Benchmarking & Cost Analysis

Section 1

Purpose

Benchmarking and cost analysis are the twin disciplines that underpin evidence-based cost advice. Benchmarking is the process of comparing a project’s cost, programme, or performance metrics against equivalent completed projects to test whether the current estimate is realistic and to identify where costs diverge from the norm. Cost analysis is the structured recording, presentation, and interpretation of cost data from completed projects so that it can be used reliably in future estimating.

At feasibility stage, benchmarking provides the evidential foundation for the Order of Cost Estimate. At later stages, it enables the QS to test whether evolving cost plans remain aligned with comparable schemes and to challenge design or specification decisions that are driving costs above reasonable norms. The governing RICS publication is Cost Analysis and Benchmarking (2nd edition), which sets out principles, definitions, and best practice for both activities.

The RICS Elemental Standard Form of Cost Analysis (BCIS NRM Edition) — Principles, Instructions, Elements and Definitions (2012) provides the mandatory format for recording and submitting cost analysis data to BCIS. Firms that submit cost analyses to BCIS contribute to the industry’s shared knowledge base and simultaneously demonstrate the data management rigour expected at APC Level 1 (Data Management, ).

Section 2

Key Principles

Cost analysis is structured around the BCIS/NRM 1 elemental breakdown. Elements are standardised categories of building work (substructure, frame, upper floors, roof, external walls, windows and external doors, internal walls and partitions, internal doors, wall finishes, floor finishes, ceiling finishes, fittings and furnishings, sanitary appliances, services, and external works). Using a consistent elemental structure across all projects makes comparisons valid.
The key cost analysis metrics are: (a) £/m² GIFA — overall and elemental; (b) element unit rate (EUR) — cost per unit of an element (e.g. £/m² of roof area); (c) element unit quantity (EUQ) — the quantity of each element per m² GIFA; (d) proportion of cost — each element’s share of the total measured works cost. Together these allow like-for-like comparison between projects of different sizes.
The wall-to-floor ratio (W:F ratio) is a key design efficiency metric. It measures the ratio of external wall area to GIFA. A high W:F ratio (e.g. above 0.6) indicates a complex or fragmented building form that drives up external envelope costs. A low ratio (e.g. 0.3–0.4) indicates a compact, efficient form. The W:F ratio is always recorded in a cost analysis and used when comparing projects.
Abnormal costs must be stripped out of the cost analysis before submitting to BCIS or using for benchmarking. Abnormals — piled foundations, contamination, complex access, listed building, specialist fit-out — are project-specific and would distort the benchmark if included in the elemental rates. They should be recorded separately as an addendum to the analysis.
BCIS adjustments are always required when using published benchmark data. Location factors, Tender Price Index, and specification adjustments must be applied before comparing or using BCIS data on a new project. Raw BCIS rates are base-date historical figures and cannot be used without adjustment.
Employer’s consent is required before using project cost data for external benchmarking or publication. Most appointment forms include confidentiality provisions. The QS should check the terms of appointment before submitting data to BCIS or using a project as a comparator in a published or shared context.
Benchmarking is not just a feasibility tool. It should be applied at every cost plan stage to test the evolving design against comparable schemes. A cost plan that shows a particular element significantly above benchmark warrants investigation — it may reflect a genuine design decision or it may signal an error.

Section 3

Practical Application

Follow these steps when undertaking benchmarking at feasibility stage and when preparing or submitting a cost analysis on completion of a project:

Step 1

Define the purpose and scope. Clarify whether the exercise is: (a) selecting a benchmark rate for an Order of Cost Estimate; (b) testing a cost plan against comparables; or (c) preparing a completed project cost analysis for BCIS submission or internal records. The purpose determines the level of detail required and the data sources to be used.

Step 2

Record the project data parameters. For any meaningful comparison, the following must be recorded for both the subject project and each comparator: GIFA; building type and sub-type; number of storeys; structural frame type; external envelope specification; quality/specification level (budget, standard, high, prestige); location; tender date; procurement route; form of contract; contractor.

Step 3

Calculate and record the W:F ratio. Measure the total external wall area (including windows and doors) and divide by the GIFA. A W:F ratio above 0.6 for a standard building type should prompt a question about design efficiency. Record the ratio in the cost analysis alongside GIFA, NIA, and the number of floors.

Step 4

Prepare the elemental cost analysis. Break the measured works cost into the BCIS/NRM 1 elements. For each element, calculate: total element cost; element cost per m² GIFA (£/m²); element unit quantity (EUQ) per m² GIFA; element unit rate (EUR). Separately list abnormal costs. Record all percentages of measured works cost.

Step 5

Apply adjustments before comparing. To compare one project’s cost analysis with another, or with BCIS, the data must be on a common basis. Adjust for: location (BCIS Location Factor); time (TPI — rebase all comparators to a common date); specification (qualitative adjustment based on brief review). Document all adjustments applied.

Step 6

Identify and investigate outliers. Flag any element where the subject project’s cost per m² GIFA differs from the benchmark by more than 15–20%. Investigate the cause: is it a genuine design decision (e.g. a high-specification facade)? An abnormal that was not separately identified? A pricing error? A scope difference? Document the conclusion in writing.

Step 7

Submit to BCIS on project completion (with employer’s consent). Complete the BCIS Elemental Standard Form of Cost Analysis (NRM Edition). Strip abnormals from elemental rates. Submit within 12 months of practical completion. Retain a copy of the submitted analysis on the project file as evidence of data management practice for ISO 9001 and APC audit purposes.

Section 4

Common Mistakes to Avoid

Comparing unadjusted costs. Comparing a 2019 Inner London project with a 2024 South West project without applying TPI and location factor adjustments produces a meaningless result. All comparisons must be on a common base date and location.
Including abnormals in elemental rates. Piled foundations or complex M&E included in the substructure or services elemental rate will make the rate look high and distort future estimates that use it as a benchmark. Abnormals must always be stripped out and listed separately.
Using too small a comparator sample. A single ‘similar’ project is not a benchmark — it is anecdote. The QS should draw on at least 10–15 comparators from BCIS or the firm’s cost database to produce a statistically meaningful range.
Failing to record the W:F ratio and other efficiency metrics. Without these, the cost analysis cannot be meaningfully compared to others. The W:F ratio, GIFA, NIA, number of storeys, and structural frame type are minimum required data points for any analysis.
Using project cost data for benchmarking without employer’s consent. This is a confidentiality breach. Check the appointment terms before using or sharing project data, even in anonymised form.
Treating benchmarking as a one-stage exercise. Benchmarking at feasibility is the start of the process, not the end. The QS should apply benchmarking at each cost plan stage to ensure the evolving design remains within normal cost parameters for the building type.

Section 5

APC Competency & Quick Reference

This guidance note is relevant to the following RICS competencies under the Quantity Surveying and Construction pathway (December 2025): Design economics and cost planning (Levels 1–3); Quantification and costing of construction works (Levels 1–2); Data management (Levels 1–2). Refer to the current RICS Quantity Surveying and Construction Pathway Guide (December 2025) and the RICS APC Candidate Guide (February 2024) for full competency definitions and assessment requirements. See also the RICS Sector pathways page for updates.

What is the wall-to-floor ratio, how is it calculated, and why does it matter in cost analysis?

The wall-to-floor ratio (W:F ratio) is the total external wall area (including windows and external doors) divided by the GIFA. For example, a building with 3,000 m² of external wall and 6,000 m² GIFA has a W:F ratio of 0.5. It matters because the external envelope is one of the highest-cost elements of a building. A high W:F ratio (above 0.6) indicates a complex or irregular building form that drives up envelope costs relative to floor area. It is always recorded in a BCIS cost analysis and used to contextualise elemental comparisons.

What are the four key cost analysis metrics produced for each element, and how are they used?

The four metrics are: (1) Element cost per m² GIFA — total element cost divided by GIFA; allows cross-project comparison regardless of building size. (2) Element unit quantity (EUQ) per m² GIFA — the quantity of the element (e.g. m² of roof) per m² GIFA; reflects design efficiency. (3) Element unit rate (EUR) — cost per unit of the element (e.g. £/m² of roof); reflects specification and market rates. (4) Proportion of measured works cost — each element as a percentage of total measured works; flags unusual weighting. These four metrics together allow valid benchmarking and outlier identification.

Why must abnormal costs be stripped out of a cost analysis before submitting to BCIS or using the data for future benchmarking?

Abnormal costs are project-specific items — such as piled foundations on a difficult site, contamination remediation, or complex listed building works — that are not representative of normal construction costs for that building type. If included in elemental rates, they inflate the benchmark and will cause future estimates based on that data to overstate costs for projects that do not have the same abnormals. Abnormals must be listed separately so that the underlying elemental cost analysis remains a valid comparator.

Section 6

Feasibility Stage Checklist

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Purpose of benchmarking exercise defined — feasibility estimate, cost plan check, or completed project analysis

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Project data parameters recorded: GIFA, building type, storeys, frame, specification, location, tender date

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Wall-to-floor ratio calculated and recorded

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BCIS benchmark source identified — minimum 10–15 comparable projects, sample parameters documented

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All BCIS adjustments applied: location factor, TPI rebasing, specification adjustment

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Abnormal costs stripped from elemental rates and listed separately

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Elemental outliers (±15% from benchmark) identified, investigated, and conclusion documented

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Employer’s consent confirmed before using or sharing project cost data externally

Section 7

CPD Learning Outcomes

Prepare a structured elemental cost analysis in accordance with the BCIS/NRM 1 elemental breakdown, calculating cost per m² GIFA, EUQ, EUR, and proportion of measured works for each element.
Apply location, time, and specification adjustments to benchmark data and conduct a meaningful like-for-like comparison between the subject project and BCIS comparators, identifying and investigating elemental outliers.
Identify abnormal costs within a project cost analysis, strip them from elemental rates, and record them separately to preserve the integrity of the analysis for future benchmarking use.

Section 8