Construction Economics: A Guide for Quantity Surveyors

Construction economics applies the principles of economics to the building and engineering industry. It asks why construction costs what it does, how prices change, how design choices affect cost and how to compare spending now with costs and benefits later. For quantity surveyors, it is the thinking behind every estimate, cost plan, tender report and investment appraisal.

Construction is a large, cyclical and fragmented industry. Its prices respond to interest rates, public spending, workload and material markets. Each project is a one-off, built on a particular site, by a temporary team, under a contract that shares risk in a particular way. Understanding those forces is what lets a QS give advice rather than just numbers.

This guide covers the economics a practising QS needs. It explains the UK construction market and its cycles, how tender prices are formed, how to use price indices, the economics of design, location and procurement, investment appraisal and the economics of productivity and sustainability. Where ProQS has a detailed guide on a method, this page explains the principle and links to it.

What Is Construction Economics?

Construction economics works at two levels.

• The industry level. How construction output, prices and employment respond to the wider economy, interest rates, government policy and material markets.
• The project level. How design, specification, location, procurement, time and risk determine what a particular project costs, and whether it gives value over its life.

Both matter to the QS. Industry-level economics explains why the same building costs more this year than last. Project-level economics explains why two buildings of the same floor area can cost very different amounts.

The UK Construction Industry and the Economy

Construction is one of the UK’s largest industries. The ONS reported that new construction work in Great Britain was worth about £139 billion in 2025, at current prices, an increase of 1.9% on 2024. In the third quarter of 2025 there were about 376,500 VAT and PAYE registered construction firms and around 1.5 million employees, not counting the self-employed. CITB put the total construction workforce, including the self-employed, at about 2.6 million in 2025.

Several features make the industry economically distinctive.

• Fragmentation. Most firms are small. Large contractors subcontract much of their work, so prices depend on a long supply chain.
• Cyclical demand. Construction demand swings more than the wider economy. It is sensitive to interest rates, business confidence, house prices and public investment.
• Derived demand. Clients do not want construction for its own sake. They want homes, offices, schools or transport. Demand therefore follows the demand for those uses.
• One-off products. Each project is designed and built for a particular site, which makes prices hard to compare without careful adjustment.
• Long lead times. Projects take years from decision to completion, so prices and conditions can change significantly during delivery.

Interest rates, policy and public investment

Interest rates affect construction in two ways. They change the cost of finance for developers and contractors, and they change demand, especially for housing and commercial development. At the time of writing in November 2026, the Bank of England’s Bank Rate is 3.75%.

Public investment is a major source of demand, especially for infrastructure. The government’s 10 Year Infrastructure Strategy, published in June 2025, sets out around £725 billion of infrastructure investment. Policies on housing, planning, building safety and net zero also shape what is built and how much it costs. See our guide to UK construction papers and playbooks.

Labour and skills

Labour is one of the biggest construction costs, and supply is tight. CITB’s Construction Workforce Outlook, published in June 2026, estimates the industry needs about 41,200 extra workers a year from 2026 to 2030, or around 206,000 in total. When skilled labour is scarce, wages and subcontract prices rise and programmes lengthen. This is one reason productivity and offsite methods attract so much attention.

For sources of current market data, see our guide to UK construction market data.

How Tender Prices Are Formed

A tender price is not simply the contractor’s cost plus a fixed margin. It is a market price, shaped by supply and demand. Two different measures capture this.

• Building costs measure what it costs contractors to build, such as labour, materials and plant. The BCIS General Building Cost Index tracks these.
• Tender prices measure what clients pay. As well as costs, they reflect the contractor’s overheads, profit and risk pricing, and market conditions. The BCIS All-in Tender Price Index tracks these.

The two can move apart. When workload is high, contractors can raise margins and choose which projects to bid for, so tender prices rise faster than costs. When work is scarce, contractors cut margins to win work, and tender prices can fall even while costs rise. That gap is a key source of risk and opportunity in procurement. See inflation and price adjustment.

What drives a contractor’s price

For how these factors affect estimates in practice, see factors affecting estimates and cost accuracy and contractor estimating and tender pricing.

Using Price Indices

QSs use indices to bring historic cost data up to date and to forecast prices for the tender date. In June 2026, BCIS forecast that the All-in Tender Price Index would rise by about 15.5% over the five years to the second quarter of 2031, and the General Building Cost Index by about 13.1%. That is roughly 2.9% and 2.5% a year, compounded. Forecasts change, so always use the latest figures.

Worked example: updating a cost rate

This example is illustrative. The index values are invented to show the method. Use published BCIS index values in practice.

A completed school cost £2,450 per m² of gross internal floor area. The tender price index at its tender date was 380. The forecast index for the new project’s expected tender date is 424. Because a tender price index measures prices at the date of tender, the rate is moved from one tender date to the other. Any inflation during the construction period is then allowed for separately, depending on whether the contract is firm price or includes fluctuations.

• Updated rate: £2,450 × 424 ÷ 380 = about £2,734 per m².
• The original project’s location factor is 100 and the new project’s is 95, so the rate becomes £2,734 × 95 ÷ 100 = about £2,597 per m².

The rate still needs adjusting for differences in specification, size, shape and site conditions. Indices adjust for time and place, not for design. See NRM 1 cost planning.

The Economics of Design

Design decisions fix most of a building’s cost long before a contractor prices it. A QS who understands why can give useful advice at the stage when it has most effect. These are the main principles.

Worked example: plan shape and external wall cost

This example is illustrative. The rate and dimensions are chosen to show the principle.

Four single-storey designs each have 1,000 m² of floor area and 4 m high external walls. External walling costs £650 per m², including windows and doors.

The long, narrow plan needs 74% more external wall than the square, adding about £243,000, or £243 per m² of floor area. The square is not automatically best, though. Daylight, natural ventilation, the site, the use and the value of the space may all favour a narrower plan. The point is to know what each choice costs, so the client can decide whether the benefit is worth it. See value engineering.

Location, Procurement and Risk

The same building can cost very different amounts depending on where, how and when it is bought.

• Location. Labour rates, market competition, access and logistics vary by region and by site. Inner London is typically the most expensive UK location. BCIS publishes location factors to adjust for this.
• Procurement route and contract. A lump sum transfers more risk to the contractor and costs more to buy on uncertain work. Target cost and cost reimbursable contracts keep more risk with the client. See construction procurement routes and types of construction contracts.
• Timing. Tendering into a busy market, or before design is ready, raises prices. Programme length affects preliminaries, which are time-related. See preliminaries.
• Risk allocation. Risks placed on the party best able to manage them are usually cheapest overall. Risks pushed onto parties who cannot control them are priced heavily or end in disputes. See cost management and risk management.

Investment Appraisal and the Time Value of Money

Money now is worth more than money later. Construction decisions often trade higher spending now for savings later, such as better insulation, longer-lasting materials or more efficient plant. Comparing them fairly means discounting future costs to present values.

The discount rate

For public sector appraisal, the HM Treasury Green Book sets the discount rate. Following the 2026 discount rate review, HM Treasury accepted a lower rate and published a revised Green Book and updated guidance on discounting in October 2026. The discount rate is now 3.0% in real terms for years 1 to 30, falling to 2.5% for years 31 to 75 and 2.25% for years 76 to 125. The previous schedule started at 3.5%, a rate in place since 2003, so older appraisals will have used higher rates. The same rates apply to all projects. Private sector clients usually use their own cost of capital, which is often higher.

Worked example: capital cost against running cost

This example is illustrative. A public client is choosing between two heating systems over 25 years.

Option B costs £60,000 more to install but saves £8,000 a year, so its simple payback is 7.5 years. Over 25 years, its whole-life present value is about £79,300 lower. At the old 3.5% rate, the advantage would have been about £71,900, which shows how the discount rate affects the answer. A full appraisal would also include maintenance, replacement, residual value and carbon. See life cycle costing and development appraisal.

Optimism bias

The Green Book also requires appraisers to adjust for optimism bias, the systematic tendency to underestimate costs and durations. For QSs, that means building realistic risk allowances into early estimates rather than presenting the best case. See feasibility and quantity surveying.

Productivity, Labour and Offsite Construction

UK construction productivity has grown slowly for decades compared with many other industries. Reasons often given include fragmentation, one-off projects, low investment in technology and the cyclical nature of demand, which discourages long-term investment.

Offsite and modern methods of construction aim to shift work from site to factory, where repetition, quality control and automation are easier. The economics depend on volume and continuity. Factories need a steady pipeline of work to cover their fixed costs. With it, they can reduce programme time, labour on site and defects. Without it, they struggle, as several high-profile modular housing firms have shown. For QSs, comparing offsite with traditional construction means looking beyond the build cost to programme savings, finance costs, quality, risk and whole-life performance.

Sustainability and Whole-Life Value

Net zero has changed the economics of many design decisions. Clients increasingly assess options on whole-life cost and whole-life carbon together. A design that costs more to build may cost less to run, last longer or reduce carbon, which may matter for regulation, funding, letting or reputation. The QS’s role is to put cost and carbon on a comparable basis so the client can see the trade-offs. See sustainability and quantity surveying.

Applying Construction Economics in Practice

• At feasibility, test affordability with realistic rates, inflation and risk, not best-case figures.
• During design, advise on shape, height, grid and specification while change is still cheap.
• At procurement, read the market. Choose a route, a contract and timing that suit market conditions and the client’s risk appetite.
• In appraisals, compare options on whole-life cost using the right discount rate, and test sensitivity.
• Throughout, use current data and explain the assumptions behind every forecast.

For budgeting, cash flow and funding, see financial management in construction. For the QS role more widely, see what is quantity surveying.

Frequently Asked Questions

Related ProQS Guides

• UK construction market data
• Inflation and price adjustment
• Life cycle costing
• Factors affecting estimates and cost accuracy
• Development appraisal
• The future of quantity surveying

Sources and Further Reading

• Construction statistics, Great Britain: 2025, ONS.
• Bank Rate, Bank of England.
• BCIS five-year forecast, June 2026.
• CITB Construction Workforce Outlook 2026 to 2030.
• Green Book supplementary guidance: discounting, HM Treasury, October 2026.
• Green Book Discount Rate Review 2026: HM Treasury response, October 2026.