Last updated:
Short answer: an aperture of about 1.0–1.4 mm keeps out house flies, wasps and most mosquitoes while letting air and light through. For tiny biting midges, go down to about 0.6 mm or less and accept less airflow. Use V2A stainless steel for normal sites and V4A on the coast. getwiremesh supplies the mesh flat, cut to your frame size, for fixed screens on windows, doors and vents.
Which aperture keeps which insects out?
The aperture is the clear opening between two wires. It decides what gets through:
| Aperture | Keeps out | Airflow |
|---|---|---|
| 1.2–1.4 mm | flies, wasps, moths, most mosquitoes | high |
| about 1.0 mm | also smaller mosquitoes and gnats | good |
| 0.5–0.6 mm | also biting midges | reduced |
Smaller openings always cost airflow and visibility. Start with the largest opening that stops the insects you actually have.
In the UK the driver is usually nuisance rather than disease: house flies and wasps in summer, mosquitoes near standing water, and biting midges in western Scotland and parts of the north. A 1.2–1.4 mm screen covers flies and wasps; only midge country needs the finer 0.6 mm mesh.
Why does the wire thickness matter?
A thinner wire leaves more open area, so more air and light pass through and the screen is harder to see. A thicker wire makes the mesh stiffer and more robust against pets, hail and cleaning. The open area in the table below is calculated from aperture and wire diameter, so you can compare meshes directly.
| Mesh | Aperture | Wire | Open area | Weight | Price |
|---|---|---|---|---|---|
| V2A 1.4 × 0.25 mm | 1.4 mm | 0.25 mm | 72 % | 0.6 kg/m² | £17.00/m² |
| V2A 1.25 × 0.4 mm | 1.25 mm | 0.4 mm | 57 % | 1.23 kg/m² | £25.00/m² |
| V4A 1.25 × 0.4 mm | 1.25 mm | 0.4 mm | 57 % | 1.23 kg/m² | £28.00/m² |
| V2A 1 × 0.3 mm | 1 mm | 0.3 mm | 59 % | 0.88 kg/m² | £22.00/m² |
| V2A 0.6 × 0.25 mm | 0.6 mm (600 µm) | 0.25 mm | 50 % | 1 kg/m² | £25.00/m² |
| V2A 0.5 × 0.2 mm | 0.5 mm (500 µm) | 0.2 mm | 51 % | 0.73 kg/m² | £22.00/m² |
Stainless steel or fibreglass?
Stainless steel lasts longer and stays taut. It does not sag, does not become brittle in sunlight and resists cat claws far better than fibreglass or plastic screens. The trade-off is that it is stiffer and heavier, so it needs a rigid frame. Choose V4A within reach of sea air; elsewhere V2A is sufficient. See V2A vs V4A for the details.
How do you fit a stainless steel insect screen?
Fit it in a rigid frame, under light, even tension:
- Measure the clear frame opening and add the overlap your frame profile needs.
- Order the sheet cut to that size; we cut every sheet to your width and length.
- Clamp or bead the mesh along one long side first, then tension towards the opposite side.
- Fold or cover the cut edges. Cut wire ends are sharp, so wear gloves.
For vents and air bricks, fix the mesh over the opening with stainless screws and washers so that no gap remains at the edge.
What insect screen mesh is not suited for
- Roll-up and pleated screens. These need a flexible fabric; stainless mesh would kink.
- Pollen protection. Pollen grains are far smaller than any insect screen opening and need a dedicated pollen fabric.
- Frameless fixing with tape or Velcro. The mesh is too stiff and heavy for adhesive fixing.
Frequently asked questions
What aperture keeps mosquitoes out?
An aperture of 1.0 mm or smaller stops the common mosquito species. Choose 0.5–0.6 mm where biting midges are the problem, and accept that airflow drops.
Does a stainless steel screen reduce airflow?
A 1.25 mm mesh with 0.4 mm wire leaves about 57 % of the surface open, so airflow drops only slightly. Fine midge mesh with a smaller open area reduces airflow noticeably and is best limited to windows that need it.
Can I cut stainless steel insect mesh myself?
Yes, with tin snips or a fine hacksaw, but the cut edge is sharp and can fray. Ordering the sheet cut to size avoids that and keeps the edge straight.
Which grade do I need for a coastal window?
Use V4A (AISI 316) within a few kilometres of the sea, where salt spray settles on the mesh. Inland, V2A (AISI 304) is sufficient.
Find all apertures in the V2A range and the V4A range. For protection against rodents rather than insects, see the guide to rodent-proof wire mesh.
Sources and further reading
- UK Health Security Agency: health protection guidance
- Wikipedia: mosquito nets and mosquitoes