How to Get Rid of Cluster Flies in the Home

Swat a cluster fly on the window sill and another seems to appear within the hour. If that sounds familiar, the flies you can see are only a small part of the problem.

Most of them are coming out of a hidden roost, usually the loft or a wall void. Getting rid of them properly means dealing with that source, not just the stragglers.

Start with the flies you can see

For the ones in your rooms, the simplest tool is the vacuum cleaner. Use a hose attachment on window sills, curtain tops and ceiling corners, then empty the bag or bin outside straight away.

Cluster flies are slow and rarely fly off, so you can also scoop them up with a piece of card and a cup and put them outside. It is tedious, but it causes no mess and no risk for children or pets.

Why shop-bought sprays rarely solve it

Fly sprays and plug-in devices may knock down the flies that happen to be in the room, but they do not reach the large group tucked into the roof space or behind fascias. More emerge the next sunny day.

Sprays also need care around food, children and pets, and flies killed in hard-to-reach spots simply add to the dead insects that can build up. Always follow the label on anything you buy, and keep it away from where food is prepared.

Look for how they are getting in

If you can safely see the loft hatch from below, look for flies near it. Do not go crawling around on the joists if you are not confident about it, as an unboarded loft floor is easy to fall through.

From outside, check for places a fly could slip in. Sealing such gaps can reduce new arrivals over time, though cluster flies can squeeze through very small openings, so proofing alone seldom ends an established problem.

• Cracked or missing mortar and pointing
• Gaps around soffits, fascias and roof edges
• Holes around pipes or cables
• Ill-fitting window frames and trims

What professional loft fumigation involves

For persistent cases, a professional treats the roof space itself, where the flies settle. A technician will inspect first to see where the flies are gathering and whether the loft is accessible and safe to treat.

Treatment is planned around the property and the time of year, and it is not something to improvise at home. Essex Pest Solutions offers cluster fly loft fumigation for homes and other buildings across Essex, and the details depend entirely on what an inspection finds.

Clear up afterwards

Once the flies are gone, vacuum up the dead ones from sills and loft access areas, because leftover insect remains can attract other pests. Wear a dust mask if you are clearing a dusty loft.

Then keep an eye on the following autumn. Cluster flies often return to the same building, so early action tends to be easier than waiting for the loft to fill again.

Frequently asked questions