Gutters (when fitted) are one of the most susceptible parts of a building to damage from ash fall. They can accumulate ash from the roof (acting as an ash trap) and can easily pull apart or collapse from a roof, especially if the ash is wet and thus heavier. Gutters clogged with ash can also reduce the drainage capacity and further increase roof loading. It is recommended to clean gutters as soon as it is practical and safe, to avoid blockage and corrosion damage.
Downspouts and drains attached to gutters may also become clogged with ash, especially if it rains during or after ashfall, or if water is used to remove ash from a roof. It is recommended to disconnect downpipes following an ashfall. Ash blocked blocked gutters and downpipes can lead 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.
If a building's downspouts and drains connect to a wastewater network, effort should be made to disconnect or block a building's roof drains before or immediately after an ash fall to prevent ash from entering the drains and waste-water systems.
Gutters, drains and other non-structural elements of a building can be damaged or disrupted by much less ash (as little as several millimetres) compared to the much higher thicknesses (loads) required to cause structural damage.