Hail events are often characterised by their immediate visual impact on the exterior of a property, but the most significant risks frequently remain hidden from view. Hail is capable of puncturing tiny openings in roofing materials, which allows water to creep into ceiling voids and wall spaces. Even minimal holes can permit moisture to run along internal framing for a significant period before any visible marks appear on the interior linings. Because water can travel far from the initial entry point, staining on plasterboard often does not line up with the actual roof damage. Timely and accurate professional assessments are essential to identify these pathways and prevent secondary issues like mould growth.

Water Behaviour and the Role of Insulation

The way water moves through a ceiling cavity is determined largely by the materials it encounters. Water entering through hail-related damage may migrate along trusses, battens, or service penetrations before dripping onto the surfaces below. Metal roofing components, such as steel battens and top hats, are particularly problematic because their profiles can act as gutters that direct water far away from the original point of entry. Additionally, if hail or ice blocks external gutters, water can back up in valleys and overflow directly into eaves, wall cavities, and ceiling voids.

The presence of insulation significantly changes the risk profile of a moisture event:

• Ceiling Cavities Without Insulation: In unoccupied spaces between the ceiling and roof where no insulation is present, high temperatures generally allow small amounts of moisture to evaporate quickly before mould growth or staining occurs.
• Ceiling Cavities With Insulation: Wetted insulation is a concern because it retains moisture for long periods. This sustained dampness can allow mould to develop on the top side of the plasterboard before the material has a chance to dry naturally.
• Performance Loss: Any insulation that becomes wet must be replaced because it loses its thermal performance.

Managing Water Intrusion in Wall Cavities

Wall cavities are hidden spaces that can trap significant amounts of water. Ingress into these areas is often restricted by structural elements such as top plates, door and window frames, or noggins. While minor entry may be stopped by these horizontal barriers, significant water can travel down to the bottom plate at the base of the wall. Staining or swelling at the base of a wall may not become apparent for several days after the initial storm.

To ensure a defensible and effective drying outcome when significant water reaches the base of a wall, RIC Solutions follows established best practices:

• The skirting board at the base of the affected wall should be removed.
• A small inspection or drying opening should be created in the plasterboard to allow the internal cavity to ventilate.
• Any internal insulation that has become wet must be removed to prevent it from promoting mould growth.
• Early drying intervention, including structural drying, is the most effective way to reduce the likelihood of mould.

The Role of Technology in Assessments

Trained professionals utilise a range of non-invasive techniques to inspect hidden wall spaces and interstitial areas. Thermal imaging cameras are the most effective non-invasive tools for identifying potential moisture immediately following a hail or storm event. These cameras detect temperature variances caused by evaporative cooling, which can indicate moisture-affected materials or hidden wet insulation.

However, technology must be paired with expertise. Untrained operators may misinterpret thermal differences caused by missing or incorrectly installed insulation as moisture, leading to a false determination of wet materials. All thermal anomalies must be confirmed through moisture meters, physical inspection, or cavity access.

Summary of Findings for Stakeholders

Experience in the restoration industry shows that extensive removal of wall and ceiling linings due to hail damage is very rare. Most minor water intrusion into voids and cavities will dry without causing permanent damage or mould growth.

It is important to remember that while mould growth can start to form within 48 to 72 hours of excess moisture, it is generally only visible after five to eight days. Furthermore, plasterboard that has been wet or stained but remains structurally sound generally does not require removal. Finally, always be aware of potential electrical hazards when dealing with wet walls and ceilings where electrical systems are present.