How Can I Stop Insects From Getting Through Gaps Around My Fly Screen?

Even a well-fitted fly screen can develop gaps over time. Frames warp, seals compress, and insects are patient. The good news is that most of the fixes here take under 20 minutes and don’t need a professional.

What You’ll Need

Tools

• Torch (for finding gaps in low light)
• Scissors or a craft knife
• Flat-head screwdriver
• Tape measure

Materials / Replacement Parts

• Foam or rubber weather seal strip (self-adhesive, 5-7mm wide works for most frames)
• Replacement spline (the rubber cord that holds mesh into the frame channel)
• Spline roller tool (if re-tensioning mesh)
• Replacement mesh (if the current mesh is torn or has holes near the edges)
• Draught excluder tape (for gaps between frame and reveal)

How to Fix It: Step-by-Step

Step 1: Find Every Gap Before You Fix Anything

Don’t guess. A lot of people re-seal one edge and miss the actual problem entirely.

• Wait until it’s dark outside, then hold a torch flat against the frame from inside the room
• Look for any light bleed between the screen and the window frame or reveal
• Run your hand slowly around the outside edge of the screen on a windy day and feel for airflow
• Note every gap, not just the obvious one

Step 2: Check the Seal Around the Frame

Most fly screens rely on a foam or rubber perimeter seal to close the gap between the screen frame and the window. Over time, this gets compressed, brittle, or falls off in sections.

• Remove the fly screen from the window and lay it flat
• Look for the seal channel running around the inside edge of the frame
• If the seal is flat, cracked or missing in places, peel it off completely and clean the channel with a dry cloth
• Cut a new self-adhesive foam or rubber seal to length and press it firmly into the channel, starting at a corner
• Refit the screen and check it sits flush against the window with no movement

Step 3: Re-Tension or Replace the Mesh

• If the mesh is sitting loose in the frame rather than pulled taut, insects will squeeze in at the edges where the mesh lifts away. This usually means the spline (the rubber cord that locks the mesh into the frame) has shrunk or perished.
• Look along the edge channel of the frame for the spline and press it with your fingernail; if it crumbles or moves easily, it needs replacing
• Use a flat-head screwdriver to lift the old spline out of the channel, working around the frame
• Pull the mesh taut and refit with a new spline using a spline roller, pressing it firmly into the channel as you go
• Trim any excess mesh with a craft knife once the spline is seated

Step 4: Seal the Gap Between Frame and Window Reveal

• Even a perfectly sealed fly screen can let insects in if there’s a gap between the outer frame and the window opening. This is especially common with retrofit screens or windows that have worn reveals.
• With the screen fitted, look for any visible gap between the frame edge and the window surround
• Cut draught excluder tape to length and press it into the gap on the window side (not the screen side, so it doesn’t interfere with removal)
• For wider gaps, self-adhesive foam strip in a larger width fills more space without compressing too quickly
• Recheck with the torch test before calling it done