Estimating standards and work breakdown

An estimate for even a small building contains hundreds of items. Without a consistent way to organize them, items get missed, counted twice or priced on different bases, and the estimate cannot be compared with other projects or turned into a cost control budget. Estimators therefore organize their work with standard classification systems and measure it with standard rules. This lesson introduces the two classification systems used across North America, MasterFormat and UniFormat, the Canadian elemental cost analysis format, and the measurement rules that decide how each item is counted.

Why standard breakdowns matter

A work breakdown divides a project into pieces that can be measured, priced, scheduled and controlled. A standard breakdown does the same thing in the same way on every project, which brings several benefits.

• Completeness: a standard list works as a checklist, so the estimator asks about every division or element instead of relying on memory.
• Communication: specifications, subcontractor bids, cost reports and historical data all use the same numbers, so a price for Section 09 21 16 means the same thing to everyone.
• Comparison: costs from completed projects can be stored by element or section and reused, because they were collected on the same basis.
• Control: the estimate's line items become the budget's cost codes, so actual costs can be compared with estimated costs item by item during construction.

Two broad ways of breaking down a building exist, and estimators use both. A trade or work-results breakdown groups work by the materials and trades that produce it: concrete, masonry, metals, wood, finishes. An elemental breakdown groups work by the parts of the building that perform a function: substructure, superstructure, exterior enclosure, interiors, services. The same item of work appears in both, organized differently.

MasterFormat: organizing by work results

MasterFormat is the master list of numbers and titles for construction work results, published jointly by the Construction Specifications Institute (CSI) in the United States and Construction Specifications Canada (CSC). It is the organizing system for project specifications in both countries, which is why bid estimates, which follow the specifications, are usually organized by MasterFormat. The current edition is MasterFormat 2020, with periodic online updates.

MasterFormat uses six-digit numbers in three pairs, such as 03 30 00 Cast-in-Place Concrete or 09 29 00 Gypsum Board. The first pair is the division, the second the level-two section and the third the level-three section, with optional further digits. The 50 divisions, numbered 00 to 49, are grouped into subgroups.

Because MasterFormat follows the way work is bought, it suits bid estimates and subcontract packages: the concrete subcontractor prices Division 03, the drywall contractor prices Section 09 21 16 and part of 09 22 16, and so on. Its weakness for early estimating is that it needs a design detailed enough to know which materials and products will be used, which is not known at schematic design.

UniFormat and elemental breakdowns

UniFormat organizes a building by functional elements: the systems and assemblies that perform a function regardless of the materials used. An exterior wall is an element whether it is brick, metal panel or curtain wall. This lets an estimator price a building before materials are chosen, and lets designers compare the cost of alternatives for the same element. UniFormat is published by CSI and CSC, and the related UNIFORMAT II classification is published by ASTM International as standard E1557.

• A Substructure: foundations, basement construction, slab on grade.
• B Shell: superstructure, exterior vertical and horizontal enclosures (walls, windows, roofing).
• C Interiors: interior construction, interior finishes, stairs.
• D Services: conveying, plumbing, HVAC, fire protection, electrical, communications.
• E Equipment and furnishings, and F Special construction and demolition.
• G Building sitework, and in recent editions Z General, covering general requirements, contingencies and allowances.

In Canada, the CIQS publishes an Elemental Cost Analysis format widely used by quantity surveyors for cost planning and for collecting cost data. It groups elements under A Shell (substructure, structure and exterior enclosure), B Interiors (partitions, finishes, fittings and equipment), C Services (mechanical and electrical), D Site and Ancillary Work, and Z General Requirements and Allowances. Elemental costs are reported both as a total and as a cost per square metre of gross floor area, with an element quantity and unit rate for each element, which makes projects of different sizes comparable.

Moving between the two systems is a routine task. As design develops, the cost consultant's elemental cost plan is gradually replaced by measured trade quantities, and a contractor's MasterFormat bid may be re-sorted into elements so the owner can compare it with the cost plan. Many estimating programs tag each line item with both codes so the estimate can be reported either way.

Elemental analysis also uses element quantities and unit rates. The exterior enclosure, for example, can be divided by the area of exterior wall to give a cost per unit of wall area, and the ratio of wall area to floor area shows how compact the building is. A tall, narrow building or one with many corners has a high wall-to-floor ratio and a more expensive envelope per unit of floor area.

Measurement rules

Two estimators measuring the same drawing should get the same quantity. That only happens if they follow the same rules about what to measure, how to measure it and what to include. Measurement rules answer questions such as: Is concrete measured to the outside of the formwork or net of embedded items? Are openings in walls deducted, and if so, above what size? Is formwork measured by the area in contact with concrete? Is excavation measured as the bank volume or the volume after loosening?

Canadian practice draws on the CIQS's published measurement guidance, including its Method of Measurement for construction works and its standard for measuring buildings by area and volume, which defines gross floor area and related measures. Many contractors also use their own written takeoff standards based on these and on trade practice. When rules differ, the estimator states which rule was used.

Some measurement conventions are almost universal. Work is measured net, as it appears in place on the drawings, and allowances for waste, laps and cutting are added separately in the pricing, so that the quantity reflects the design and the waste factor reflects the method. Formwork is measured by the area of concrete it contacts. Excavation is measured as bank volume, the volume of undisturbed ground, with swell and shrink applied later. Linear items such as base, trim and piping are measured along their length. Count items such as doors, fixtures and anchor bolts are counted.

Cost codes and the estimate structure

A contractor's estimate is organized so that it can become the project budget. Each line is assigned a cost code, usually based on MasterFormat with the firm's own extensions for cost type, such as labour, material, equipment and subcontract. The same codes are used in the accounting system so that timesheets, invoices and purchase orders are charged against the budget lines they belong to.

• Division and section: where the work belongs in the specification, for example 03 30 00 for cast-in-place concrete.
• Work item: the measured item within the section, for example foundation walls, slab on grade or footings.
• Cost type: labour, material, equipment, subcontract or other, so that each can be tracked separately.
• Phase or area: optional codes for building, floor or zone on large projects, so costs can be tracked by location.

Choosing the level of detail is a judgement. Too few codes and problems hide inside large lines; too many and field staff code time wrongly because they cannot tell the codes apart. A practical rule is to break out items that are large, risky or that the firm wants to build historical data for, and to group small, low-risk items.