If a screen is fitted, fits correctly, and the bites carry on, the usual explanation is not a fault. It is that the insect is smaller than the aperture. Sand flies pass through standard mesh, and only a finer weave stops them.
01RULE OUT GAPS FIRST
Run your palm along the edge of the closed screen. If you feel a draught, the gap is closed first and only then is the weave worth discussing.
02THE TELL IS SIMPLE: MOSQUITOES GONE, MIDGES STILL THERE
The screen is working at mosquito size and failing at sandfly size. That is the aperture, not the mechanism.
03THE MESH IS CHANGED WITHOUT CHANGING THE FRAME
The fitter takes the screen down, pulls the old mesh out of the groove and fits a finer one into the same frame. That costs less than a new screen.
04WHAT NOT TO DO
- Fit two screens one behind the other: the air stops passing
- Tape up the perimeter: temporary, and it ruins the frame
- Take the finest available mesh 'just in case' in a dusty area
- Change the mechanism when the aperture is at fault
How to know it is them
The bites are smaller and there are more of them, often several in a cluster.
You do not hear the whine: sand flies fly silently, unlike mosquitoes.
They are most active at dusk and at night.
And the main clue: the screen is in place, undamaged, correctly fitted, and it changes nothing.
Why standard mesh does not help
Ordinary mesh is designed for mosquitoes and flies. Its aperture is larger than a sand fly's body.
From outside a screen looks identical whatever the weave. The difference is only visible up close, and that is why the problem is usually diagnosed after the purchase rather than before.
The frame and the mechanism are not to blame here, and replacing the whole screen is unnecessary.
What actually works
A finer weave. It is fitted into the same frame, and if the frame is straight only the fabric is changed.
What comes with it: a finer mesh passes slightly less air and is a little more visible against the light. That is the honest trade-off, and it is worth knowing before ordering rather than after.
It clogs with dust faster too, because the aperture is smaller. It needs cleaning more often.
Where it matters most
Near water: canals, lagoons, marinas, coastal districts.
In landscaped districts with daily irrigation.
On lower floors and in villas, where the insect comes from ground level.
Up in a tower the problem is rarer, but the airflow carries them high on occasion.
If a screen is fitted, fits correctly and the bites carry on, it is usually not a fault — the insect is simply smaller than the aperture.
What to do next
If a screen is in place and the bites continue, do not order a new construction straight away.
Send a photograph of the mesh close up: often the weave can be identified from it.
If the frame is sound, the technician changes only the fabric, which is cheaper and quicker than a new screen.
If the frame is bent or the mechanism is worn, we say so and quote both jobs separately rather than bundling them.
