What is hail and how does it form?
The German Weather Service (DWD) defines hail as precipitation in the form of balls or lumps of ice. Ice particles with a diameter of five millimetres or more are classed as hail. Smaller ice particles are known as graupel. Hailstones are generally between five and 50 millimetres in diameter, but can become considerably larger during particularly severe thunderstorms.
Hail forms in tall thunderclouds. Supercooled water droplets attach themselves to small ice particles and freeze. Powerful updraughts repeatedly carry the developing hailstones upwards within the cloud. More water droplets can then accumulate and freeze into new layers of ice.
What damage does hail cause and how can it be identified?
The German Weather Service (DWD) defines hail as precipitation in the form of balls or lumps of ice. Ice particles with a diameter of five millimetres or more are classed as hail. Smaller ice particles are known as graupel. Hailstones are generally between five and 50 millimetres in diameter, but can become considerably larger during particularly severe thunderstorms.
Hail forms in tall thunderclouds. Supercooled water droplets attach themselves to small ice particles and freeze. Powerful updraughts repeatedly carry the developing hailstones upwards within the cloud. More water droplets can then accumulate and freeze into new layers of ice.
Hail primarily affects external components of the building envelope, such as roof tiles, roof membranes and rooflights. If indentations, cracks or perforations occur, water can quickly penetrate and damage the thermal insulation, roof structure and interior.
Rooflights are also at risk because of their exposed position. Damage may affect not only the glazing, but also frames, fixings, seals, upstands and opening elements. The quality and resilience of the skylights are particularly important here.
Typical signs of hail damage include:
- Cracks, fractures or spalling
- Dents and noticeable deformation
- Lightened areas or changes in the plastic
- Damaged frames, profiles or fixings
- Displaced or loose seals
- Moisture or water stains inside the building
- Problems when opening and closing
- Faults in ventilation or SHEV components
How much can hail damage cost?
Hail primarily affects external components of the building envelope, such as roof tiles, roof membranes and rooflights. If indentations, cracks or perforations occur, water can quickly penetrate and damage the thermal insulation, roof structure and interior.
Rooflights are also at risk because of their exposed position. Damage may affect not only the glazing, but also frames, fixings, seals, upstands and opening elements. The quality and resilience of the skylights are particularly important here.
Typical signs of hail damage include:
- Cracks, fractures or spalling
- Dents and noticeable deformation
- Lightened areas or changes in the plastic
- Damaged frames, profiles or fixings
- Displaced or loose seals
- Moisture or water stains inside the building
- Problems when opening and closing
- Faults in ventilation or SHEV components
The roof should therefore be inspected promptly after a severe hailstorm, as not all damage is immediately visible. Fine cracks in the glazing or damaged seals may initially go unnoticed, but can later lead to leaks and costly consequential damage. Early refurbishment helps limit replacement to individual components and prevents more extensive damage to the building and business operations.
What should you do after hail damage to the roof?
After a severe hailstorm, visible damage should first be checked and documented from a safe distance. Photographs of the affected areas, together with details of the time, moisture and any functional faults, will make the subsequent assessment easier. The roof must not be accessed without appropriate safety measures. Rooflight domes, continuous rooflights and other translucent roof areas may present a fall-through hazard in particular. A detailed inspection should therefore be left to qualified specialists.
Refurbishment after storm and hail damage with LAMILUX
Hail damage to rooflights can quickly result in costs in the five- to six-figure range. The damaged skylights themselves are often not the only issue. If moisture enters the building through cracks, damaged seals or leaking connections after a hailstorm, it can also damage machinery, stock, furnishings or the roof structure. Replacing several rooflights alone can cost tens of thousands of euros.
Damage | Typical cost |
| One damaged rooflight dome | approx. EUR 1,000 to 3,000 |
| Several rooflight domes in an industrial building | approx. EUR 10,000 to 50,000 |
| Damaged continuous rooflight | approx. EUR 5,000 to 30,000 |
| Several continuous rooflights incl. SHEV components | approx. EUR 30,000 to 100,000+ |
| Hail damage with consequential damage inside the building | well over EUR 100,000 |
Refurbishment also provides an opportunity to upgrade the existing system technically and in terms of energy performance, for example with regard to thermal insulation, daylight incidence, natural ventilation or smoke and heat exhaust ventilation. LAMILUX supports the entire process, from the condition survey and planning through to manufacture and professional installation. A damage hotline is also available for acute storm, hail and roof damage.
Hail resistance: how to reduce future damage
To make the hail resistance of components comparable, they are tested under defined conditions. Ice balls with a specified diameter and corresponding velocity strike defined points on the component.
There are five hail resistance classes:
Tested systems and regular inspections
For new-build and refurbishment projects, attention should therefore be paid to the verified hail resistance of the complete skylight. Selected LAMILUX solutions, including the LAMILUX Rooflight Dome F100 W, LAMILUX Continuous Rooflight B, LAMILUX Flat Roof Window FE and LAMILUX Glass Roof PR60, are rated for resistance to hailstones up to five centimetres in diameter. The specific product configuration is always decisive.
Regular inspections and professional maintenance also help protect roofs and rooflights against hail. Existing systems should be checked for cracks, material changes, damaged seals and functional faults. Weather exposure and material ageing can affect the resilience of older components in particular.
An additional visual and functional inspection is therefore recommended after a severe hailstorm. This allows minor hail damage to be identified early, before leaks or more extensive consequential damage develop.
