Inside SIC 43220: The £23.6bn UK Plumbing, Heating & Air-Con Industry

A summary of the Construct365 Sector Intelligence Report on SIC 43220 — the Companies House classification covering plumbing, heating and air-conditioning installation. The full 26-page report, including the ten-operator profiles and the complete technology-stack tables, is a free direct download.

Disclosure: Section 10 of the report examines QuoteAgent, which is a Construct365 product. Both the report and this summary flag that relationship openly, and the report sets out the product's limits alongside its case.

One SIC code, three different industries

On paper, SIC 43220 is a single classification. In practice it holds three businesses that barely resemble each other: a handful of commercial mechanical & electrical (M&E) contractors turning over hundreds of millions; a middle band of small firms running five to fifty staff; and a vast base of sole traders and micro firms — around 38,000 of them — for whom the "office" is a van and a phone.

The headline numbers from the report:

• Market revenue of roughly £23.6bn a year, spread across about 45,000 enterprises.
• Concentration is unusually low. The four largest operators account for only around 6–8% of revenue (CR4). The top thirty together hold about a quarter. Nobody controls this market.
• Margins are thin and bimodal. Commercial M&E contracting typically runs at 1–3% pre-tax, while domestic service-and-repair niches can reach 8–15% — both inside the same code.
• Roughly four-fifths of firms employ fewer than five people.

Labour, not demand, is the binding constraint

Demand in this sector is comparatively defensive: repair and maintenance work carries on regardless of the cycle, and regulation keeps generating installation work. The constraint is people. The trade workforce has been broadly flat at around 118,600, while national policy assumes a ramp to 450,000 heat pump installations a year. The report's blunt observation is that this arithmetic cannot work without either a step change in training or a substantial productivity gain per engineer — and productivity is the cheaper, faster lever.

The heat transition compounds the problem at the quoting stage. Where a boiler swap can be priced from a quick look at a cupboard, a heat pump requires a room-by-room heat loss survey, an emitter schedule, cylinder sizing and grant paperwork — potentially days of unpaid pre-sale effort, at win rates that haven't moved.

A technology estate with a hole in the middle

The report maps the software actually used across the sector's three tiers, and finds the estate is bimodal:

• The top ~400 commercial firms run professional tooling — BIM and design suites, dedicated estimating packages with live supplier pricing, construction ERP — and can spend well into six figures a year on software.
• The ~5,800 SME firms are served by a genuinely competitive field-service-management market (job scheduling, certificates, invoicing, accounting sync).
• The ~38,000 micro firms run on a phone camera, a messaging app and — increasingly, thanks to Making Tax Digital — a cloud accounting subscription.

What none of these tiers has is tooling for the step between walking a job and sending a price. Estimating software assumes drawings and a full-time estimator; field-service software assumes the price already exists. The report calls this the quoting gap: the most frequent commercial act in the sector — performed on the order of ten million times a year — is still done from memory, usually in the evening.

Why quoting is where the strain concentrates

The report's seven "strain points" — the admin tax, late payment, price-led competition, compliance load, heat-pump pre-sale costs, subscription fatigue, and the AI adoption gap — converge on quoting more than on any other task:

• Surveys consistently put trades admin at seven to eight hours a week, done in the evenings — and pricing, not invoicing, is where most of it goes.
• Responsiveness decides work: homeowners can't judge workmanship in advance, but they can judge who quoted first.
• Vague pricing is where scope disputes and unpaid extras start — and an accepted quote is a binding contract under the Consumer Rights Act 2015.

Construction is also the UK's lowest AI-adopting sector, with adoption among small construction firms measured as low as single digits. The report argues the barrier is knowledge and workflow fit rather than willingness — which is why it assesses tools that use inputs tradespeople already produce (photos and a spoken walkthrough) as the right shape for the problem. That is the context in which the report discusses QuoteAgent, and it is equally frank about the limits: a quoting tool is a wedge, not a full stack, and it depends entirely on the quality of the firm's own price book.

The structural takeaway

The report closes on a simple structural read: in a flat-growth, thin-margin market, value accrues to whoever controls a channel (a customer base, a framework, a parent's order book) or a scarcity (accreditation, offsite capacity, trained labour). The 41,000 smallest firms can buy none of those. The one lever genuinely available to them is the productivity of their own unpaid time — and the quoting evening is the biggest single piece of it.

Get the full report

The complete 26-page report covers the market map, size-band economics, the ten largest operators with individual profiles, the full three-tier technology-stack tables, the seven strain points with their published sources, and the outlook for consolidation, data-centre demand and the heat transition.

Download the SIC 43220 Sector Intelligence Report (free — no email required)