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What is Category 1 hazard?

Last verified 23 October 2026

A Category 1 hazard is a serious hazard in a home that scores 1,000 or more under the Housing Health and Safety Rating System (HHSRS). When a council in England finds one, it must take enforcement action.

Why it matters to landlords

The duty is what sets Category 1 apart. For lower scoring Category 2 hazards a council can choose whether to act, but for Category 1 it must choose a course of action, such as an improvement notice, a prohibition order, emergency remedial action where there is an imminent risk of serious harm, or in extreme cases a demolition order. Councils can also impose a civil penalty for Category 1 hazards in some cases.

Any HHSRS hazard can reach Category 1 if the risk is high enough. Government guidance says homes must not contain Category 1 hazards, and that the system covers mould and all types of dampness. Excess cold, falls, fire and electrical hazards are other common examples. Finding and fixing these before a tenant complains protects the occupier and avoids enforcement.

Example

An inspector finds a flat with no working heating and badly fitting windows and scores excess cold above 1,000. Because it is a Category 1 hazard, the council must act, so it serves an improvement notice requiring a working heating system.

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