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Construction compliance guide

COSHH Assessment for Builders: A Practical Guide

What COSHH means, which substances you need to worry about on site, and how to do an assessment without drowning in paperwork.

What is COSHH?

COSHH stands for the Control of Substances Hazardous to Health Regulations 2002. It is the law that requires every employer and self-employed person to assess and control exposure to hazardous substances at work, as detailed in the HSE’s COSHH guidance. It is not optional, it is not guidance, and it is not something that only applies to factories and chemical plants. If you work with substances that could damage your health — and in construction, you almost certainly do — COSHH applies to you.

A “hazardous substance” under COSHH is anything that can harm your health if you breathe it in, get it on your skin, swallow it, or get it into your body through a cut. That includes dust, fumes, vapours, gases, liquids, and biological agents. On a typical construction site, you will come into contact with several of these every single day.

The core duty is straightforward: you must assess the risks from hazardous substances on your site, put control measures in place to prevent or adequately control exposure, and make sure those controls are actually used. If you employ anyone, you must also provide information, instruction, and training on the substances they will be working with.

Common hazardous substances in construction

You do not need to be handling barrels of chemicals to have a COSHH obligation. These are the substances that builders encounter most often:

Cement

Wet cement is highly alkaline and causes chemical burns and contact dermatitis. Cement dust contains silica, which damages the lungs. Prolonged skin contact without protection can lead to serious, life-changing skin conditions. This is one of the most common causes of occupational ill health in construction.

Silica dust

Generated whenever you cut, grind, drill, or chase concrete, stone, brick, or mortar. Respirable crystalline silica is the leading cause of occupational lung disease in the UK construction industry. It causes silicosis, an irreversible scarring of the lungs, and is linked to lung cancer. There is no cure.

Solvents and adhesives

Paints, varnishes, lacquers, glues, and cleaning agents all release vapours that can be harmful if inhaled. Short-term effects include dizziness, headaches, and nausea. Long-term exposure can damage the liver, kidneys, and nervous system. Always check the label and the safety data sheet.

Wood dust

All wood dust is harmful to your lungs, but hardwood dust is classified as a carcinogen. Softwood dust can cause asthma. If you are cutting, sanding, or routing timber regularly, you need extraction or suitable respiratory protective equipment. The workplace exposure limit for hardwood dust is 3 mg/m³.

Isocyanates

Found in spray foam insulation, two-pack paints, and some adhesives. Isocyanates are one of the most common causes of occupational asthma. Even very low levels of exposure can sensitise your lungs, and once you are sensitised, any future exposure — however small — can trigger a severe asthma attack.

Asbestos

Technically covered by its own set of regulations (the Control of Asbestos Regulations 2012), but it overlaps significantly with COSHH. If you are working on any building constructed before 2000, you must consider whether asbestos-containing materials are present before you start disturbing anything.

How to do a COSHH assessment

A COSHH assessment does not need to be a 50-page document written by a consultant. For most builders, using the manufacturer’s safety data sheet and applying common-sense controls is sufficient. Follow these five steps:

1.Identify the substances

Walk through your project and list every substance that could be hazardous. Check labels, read safety data sheets, and think about what gets created during the work — cutting concrete creates silica dust even though you did not bring silica to site. Do not forget substances that are already in the building, like lead paint or asbestos.

2.Assess who might be exposed and how

Think about who comes into contact with each substance and how — inhalation, skin contact, or ingestion. Consider everyone on site, not just the person doing the task. Dust travels. Vapours spread. Someone working nearby can be exposed without touching the substance directly.

3.Decide on control measures

Follow the hierarchy of controls: eliminate the substance if you can, substitute it with something less harmful, enclose the process, use local exhaust ventilation, and only then rely on personal protective equipment. PPE is always the last resort, not the first. For example, use a wet-cutting method instead of dry-cutting concrete, and you drastically reduce silica dust at source.

4.Record and implement

Write down what you have found and what controls you are putting in place. If you employ five or more people, you must record it by law — but even if you are a sole trader, writing it down is good practice and shows the HSE you have done the work. Make sure the controls are actually used on site, not just written on paper.

5.Review regularly

Your assessment is not a one-off exercise. Review it whenever the work changes, new substances are introduced, or you have reason to think the controls are not working. At minimum, review annually. If someone reports skin irritation, breathing difficulties, or any other health symptoms, that is a clear signal to review your assessment immediately.

A quick note on Workplace Exposure Limits (WELs): these are the maximum concentrations of a substance allowed in the air, averaged over an 8-hour working day. You do not need a laboratory to comply — for most construction tasks, using the right controls (wet cutting, extraction, proper RPE) will keep you well within the limits. WELs are published in the HSE’s EH40 document, which is free to download.

How The Site Book tracks COSHH automatically

Researching every substance on every job is time-consuming, especially when you already know what the risks are and just need the paperwork to reflect it. That is where The Site Book comes in.

When you describe your project, The Site Book identifies substances likely to be present and flags COSHH considerations in your RAMS automatically. If you mention cutting concrete, it includes silica dust controls. If your project involves spray foam insulation, it flags isocyanate exposure. It includes control measures for common construction substances so you do not have to research each one from scratch.

The result is a set of RAMS that already accounts for the hazardous substances on your project — with the right control measures, PPE requirements, and safety precautions built in. You review it, adjust anything that needs changing, and download a professional document that covers your COSHH obligations as part of your wider site safety paperwork.

Frequently asked questions

Common questions builders ask about COSHH assessments.

Do sole traders need COSHH assessments?

Yes. The COSHH Regulations apply to every employer and every self-employed person. If you are a sole trader and you work with any substance that could harm your health — cement, silica dust, solvents, wood dust — you are legally required to carry out a COSHH assessment. The assessment does not need to be complicated. For most sole traders, reading the manufacturer’s safety data sheet, identifying the risks, and writing down the control measures you will use is sufficient. The HSE does not expect you to hire a consultant or set up a laboratory. They expect you to know what you are working with and take sensible precautions.

What’s the difference between COSHH and a risk assessment?

A general risk assessment covers all workplace hazards — working at height, manual handling, slips and trips, electrical safety, and so on. A COSHH assessment is specifically about substances that could damage your health through inhalation, skin contact, ingestion, or injection. Think of COSHH as a specialist subset of your overall risk assessment. In practice, many builders include COSHH considerations within their RAMS, which is perfectly acceptable as long as the substance-specific risks and control measures are clearly identified. The key difference is that COSHH requires you to think specifically about exposure routes, workplace exposure limits, and substance-specific controls like LEV (local exhaust ventilation) or specific types of RPE (respiratory protective equipment).

Do I need to monitor exposure levels?

Not always. The COSHH Regulations require exposure monitoring only where there is a risk of the workplace exposure limit (WEL) being exceeded, or where control measures might not be working properly. For most small-scale construction work — mixing a few bags of cement, cutting a handful of blocks with a wet saw — formal air monitoring is unlikely to be necessary. However, if you are doing prolonged or repetitive work that generates significant dust or vapour, such as dry-cutting concrete all day or spraying two-pack paints in a confined space, you should seriously consider whether monitoring is needed. When in doubt, use the hierarchy of controls: eliminate the substance, substitute it, enclose the process, or use extraction before relying on PPE alone.

Where do I find safety data sheets?

Every manufacturer and supplier is legally required to provide a safety data sheet (SDS) for any hazardous product they sell. You can usually find them on the manufacturer’s website by searching for the product name followed by “SDS” or “safety data sheet.” Your builders’ merchant should also be able to provide them on request. The SDS contains 16 sections covering everything from hazard identification and first aid measures to exposure controls and PPE recommendations. The sections most useful for your COSHH assessment are Section 2 (hazards identification), Section 7 (handling and storage), and Section 8 (exposure controls and personal protection). Keep copies of the safety data sheets for every hazardous product you use on site — they form the foundation of your COSHH assessment.

What PPE is required for cement work?

Wet cement is alkaline and can cause serious chemical burns and cement dermatitis. At a minimum, you should wear waterproof gloves (not standard rigger gloves — cement eats through them), long sleeves, full-length trousers, and waterproof boots when working with wet cement or concrete. Eye protection is needed if there is any risk of splashing. For mixing cement or cutting concrete blocks, you also need respiratory protection — an FFP3 mask or powered respirator depending on the dust levels — because cement dust contains silica. Barrier cream is not a substitute for gloves, but it can help as an additional layer of protection. If cement gets on your skin, wash it off immediately with clean water. Do not wait until your break.

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