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 South African 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 three 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, 20 x 20

The grade sold in the trade as no-see-ums screen. At 20 x 20 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.

Pet mesh, 10 x 16

Woven from heavy-duty vinyl-coated polyester yarn rather than fibreglass, which is where the strength comes from. A cat goes through an ordinary insect screen in a few days. This does not tear under claws, and it still gives a clear view out because the yarn is dark.

You do not have to run one grade throughout the house. Pet mesh on the two windows the cat actually uses and standard grey everywhere else is a common split, and it keeps the cost down.

Magnetic or velcro

Both fix without drilling and both come off cleanly. The difference is how you open the window.

A magnetic screen sits on a slim PVC frame held by a magnetic strip stuck around the window. There are finger tabs on the bottom corners. Pull one, the corner lifts, you open the window, and letting go brings the screen back. That takes a second.

A velcro screen is a flexible edged panel that presses onto hook-and-loop tape. It is the cheaper option and it seals just as well, but opening the window means peeling an edge back and pressing it down again afterwards.

The honest rule: on a window you open every day, the magnetic screen earns the extra. On a bedroom window you crack open in July, the velcro screen does the same job for less.

Screen doors work differently

A door screen has a different problem to solve. A door you have to unlatch gets propped open by the second week of summer, and a propped door is not doing anything at all.

The magnetic screen door solves it by closing itself. Up to 40 magnets are sewn into the fabric down the full height of the centre seam, so the two halves pull together from top to bottom as you walk through. Budget door screens use 26 or fewer, spaced out, which shuts the middle and leaves the top and bottom gaping just enough for flies.

It fits with a velcro strip stitched to the screen that presses onto the door frame. When you measure, allow 2 cm at the top and 2 cm on each side for that strip. People miss this and order a size short.

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 pet mesh if you have a cat, otherwise standard grey. Choose magnetic if you open that window daily and velcro if you do not. On a door, add 2 cm top and 2 cm each side. And if you are doing more than three windows, price up the parts before you buy the kits.