The assessment process is not just a question of spotting defects, but is all about risk assessment, outcomes and effects. When an inspector finds a hazard, two key tests are applied:

1. What is the likelihood of a dangerous occurrence as a result of this hazard

2. If there is such an occurrence, what would be the likely outcome?

For example, a staircase that had a broken stair would represent a serious hazard in that an occupant could trip or fall down the stairs. However a broken stair at the top of the staircase would obviously be more dangerous than one at the bottom. If, for example, a glass door was situated near the bottom of the staircase, that would increase the potential severity of the outcome even more.

Dwellings are assessed against the average for the type and age of building. The inspector also judges whether the condition increases or lowers the likelihood of an occurrence. The system provides information about the characteristics of average dwellings, as a basis for inspectors' own assessments of the conditions they find.

Inspectors will normally concentrate on hazards that are likely to be worse than the average, but they will be able to assess any of the 29 hazards on the basis of their observations or their knowledge of hazards that are specific to particular areas, such as radon. Where a hazard is designated as particularly relevant to people in a vulnerable group, hazards are assessed according to their likely impact on that group. 'Vulnerable' here usually means children and the elderly. For example, widely spaced spindles on a staircase could be a hazard for a child who could squeeze through and fall down the stairs. Similarly a winding staircase with no handrail could be a hazard for an elderly person.

The action that needs to be taken to deal with a hazard will be influenced by who is occupying the property (see How will the system be used in practice?) Once a property has been made safe for the most vulnerable, it should be safe for all.