Bi-fold doors have become one of the most popular home improvements in Surrey over the past decade. They open up the back of a house beautifully, blur the line between inside and out, and make a real statement. But there's a catch: they also create the widest, most accessible entry point for insects that any British summer can throw at you.
Standard fly screens — the kind you'd fit to a casement window — simply don't work here. Bi-fold doors fold and stack against one side of the opening, which means a fixed screen would either block the doors or be in the way entirely. You need a screen system specifically designed for wide, folding openings. The good news is that two excellent options exist. The challenge is knowing which one suits your situation.
The Challenge with Bi-Fold Doors
A typical bi-fold installation spans anywhere from 2.4 metres to 5 metres across — sometimes wider. The doors themselves fold concertina-style and stack neatly to one end of the frame. This means your fly screen needs to either fold with them, retract completely out of the way, or operate on a separate track that sits inside the bi-fold frame.
The two systems that solve this problem well are pleated fly screens and retractable cassette screens. Each has genuine advantages, and the right choice depends on your door configuration, how often you use the full opening, and your aesthetic preferences.
Option 1: Pleated Fly Screens
Pleated screens work similarly to a concertina blind. The mesh folds into fine pleats and the screen slides horizontally on a track, stacking neatly when not in use. For bi-fold doors, pleated systems are typically fitted within the door frame itself, operating independently of the door panels.
Pleated screens are well suited when:
- You want to be able to open just part of the screen independently of the doors
- Multiple people regularly use the opening and you need quick, casual access
- You prefer a screen that's visually present (you can always see it, even when stacked)
- Your bi-fold frame has sufficient depth to accommodate the top and bottom tracks
- You want a cost-effective solution for wider openings
The mesh on a quality pleated screen is very fine — often around 1.2mm aperture — which keeps out midges and smaller insects as well as flies. Look for aluminium frames rather than plastic; they're more rigid across wide spans and handle the British weather without warping.
Option 2: Retractable Cassette Screens
Retractable screens house the mesh in a slim cassette at one side of the opening. When you want insect protection, you pull the screen across and clip it to the opposite side. When you want full, unobstructed access, the screen rolls back into the cassette — completely invisible.
Retractable screens are well suited when:
- Aesthetics are a priority and you want the screen invisible when not in use
- You use the full opening regularly for entertaining or furniture movement
- Your property is listed or heritage — cassettes are small and unobtrusive
- You want a single handle operation rather than sliding panels
- The opening is up to about 3.5 metres wide (wider spans may need a mid-post)
Worth knowing: On openings wider than about 3.5 metres, a single retractable screen can lose tension and sag in the middle. A good installer will either recommend a two-cassette solution (meeting in the centre) or suggest that pleated screens are the better option for that span.
What to Measure Before Calling an Installer
Bi-fold fly screens are always made to measure — there are no off-the-shelf sizes for these openings. Before getting a quote, it helps to have the following ready:
- The clear opening width — measured from the inside of the frame on one side to the inside of the frame on the other, at the widest point
- The clear opening height — from the top of the frame to the finished floor level (or the threshold strip, if there is one)
- The frame depth — how much material there is inside the bi-fold frame for a screen track or cassette to attach to
- Which side the doors stack to — this determines where the cassette or stacked pleats will sit
If you're unsure of any of these, don't worry — a free survey will cover all of it. But having rough figures ready means an installer can give you an accurate indication of cost and likely lead time on the first call.
Questions to Ask Your Installer
Not all fly screen companies have equal experience with bi-fold openings. When you speak to an installer, it's worth asking:
- Have you fitted screens to this type of bi-fold frame before?
- Will the screen track fix into the bi-fold frame itself, or is it surface-mounted separately?
- What happens if a panel or the mesh needs replacing — is it a full system change or a simple part swap?
- Is the mesh UV-stabilised, and what's the expected lifespan before it needs replacing?
- Does the screen come with a warranty, and does that cover the mechanism as well as the mesh?
Colour, Material, and Which Side to Operate From
Bi-fold fly screens are available in a range of RAL colours and standard anodised finishes — white, grey, anthracite, brown, and black are the most common. A good installer will colour-match to your existing bi-fold frame so the screen sits discreetly within the overall look of the door.
Mesh options typically include standard grey fibreglass (the most common), anthracite for a more premium look, and ultra-fine meshes rated for pollen as well as insects — worth considering if anyone in the household suffers from hay fever.
The operation side matters too. If your bi-fold doors stack to the left, your screen cassette or stacked pleats will sit to the left, and you'll operate the screen by pulling it from right to left. If you have an obstructed area on one side (a wall return, a light switch, a planter), factor that in when deciding on the configuration.
The Bottom Line
Choosing a fly screen for bi-fold doors is a slightly more involved decision than for standard windows, but it's entirely straightforward once you understand the two main options. Pleated screens offer flexibility across wide openings; retractable screens offer elegance and invisibility when not in use. Both, when properly installed, will give you years of reliable insect protection without compromising the experience that made you choose bi-fold doors in the first place.
If you're based in Surrey and want to talk through the options for your specific doors, we offer free surveys with no obligation. We'll measure up, discuss both options, and give you a fixed quote on the day.