Can Bugs Get Through Mesh? Hole Sizes and What They Stop

Bugs can get through mesh only when the openings in the weave are bigger than the insect, so a standard 18×16 screen stops houseflies and most mosquitoes, while a tighter 20×20 or 24×24 weave also blocks beetles and sandflies.

That one sentence covers the physics, but it hides a lot of practical detail. Which weave do you actually need for a Singapore home? What about ants, cockroaches, and the house lizards that seem to appear out of nowhere? And why do some homes still get insects indoors every evening even after paying for mesh?

This guide goes through it bug by bug, with honest answers where mesh has limits. (If mosquitoes are your main worry, we've written a dedicated piece on whether mosquitoes can go through window mesh, including the dengue angle.)

How mesh stops insects in the first place

Insect mesh is a filter, nothing more. It's woven from strands of fibreglass, polyester, or stainless steel, and the specification that matters is the mesh count: how many strands per inch run in each direction. Standard fibreglass insect screening is around an 18×16 count, which leaves openings of roughly 1 mm. Air and light pass through without any trouble. A housefly, which is far larger than 1 mm, bounces off.

There's no chemistry involved and no repellent effect. The mesh doesn't kill anything or frighten anything away. It's purely a size game: if the insect's body is bigger than the opening, it stays outside. If it's smaller, the weave alone won't stop it, no matter what the packaging promises.

That's why mesh count is the first number to check. For Singapore, we recommend a weave of around 20×20 to 24×24: tight enough to stop the smaller biting insects (midges and sandflies, mostly), while still letting air move freely on a humid night. Every mesh MeshMates installs meets that standard, from budget fibreglass up to stainless steel. You can compare the materials side by side on our mesh types page.

One more thing worth saying early: the weave is only half the system. The other half is the seal around the edges, and that's where most "my mesh isn't working" stories actually come from. More on that below.

Which bugs can get through mesh? The Singapore lineup

Here's how the usual suspects in a Singapore home measure up against mesh. "Standard" means the common 18×16 weave; "tight" means the 20×20 to 24×24 range we recommend.

Two honest caveats hide inside that table, and we'd rather you hear them from us than discover them later.

First, ants. Singapore has some very small ant species, and the tiniest workers can squeeze through openings that would stop any flying insect. A weave fine enough to block them completely would also block most of your airflow, which defeats the point of having a window. Mesh will keep out the bigger ants and drastically cut down the traffic, but if a colony has found a food source in your kitchen, the fix is removing the food source and the trail, not a denser weave.

Second, crawling insects in general. Cockroaches, ants, and lizards don't fly into the middle of your window the way a mosquito does. They crawl along walls, pipes, and window frames, patiently probing for an opening. Against these intruders, the weave count is almost irrelevant: what matters is whether there's any gap at all around the edges of the mesh. A cockroach doesn't need to defeat your 24×24 weave when there's a 6 mm gap where the frame meets the grille.

Moths, for what it's worth, are the easy case. The ones that flutter around your lights at night are far too large for any insect mesh opening, so any properly sealed screen keeps them out.

The real weak point: gaps around the frame and grilles

If insects are getting in despite your mesh, the weave is almost never the culprit. The perimeter is.

Picture the finest mesh in the world installed with a 5 mm gap along one edge. To a mosquito, that gap is a motorway. Insects don't inspect your window and give up when the middle looks solid; they drift and crawl along surfaces until they find an opening, and a single one is enough. This is why density and sealing have to work together: a tight weave with a leaky perimeter protects nobody.

Window grilles are the usual offender in Singapore homes. Grilles create protrusions and uneven surfaces, and a mesh frame mounted carelessly over them leaves channels that insects follow straight indoors. Our installers deal with this daily: depending on your setup, the frame is positioned to avoid the grille entirely, or the gap is sealed so there's no path through. We've written up how this works for invisible grilles, casement grilles, and blinds in our window environment guide.

The install method matters here too. Our standard drill-free installation fixes the frame with specialised adhesive tape and silicone, which seals the perimeter as part of the process rather than leaving it to luck. No holes in your wall, which your landlord (or your HDB resale valuation) will appreciate.

Torn mesh is the other gap to watch. A small tear in a corner works exactly like an installation gap, so if your fibreglass mesh has been through a few years of sun and the odd pet encounter, check the corners and edges before blaming the weave.

Does a tighter weave kill airflow?

This is the worry we hear most often when we recommend 20×20 over standard 18×16, and the honest answer is no, not at any density you'd realistically buy for a window.

Moving from 18×16 to 20×20 or 24×24 shrinks the openings enough to stop midges, but the change in airflow is small enough that you won't notice it on an ordinary evening. Materials like polyester and fibreglass are woven from thin strands precisely so the open area stays high. Singapore homes live on cross-ventilation, and insect mesh is designed around that fact.

Where airflow genuinely drops is with dense fabrics that aren't insect mesh at all. Our sunshade and blackout options are made for heat and light control, and they block airflow by design. They're a different product for a different job, and we'll never suggest them as an insect solution.

So pick your weave for the insects you want to stop, not out of fear of stuffiness. The mesh isn't what makes a room feel warm; a closed window is.

Which MeshMates setup keeps bugs out

For insects, you don't need strength. A mosquito isn't going to shove its way through, so load bearing and scratch resistance barely matter. What you need is a fine weave, a gap-free install, and a frame you'll actually enjoy using.

The value pick is the Base with polyester mesh: highly transparent, strong airflow, and the retractable frame rolls away when you don't need it. Choose fibreglass instead if you'd like a slight privacy and sunshade effect thrown in; it's a touch less clear to look through, which some lower-floor homes count as a feature.

If you share the home with a cat, the calculation changes: lightweight insect mesh tears under claws, so you should buy for the cat and let the insect protection come free with the finer weave. The Core with stainless steel or pet mesh covers both jobs. Our guide to choosing window mesh walks through every specification and scenario if you want the full picture.

Whichever model you pick, the install is drill-free, takes under an hour for a typical window, and comes with a free site visit first so we can check your grilles and frames for the gap problems described above.

The bottom line

Bugs get through mesh in exactly two situations: the opening is bigger than the insect, or there's a gap around the frame. A 20×20 to 24×24 weave handles the first for everything from houseflies to sandflies. A properly sealed, gap-free installation handles the second. Sort out both and the only insects left in your flat are the ones that walked in through the front door.

Not sure what's getting in or how? Send us a photo of your window over WhatsApp. The site visit and quote are free, and we'll tell you honestly if your problem is the mesh, the gaps, or something mesh can't fix.

Frequently asked questions

Do bugs bite through mesh?

Mosquitoes can bite through mesh if your skin is pressed directly against it, since their mouthparts are longer than the mesh is thick. In practice this almost never matters: nobody sleeps with an arm against the window screen. Keep furniture a few centimetres off the mesh and biting through is a non-issue.

Can lizards get through window mesh?

Adult house geckos are far too large to pass through any insect weave, so a well-sealed mesh keeps them out. Hatchlings are another story: they're tiny and they crawl, so they exploit gaps around frames and grilles rather than the weave itself. If lizards are appearing indoors, check the perimeter of the mesh and other entry points like gaps under doors.

Why are insects still getting in when I have mesh installed?

Nine times out of ten, the answer is a gap: around the frame, at a grille, along a torn edge, or through a door that stands open while the windows are sealed. Inspect the mesh perimeter closely and check the corners for tears. If the mesh itself is intact, the insects are coming in somewhere else, and a free site visit can usually spot the entry point quickly.

What mesh size do I need to keep small insects out?

Standard 18×16 screening (openings around 1 mm) stops houseflies and most mosquitoes. To also block midges and sandflies, go tighter: 20×20 to 24×24 is the range we recommend for Singapore, and it keeps airflow strong. Anything dramatically denser trades away ventilation for little real gain.

Sources

Product and installation details are drawn from our own product pages, mesh types guide, and installation guides. External references:

1. Phifer: Standard fiberglass insect screening specifications, including the common 18×16 mesh count. phifer.com