COSHH assessments for construction: what they are, why they matter, and how to do them properly (2026)

The mistake that fails more COSHH submissions than any other

Here is the single most common reason a contractor's COSHH paperwork gets rejected by an SSIP assessor or pulled up by an HSE inspector: a folder full of safety data sheets, and not a single actual assessment. The safety data sheet is the manufacturer's hazard information about the product. A COSHH assessment is your document about how you use that product, who it puts at risk, and what you do to control that risk. They are not the same thing, and one cannot stand in for the other.

It is an easy mistake to make. The safety data sheet looks official, it lists the hazards, it runs to several pages, and it feels like it ought to be enough. But it describes the substance in the abstract. It cannot know that your operative sprays it onto scaffold fittings in a half-enclosed bay with no extraction, or brushes it on outdoors for two minutes at a time. That gap - between the generic hazard and your specific use of it - is exactly what a COSHH assessment exists to fill, and exactly what an assessor is checking for.

This guide explains what a COSHH assessment actually is, why it is a legal requirement regardless of whether you are chasing an accreditation, what a proper one has to contain, and where they most often fall down.

What COSHH assessments are, and why they are the law

COSHH stands for the Control of Substances Hazardous to Health Regulations 2002. The regulations require any employer whose work exposes people to substances hazardous to health to assess the risk and put controls in place before the work starts. This is not optional, and it is not tied to membership of any accreditation scheme. A sole trader who has never heard of CHAS or SMAS still has the same legal duty as a national contractor.

The purpose is straightforward: to protect the people doing the work. Occupational ill health from hazardous substances is not a rare or historic problem. The HSE estimates that thousands of people die each year from past exposures to substances at work, and many more live with conditions like occupational asthma, dermatitis and silicosis that were entirely preventable. Cement dermatitis, silica-related lung disease and solvent exposure are all live risks on ordinary construction sites today, not relics of a less careful era.

SSIP schemes such as CHAS, SMAS and Constructionline check that you hold adequate COSHH assessments as part of their accreditation, and an HSE inspector can ask to see them at any time. But it is worth being clear about the order of things: you do not write a COSHH assessment for the assessor. You write it because the law requires it and because it protects your workers. The accreditation check is a consequence of doing it properly, not the reason for doing it.

The sections a proper COSHH assessment must contain

COSHH does not prescribe a rigid template, but a suitable and sufficient assessment has to demonstrate that you have identified the hazardous substance, assessed who is exposed and how, and put effective controls in place. In practice that means the following sections. The order matters less than the content.

Substance details. The product name, the supplier, the safety data sheet reference and date, the physical form (dust, liquid, vapour, paste, aerosol) and the hazard classification - the CLP hazard statements, the signal word and the components that drive the hazard. This is where the safety data sheet feeds in: it is the source of the hazard information, sitting inside the wider assessment.

The task. What the substance is actually used for, where, how often, for how long, and in what quantity. This is the section that makes the assessment yours rather than generic, and it is the section assessors scrutinise hardest. "Applying solvent-based adhesive during flooring installation in an occupied office, up to two hours per visit, daily" tells an assessor you have thought about the real exposure. "Adhesive - used as directed" tells them you have not.

Persons at risk. Your own operatives, apprentices, other trades working nearby, building occupants and members of the public where relevant. Spray drift and vapour do not respect the boundary of the person holding the can.

Routes of exposure. Inhalation, skin contact, eye contact and ingestion, and how each could occur during this specific task. This is one of the three sections most often left out, and leaving it out is a reliable way to fail an assessment.

Health effects and exposure limits. What harm the substance can do - irritation, dermatitis, sensitisation, long-term organ or respiratory effects - and the Workplace Exposure Limit where one exists. The HSE publishes WELs in the document EH40. For example, the WEL for respirable crystalline silica is 0.1 mg/m3 as an 8-hour time-weighted average, and for hardwood dust it is 3 mg/m3. Where a substance has a published WEL, a proper assessment states it.

Control measures, in the right order. COSHH requires control by a hierarchy, not by reaching for gloves first. The order is: eliminate the substance if you can; substitute a less hazardous one; apply engineering controls such as local exhaust ventilation, water suppression or on-tool extraction; then safe systems of work; and only then personal protective equipment as the last line of defence. A COSHH assessment that lists "wear gloves and a mask" as its primary control, with no consideration of whether the dust or vapour could be reduced at source, is one of the clearest signs of a substandard assessment.

PPE, storage, spillage and first aid. The specific protective equipment for this substance, how it is stored and handled, what to do if it is spilled, and the first aid response for each route of exposure. The spillage and emergency section is the second of the three commonly missing sections.

Health surveillance. Whether health surveillance is required, and what it involves. This is the third commonly missing section, and the one that most often catches people out. Where a substance can cause dermatitis or sensitisation - cement and many solvents among them - COSHH Regulation 11 requires health surveillance, typically skin checks at intervals, and the records must be kept for at least 40 years. Many otherwise decent assessments omit this entirely.

Risk rating and review. SSIP assessors increasingly expect to see a before-and-after risk rating - the risk with no controls, and the residual risk once the controls in the assessment are applied - along with a review date. A COSHH assessment should be reviewed at least annually, and immediately if the product changes, the task changes, or there is an incident.

The three sections where assessments fall down

If you take one practical point from this guide, make it this: the three sections most often missing from real COSHH assessments are routes of exposure, spillage and emergency procedures, and health surveillance. These are not coincidental omissions. They are the sections that a generic template tends to skip and that a busy person filling in a form tends to skim past, and they are precisely the ones an experienced assessor turns to first to gauge whether an assessment is real or for show.

Health surveillance is the most consequential of the three, because it is not just paperwork. If you regularly expose operatives to cement or solvents and you have no skin surveillance in place, you are not only failing an assessment - you are missing the mechanism that catches occupational dermatitis early, before it becomes a chronic, reportable, career-affecting condition. Dermatitis from cement is a known, preventable, and reportable industrial disease.

The substances most trades actually need to assess

There is no fixed number of COSHH assessments a business should hold - it depends entirely on the products you use. A typical construction or scaffolding firm commonly maintains anywhere from a few dozen to well over a hundred, because every product and formulation is different. The practical approach is to inventory every hazardous product you use, obtain the current safety data sheet for each, and assess it against the actual task.

Some of the substances that come up most often across the trades:

• Cement, mortar and concrete products. Alkaline and abrasive: they cause cement burns and contact dermatitis, and the hexavalent chromium content is a skin sensitiser. Mixing and cutting also generate dust. Cement work is a clear trigger for skin health surveillance.
• Respirable crystalline silica. Released when cutting, grinding or drilling concrete, stone, brick and block. The WEL is 0.1 mg/m3, and uncontrolled exposure causes silicosis and lung cancer. Water suppression or on-tool extraction is the expected control, not a dust mask alone.
• Wood dust. Especially hardwood and MDF dust, which can cause asthma and, with long exposure, nasal cancer. The hardwood WEL is 3 mg/m3, and on-tool extraction is the standard control.
• Solvents, adhesives and sealants. Vapour build-up in enclosed rooms, skin defatting and dermatitis, and in some products an aspiration hazard if swallowed. Two-pack and spray products may contain isocyanates, which are powerful asthma sensitisers needing particular care.
• Fuels, oils and degreasers. Petroleum-based products with skin, inhalation and environmental hazards, and often a flammability consideration.

For the broader picture of how COSHH fits alongside your other paperwork, our guide to the compliance documents every UK contractor needs sets out where COSHH sits among RAMS, your health and safety policy and the rest of the pack.

Where COSHH assessments go wrong

Beyond the missing sections, a handful of failures come up again and again. The first, already covered, is attaching the safety data sheet and calling it an assessment. The second is the generic copy-paste: an assessment that could describe any business using any product, with no task detail, no named controls, and no sense that anyone actually looked at how the work is done. The third is treating PPE as the answer to everything, in place of controlling exposure at source. The fourth is the out-of-date review: an assessment dated three years ago for a product the firm no longer uses, or a review date that passed long ago. Assessors check review dates as a quick proxy for whether the whole system is being maintained.

How Complys helps you write COSHH assessments properly

Complys generates task-specific COSHH assessments from your own details, and it is built specifically to avoid the failures above. You choose or enter the substance - any substance or branded product, not a fixed list - and describe how you actually use it: the task, the location, how often, who is exposed, and what controls you already have. Complys then writes a full assessment structured around every section a proper COSHH assessment needs, including the three that are most often missing: routes of exposure, spillage and emergency procedures, and health surveillance.

The part that makes the biggest difference to accuracy is the safety data sheet. If you upload the SDS for the product, Complys reads it directly and writes the assessment from the real hazard data - the actual CLP classification and hazard statements, the components, the exposure limits, the flash point, the first aid measures and the disposal requirements - rather than working from general guidance. That is the difference between a finished assessment and a draft you have to complete by hand. And since COSHH expects the safety data sheet to be kept alongside the assessment anyway, uploading it is simply good practice.

Each assessment applies the hierarchy of control properly, with PPE as the last line rather than the first, and includes a before-and-after risk rating and a review date set twelve months out. Your assessments live in a COSHH register where you can see at a glance which are in date and which are due for review - the review tracking that assessors check. And because the people doing the work need to be briefed on the substances they handle, Complys lets workers scan a QR code to read the assessment and sign that they have been briefed, building the record an inspector or assessor will ask for.

None of this removes your responsibility as the employer to check the assessment against the real conditions on your site and against the current safety data sheet. What it does is take you from a blank page or a generic template to a thorough, task-specific draft in a couple of minutes, structured to the standard COSHH requires.