Flies Hibernating in the loft ( Cluster Flies )

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Cluster Flies Hibernating in the loft

Flies hibernating in the loft can cause distress when they appear in the house during autumn and winter. Treatment is often simple and inexpensive.  One treatment is normally sufficient. This may require re – treatment each year.

Most flies seek refuge in lofts, barns and other cool spaces to survive through the winter. For some house owners this is the beginning of a fly problem, as hundreds, often thousands of flies choose their loft space as a winter refuge. As the house temperatures rise and fall throughout the day and night, the flies become active, then dormant again. During active periods they often fall into the rooms below, through loft hatches and light fittings.

Treatments to eradicate this problem are very simple. Usually a fog treatment is used to fill the loft space. This is very safe and leaves no residue. It is safe to re-enter a loft two hours after treatment. During the treatment the flies become very active, and the chemical fog kills them. Hibernating flies in the loft are best controlled in late autumn, once the cold weather is here for good.

Open or vaulted ceilings

Large houses with open roof systems, sometimes referred to as a vaulted ceiling, can be more difficult to deal with. With no enclosed loft, access to the hibernating flies can be restricted. However, the fog can be safely placed in a closed room, and allowed to permeate through cracks and crevices in the ceiling.


Treatments for hibernating flies in lofts can not be carried out where bats are present. A visual inspection is required prior to treatment, and where bats are seen no work will be carried out.