The complete guide
Working out how much PVC flyscreen frame to order
Why it is sold by the metre
Windows are not standard. In an older house no two are the same, and a fixed kit is always either too big or too small for at least one of them.
Buying frame by the metre removes the problem. Measure the opening, work out the perimeter, add a margin for the cuts, and order that. Nothing is wasted on a length nobody needed.
The arithmetic is: twice the width plus twice the height. A 100 cm by 150 cm window comes to 5 metres. Order a little over, because everyone gets one cut wrong and running short halfway round a frame is a genuinely annoying way to lose an afternoon.
Flexible PVC rather than aluminium
The profile is flexible PVC. That choice does two things.
The first is that it cuts with a sharp blade or a strong pair of scissors. Aluminium framing needs a mitre saw and accurate 45 degree cuts, which is exactly the barrier that stops most people making their own screens. A flexible profile brings the job down to a tape measure and a knife.
The second is how it looks. A PVC frame is slimmer and lighter than an aluminium one, so a made-up screen sits discreetly on the window instead of announcing itself. It also copes with an opening that is not quite square, because it sits against the shape rather than fighting it.
What else the screen needs
Frame on its own does not make a screen. You also need corner pieces, mesh, and a fixing.
Corner pieces come in sets of four with two wind clips, and one set makes one screen. Mesh comes in three grades: standard grey, midge black for the small biting insects, and pet mesh for claws. The fixing is magnetic strip if you are building a magnetic screen, or hook-and-loop tape if you are building a velcro one. All of it is sold separately, on purpose, because the quantities do not scale together.
When building beats buying
For a single window, buy the made-up screen. It arrives ready, it is sized sensibly, and the saving from building is not worth the afternoon.
For four odd-sized windows, building is both cheaper and a better fit. You order the exact frame length the house needs rather than four kits sized for other people's windows, and every screen ends up matched to its opening.
Choosing the colour
Black, brown or white, all the same price per metre. Match the window surround rather than the wall: brown against timber, white against uPVC, black against dark or aluminium frames.
Get this right at the order stage. The frame sits at the edge of the glass in your eyeline every day, and painting flexible PVC afterwards is not a fix, because the paint does not stay on it.