How to Replace a Damaged Fly Screen Without Buying a New Frame

By Mick — lead handyman, Newcastle NSW.

I was at a quote in Merewether last summer — lovely art-deco place, lady of the house had been told by a “window guy” that her four damaged fly screens needed replacing at $89 each. That’s $356 for what is genuinely a 20-minute job per screen with $30 of materials. The frames were aluminium, perfectly straight, no corrosion. They just needed re-meshing. I did them while she made me a coffee.

This is one of those repairs where the marketing has run away from reality. Bunnings sells a spline tool for $8.50, a roll of charcoal mesh for about $25, and that gets you four to six screens depending on size. Most blogs tell you to chuck the frame because that’s what the YouTube algorithm rewards — replacement content gets more clicks than repair content. The frame is fine. It’s the mesh and the spline that fail.

The other thing nobody mentions: standard fibreglass mesh is rubbish in Australian sun. Two summers of UV on a north-facing window in Newcastle and it’s brittle enough to poke a finger through. I’ll tell you what to use instead so you’re not back doing this every two years.

Worth noting before we start: this is the lowest-stakes home repair you can do. If you stuff up the first attempt, the worst case is you’ve used a metre of $5/m mesh and you start over. Compared to drilling holes in tiles or adjusting cabinet hinges, fly screens are forgiving. Good first DIY project for someone who hasn’t done much around the house. The skills transfer too — once you’ve splined a screen, you’ve learned tensioning, edge-trimming with a Stanley knife, and reading what “drum-tight” feels like, which all come up in upholstery, vinyl wrapping, and a dozen other repair jobs.

What you’ll need

• Spline roller tool (the little wheel on a handle — Bunnings $8.50, the Cyclone-branded one is fine)
• New spline cord — measure your old spline diameter first, usually 4 mm or 4.5 mm
• Charcoal-coloured polyester or aluminium mesh — NOT fibreglass for anywhere that gets afternoon sun
• Stanley utility knife with fresh blade (worn blades tear mesh and leave fluff)
• Flat-head screwdriver for prying out the old spline
• Scissors
• Bricks or heavy books (4 of them) to weigh the frame flat
• A clear bench or kitchen table you can work on without scratching

Step 1: Pop the screen out of the window or door

Most Aussie sliding fly screens lift up and out — push up firmly, swing the bottom out, and lower. Fixed screens usually have small clips or screws at the top edge. Don’t lever from the mesh side or you’ll bend the frame. Lay the frame flat on your bench, mesh-side up.

Step 2: Identify the spline channel and the spline diameter

Look at the inside edge of the frame — there’s a groove (the spline channel) that holds a round rubber cord (the spline) which traps the mesh. Use the flathead screwdriver to lift one corner of the old spline up. Once you’ve got an end, pull steadily — it usually comes out in one piece. Measure the cord’s diameter with a vernier or just take the offcut to Bunnings to match. 4 mm and 4.5 mm look almost identical and the wrong one either won’t grip the mesh or won’t sit in the channel.

Step 3: Pull the old mesh off and clean the channel

The mesh lifts straight off once the spline’s out. Vacuum or wipe the channel — old fly bodies, dust, and bits of perished spline accumulate in there and stop the new spline seating properly. A toothbrush is good for this.

Step 4: Choose the right mesh

This is the Aussie gotcha: standard fibreglass mesh is the cheapest option at Bunnings and the most-recommended on US blogs because their UV is gentler. In Australia — especially anywhere from Newcastle north — fibreglass goes brittle in two summers on west or north exposure. Use either:

• Charcoal polyester mesh — UV-stabilised, lasts 7–10 years in Aussie sun, dark colour means you see through it better than the grey fibreglass
• Aluminium mesh — basically lifetime, bit harder to work with because it doesn’t stretch, but the right choice for coastal homes

Don’t bother with stainless unless you’ve got a security need — it’s three times the price and fingers-crossed-overkill for fly exclusion.

Step 5: Cut the mesh oversized

Roll the mesh out across the frame and cut it 50 mm bigger than the frame on every side. You’ll trim the excess later. Lay it flat with the weave running square to the frame — if it’s running on a diagonal you’ll get a lumpy finish.

Step 6: Start splining at one corner

Put the mesh in position. Take your new spline and push 30 mm of it into one corner of the channel by hand. Now use the convex (rounded) end of the spline roller to roll the spline down the long edge of the frame, pressing the mesh into the channel as you go. Keep moderate downward pressure — too hard and you’ll push mesh through and out the bottom; too soft and it won’t seat.

Step 7: Tension the mesh as you go

This is the technique bit. After the first long edge is splined, gently pull the mesh taut across to the opposite long edge before you spline that side — but don’t yank it. Mesh should be drum-tight, not stretched-thin. Aluminium mesh doesn’t stretch at all so you just need it flat. Polyester will stretch a touch and that’s okay — drum-tight is the goal.

Step 8: Do the short ends last

Once both long edges are splined, do the short ends. Don’t try to pull the mesh in two directions at once — you’ll get diagonal puckers. Spline the short ends, working from the centre out to the corners.

Step 9: Trim the excess mesh

Stanley knife, fresh blade, blade angled slightly outward so it slides along the OUTSIDE edge of the spline (not the inside). One smooth cut per side. Don’t saw at it — sawing leaves whiskers. If you nick the spline while trimming, it’s fine, the spline isn’t structural.

Step 10: Reinstall and test

Pop the screen back in the window. Push gently against the mesh from outside — a properly tensioned screen feels like a snare drum. If you’ve got a soft spot where the mesh isn’t fully seated, the spline roller can usually fix it by rolling that section again. If the spline pops up out of the channel, the spline diameter is too small — pull it out and grade up to the next size.

Common things that go wrong

The mistakes I see most often when people are doing this for the first time:

• Diagonal puckers across the screen. You tensioned in two directions at once. The fix is to lift one short edge’s spline back out, re-tension across that axis, and re-spline. The mesh weave needs to run square to the frame or no amount of pulling fixes the look.
• Spline keeps popping out of the channel. Wrong diameter — it’s too small. Take the spline to Bunnings, lay it next to the next-size-up roll and compare. Most frames are 4 mm or 4.5 mm but a few European-spec frames use 5 mm.
• Mesh tears at the corner during splining. You went too hard with the spline roller into the corner. The trick is to ease pressure as you approach the corner, push the spline into the corner with your fingertip, then start rolling again from the new edge.
• New mesh sags within 6 months. Polyester mesh that sags has usually been over-stretched during installation — it’s plastic deformation, not seasonal movement. Drum-tight, not stretched-thin. If you can’t fix the sag by re-tensioning one edge, replace the mesh and use less force next time.
• Pet-proof bonus. If you’ve got a cat or dog that pushes through screens, upgrade to “pet mesh” (heavy-duty PVC-coated polyester at around 0.9 mm thread). Fits the same spline and frame, but the dog can’t push through it.

The Mick rule

The frame almost never needs replacing. The mesh and spline are the consumable parts. Use charcoal polyester or aluminium mesh — fibreglass is false economy in Australian sun, and you’ll be doing the same job again in two years if you cheap out. If you want it to last on a north or west window, spend the extra $5 on aluminium and forget about it for a decade.

Got a fly screen frame that’s actually beyond saving — bent or corroded? Send us a write-up.