Magnetic Fly Screens | DIY Insect Screens | Window Screens With Magnets

Nearly every window screen sold in a shop is made for a window that does not exist. Openings are rarely a standard size, and in an older British house no two match. This guide covers how to pick a screen that fits, which mesh to buy, and how to fit one without putting a hole in anything.

Start with the opening, not the product

Measure the frame recess rather than the glass. Every fixing here, magnetic strip or hook-and-loop tape, goes onto the flat face of the frame around the opening, so that face is what a screen has to reach and cover.

Then order the size above your measurement. Every screen in the range cuts down with a blade or a strong pair of scissors. Mesh will happily overlap a frame edge. It will not stretch to cover a gap, and a gap is precisely where insects get in.

What if nothing is square

That is the normal case in an older house, and it is where a flexible screen beats a rigid aluminium one. Because you cut each frame to the window in front of you, an opening that is a few millimetres out across its width stops being a problem. Rigid framing has to be measured, mitred and fitted to a tolerance. This does not.

Choosing between the two meshes

Mesh is the decision that matters most, and the one people get wrong by picking on price alone. There are three grades, and the right one depends on where you live and whether you have animals.

Standard grey, 18 x 16

Fibreglass woven 18 x 16 to the square inch, 66% open area, 0.279 mm strand. It stops flies, mosquitoes and wasps, and the open weave means you barely notice it from inside. For most houses away from water, this is the one to buy.

Midge black, a finer weave

The grade sold in the trade as no-see-ums screen. At a finer weave with 45% open area, the weave is tight enough to stop midges, gnats and sand flies as well as everything the standard mesh catches. Near water, marshland or the coast, ordinary fly screen lets the small biters straight through and this is what you want. The trade-off is a slightly darker view and a little less airflow.

You do not have to run one grade throughout the house. Midge mesh on the windows you open at dusk and standard grey everywhere else is a common split, and it keeps the cost down.

Standard mesh or midge mesh

This is the only choice that really matters, and it is about what is getting in rather than about the window. Standard mesh is 18 X 16 apertures per square inch. That stops flies, mosquitoes and wasps and still feels like an open window.

Midge mesh is the finer weave. If you are near water, or anywhere midges are the insect people actually complain about, a standard mesh will let them through and the finer one will not. It cuts a little more air, which is the trade you are making.

Everything else is the same between the two: same fixing, same three frame colours, same three sizes, same fitting time.

Measure the opening, then order the size above it

Measure the flat face of the frame around the opening rather than the glass, because the magnetic strip needs somewhere to sit. Then take the size above your measurement, never below it. The cutting only goes one way.

A 1m x 1m kit covers anything up to a metre square, the 1.5m x 1.5m up to a metre and a half, and the 2m x 2m up to two metres. What you trim off is waste rather than a compromise, and it is why one kit fits a range of windows instead of one exact size.

Why fibreglass rather than cheap nylon

The mesh is woven from glass yarn and coated in vinyl. It does not rust, corrode or stain, and it stays flexible instead of going brittle and splitting after a couple of summers, which is what finishes cheap nylon netting. It is also non-combustible, worth knowing about something that sits in a sunny window for months.

The practical test is simple. Flex a piece of old mesh between your fingers. If it cracks, it is done, and patching it only delays the job.

Building screens from parts

For one window, buy the made-up screen. For four odd-sized windows, buying the parts is both cheaper and a better fit.

PVC frame is sold by the metre, so you order the exact perimeter your windows need. Corner pieces come in sets of four with two wind clips, and one set makes one screen. Magnetic strip is sold by the metre as well, and a metre includes both mating strips. Replacement mesh comes in all three grades.

Work the frame out from the perimeter: twice the width plus twice the height, plus a little for the cuts. A 100 by 150 cm window comes to 5 metres. Order slightly over, because everyone gets one cut wrong.

Do not skip the wind clips

On a sheltered window you will never think about them. On an exposed one, wind pushes the middle of the screen away from the frame, and the moment it bows there is a gap down the side. Two clips hold it flat. Fit them at the build stage, because getting to them afterwards means taking the screen off the window.

Fitting, and the one mistake that matters

Wipe the frame face clean and let it dry before anything adhesive touches it. The adhesive gets exactly one attempt, and a dusty or damp frame is the most common reason a strip lifts a fortnight later.

Then press the strip down along its whole length rather than tacking the ends. A strip fixed at the ends looks fitted and is not, and it fails in the middle first.

Do each side as its own length rather than bending one continuous run around the corners. Easier to control, and the corners come out neater. The first window takes about twenty minutes while you work out the order of things. After that you will do one in five.

Living with them

Take a screen down and wash it in warm soapy water when it needs it, then let it dry fully before it goes back up. Keep grit off the face of a magnetic strip, because anything sitting on it holds the screen a fraction proud, and a fraction along a whole edge is a gap.

Some people leave them up all year. Others take them down in autumn and put them back in spring, which the magnetic fixing makes easy either way. Cat owners generally leave them up, and that is the sensible approach: the window gets used more, and there is never a week where the screen is in a cupboard and the window is open.

A short checklist before you order

Measure the frame recess, not the glass. Order the size above your opening. Pick midge mesh if you are near water and midge mesh if midges are the problem, otherwise standard grey. Choose midge mesh if midges are the problem where you live, otherwise standard. And if you are doing more than three windows, price up the parts before you buy the kits.