Cluster flies gather in large numbers in lofts and roof voids to overwinter, often in properties on the edge of farmland across Cheshire and Lancashire. They are sluggish, they cluster at windows on mild days, and they can return to the same building year after year.
Signs of cluster flies
- Large numbers of slow flies at loft windows
- Piles of dead flies in loft spaces
- Sudden indoor activity on mild winter days
Health risks
- Not a significant health risk, but numbers can be substantial and unpleasant
Property damage
- Staining on window frames and sills from fly deposits
What you can do yourself
- Household sprays deal with the visible flies only
- Numbers rebuild as more enter through the same gaps
When to call a professional
- Loft space treatment where appropriate
- Advice on proofing gaps at the roofline
- Guidance on timing, since prevention works best before autumn
Prevention tips
- Seal gaps around soffits, tiles and loft windows
- Address entry points during summer, before flies arrive
Frequently asked questions
Why does it happen every year?
The building itself is attractive as an overwintering site, so proofing matters as much as treatment.
Dealing with cluster flies right now?
We cover Merseyside, Cheshire, Greater Manchester and Lancashire. Send your postcode and we will confirm the earliest appointment.
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