labor time necessary for their Implementation.

To carry out this mission, the TEC has:

• for buildings in projects, detailed plans and specifications, specific to the work, this quantity is often called “dbefore measurement” ;
• for renovation work or control and verification missions, the quantity surveyor carries out a precise dimensional survey of the structures in place. The requirements of the specifications apply to this statement.

To avoid confusion, the mathematical calculations of surfaces and volumes must always be carried out in the same conventional order, i.e.:

• length x width x height;
• length x width x thickness.

It may be useful to provide some details on the quantity survey. For this purpose, common abbreviations placed before the data concerned are used, such as:

• mes = measure or measured;
• lg = length;
• l = width;
• ht = height;
• squeeze = thickness;
• h = hour;
• min = minute ;
• DO = dimension in work;
• TO = starter rating, etc.

How to establish the quantity of a work?

To avoid omissions or duplicates, the quantity survey is always established following the chronological order of execution of the work. Here again, the words used and the quantity surveyor’s theoretical and in-depth knowledge of construction techniques and types of materials are extremely important.

Fundamentals of the terms used to understand quantity measurements:

• l‘work qualifies it building to be built completed, as it is to be delivered to the customer;
• the building owner is the clientowner of the work;
• the project manager is the entity in charge of conception and some coordination works (architect or similar);
• the lot is a fraction of the workdetermined analytically by trades or entrusted to a company.
• L’elementary work is the smallest fraction you lot ;
• The floor area (article R.112-2 of the town planning code), is the surface close et covered taken into account to define the building area, local taxes and duties. Close to the living area, it results from the accumulation of each level of the dwelling;
• l’footprint (article R. 420-1 of the town planning code), is the surface totale of the projected building at ground level. It includes closed or open parts, covered or uncovered, including projections, loggias, balconies, lean-tos, sheds, carports, courtyards, etc. Terraces at ground level and roof overhangs not supported on the ground, however, are not counted. This area is taken into account to define the administrative authorization formalities applicable to the building (prior declaration of works or building permit) and the compulsory use of an architect (≥ 150 m²).

The overall bill of quantities of the work is obtained by compiling the bills of quantities and bills of quantities and estimates for each elementary work (OE). The EOs are themselves broken down into sub-elements including base materials (MATCH), the equipment necessary for their implementation (CHAP), accessories and consumables (MCONS) and labor time (MO).

How to present the quantity sheet?

The quantity sheet is presented in the form of a table. As such, the use of a spreadsheet is convenient. There are many “Open Source” spreadsheets that are free (OpenOffice, starOffice, KOffice, etc.) or commercial (Excel, Lotus, etc.) and professional software, more or less complex, specialized in making measurements. You will also find, easily, online, concrete examples of presentation of measurements. These tools greatly facilitate calculations and are (or can be) configured to obtain a personalized presentation of the final document.

The sheet must include a title (or a reminder of the title for the divider sheets), the contact details of the prescriber or the client, the date and a pagination comprising the number and the overall number of pages (eg page 1/3).

Then one numbering specific by line pour :

• the lot concerned (ex 00 – structural work);
• the general item studied (eg 01 – Earthworks and foundations);
• each sub-element of the item (eg 01-10 General earthworks);
• ventilation elementary books (ex 01-10-10 – Excavations in trenches, by mechanical device, earth evacuated).

Nothing prevents adding as many subdivisions as necessary, numbered according to the previous logic.

The sheet must then include at least columnsto register:

• the previously mentioned numbers;
• the designation of the position and/or the brief presentation of the work;
• as many columns as operations performed, with the type of operation (number of elements if several are identical, measurement 1, measurement 2, measurement 3, sub-totals, etc.);
• the unit of measurement used (m, m², m³…) ;
• the final results for each elementary structure;

Depending on the spreadsheet or quantity survey software used, you can, of course, automate the calculation sequences. Also include a line “report” at the bottom of each sheet. This data to be reported must be entered at the top of the next sheet and be synchronized to accumulate data of the same nature.

Creation of the estimate

To produce the estimated bill of quantities (DQE), all you have to do is create a specific sheet synchronized with the quantity survey, including:

• The number of each position concerned;
• the precise description of the services, by elementary work;
• the unit of measurement used;
• the quantities delivered;
• the unit price excluding tax;
• the amount excluding VAT of the elementary work;

then below, a summary frame framed final, including:

• the total amount excluding VAT;
• the applicable VAT rate;
• montant total TTC.