Damage to buildings and building support systems from volcanic ash can range from minor cosmetic damage to building exteriors through to catastrophic structural damage in extreme cases. The level of impact will be dependent on the amount and characteristics of the ashfall, the design and quality of the building and building support system and the environmental conditions at the time of and after ashfall.

Damage to buildings may be significantly reduced by taking several key steps before, during, and after ashfall.

Summary of Ash Impacts to Buildings and Building Support Systems

  • Building interiors: Ash contamination of building interiors may lead to: risk of health hazards for building occupants (see; damage to sensitive equipment; abrasion damage to flooring.
  • Abrasive damage to roofing, cladding and floor materials during ash removal
  • Loss of essential services to building, due to disruption by ashfall
  • Building Support Systems: systems which allow building to function
    • Heating, air-conditioning and ventilation (HVAC) systems are vulnerable to disruption due to obstructed filters, condensers & air intakes
  • Building Envelope: non-structural elements
    • Gutters (when fitted) can accumulate ash from the roof, reducing the drainage capacity and further increasing loading. Ash may block gutters and downpipes, leading to localised flooding and damage, especially on roofs, drainage networks, and in ceiling spaces. Internal gutters are particularly at risk and are not easily accessible for cleaning.
    • Metal roofs, fastenings and claddings may be vulnerable to corrosion when exposed to ash.
    • Recently applied paint may also be vulnerable to ash leachate damage
  • Structural damage due to excessive ash loading. Very thick ash deposits (>100 mm, more commonly >300 mm) may cause roof collapse, although this ash thickness is rare.
    • Long span, low pitched roofs are typically the most vulnerable
    • When ash is wet, static loads may increase by up to 100%

The overall level of impact will be dependent on all these elements, as buildings act as an interdependent system. Mitigation measures can reduce and in some cases avoid impacts with rapid and regular removal of ash (when it is safe to do so).

However, clean up of building exteriors and interiors can be expensive, time-consuming and may need to be on-going (on-going ashfall or remobilisation of ash by wind and water)

Damage to buildings may be significantly reduced by taking several key steps before, during, and after ashfall .

Building Clean Up

Visit the Building Clean-Up section of this website for complete information about procedures to remove ash.


Roof tops may be slippery or at the limit of their load capacity! Be extremely careful when working on a roof, even on roofs with low to moderate pitch, and especially when covered with slippery material. Use personal protective measures when removing ash from roofs. Use a strong ladder, safety harness, filter facemask, gloves, and eye goggles.

For safety and prevention of unnecessary damage to roof material and surfaces, use protective measures during cleanup. For example, use planking, mats, plywood sheets, and pliable footwear to prevent slippage and damage from impact and abrasion; when using shovels, rakes, or other tools, be careful of the underlying roof surface; the full force of water from fire hoses can easily break lap shingles or tear lap roofing material.

See Also:
Remobilisation & Coping With Long-Term Ash
Cleanup, Disposal & Reuse > Buildings & Households