Fly screen escape window: clear the mesh first

You are in a bedroom on a warm night. The stairs are the normal way down, and this window is the way out if they are not. A fly screen escape window problem starts when the mesh becomes a bar across that clear opening. You can stick a sheet on for the insects. You still have to get it out of the way, quickly, and the sash has to stay open without you holding it.

This is not a ban on insect mesh, and it is not a certificate for one. England's Approved Document B volume 1, paragraph 2.10, describes the unobstructed opening. GOV.UK treats that document as fire-safety guidance. Products Compared compared amazon.co.uk listings for tesa Insect Stop with those public pages, without a laboratory test or a survey of your house. A qualifying purchase can earn us a commission at no extra cost to you.

In short

If this window is the way out, you must be able to clear the mesh quickly, with the sash staying open on its own. A stick-on sheet is not banned, and a tesa sheet is not approved for escape. The England figures below are not the rule in Scotland, Wales, or Northern Ireland.

What an escape window has to let you do

An escape window has to let you climb out. That is a narrower job than a window that opens. The CNC Building Control easy guide treats inner rooms and first-floor habitable rooms as the usual cases. Do not stretch that into every casement in the house. A kitchen window over a sink, a bathroom fanlight, and a ground-floor room that already has a door are not the same problem.

The sash has to open far enough, and it has to stay open without being held. Paragraph 2.10 of Approved Document B volume 1 is the public description of that opening for England. If you need one hand on the mesh and the other on the stay, you do not have a clear exit. None of the tesa listings in our tesa fly screen comparison is sold as an escape window.

On an outward-opening casement, the sash has to pass through the hole you have covered. A sealed sheet on the inside meets the sash on the way back to the lock. Flaps and outward sashes are covered on fly screens for outward-opening windows. Clearing the mesh does not create an opening that was never large enough, too high, or painted shut.

The measurements, without the whole document

The quotable figures, from Approved Document B volume 1 paragraph 2.10, are an unobstructed openable area of at least 0.33 square metres, and at least 450 mm high and 450 mm wide. The bottom of that openable area should be no more than 1,100 mm above the floor. The sash should remain open without being held. People search for these as an escape window size in the UK. They are England guidance for dwellings, not a substitute for the PDF.

The CNC easy guide uses the same opening and notes that some windows need escape hinges to reach it. A restrictor that stops the sash at a crack for child safety can also stop you reaching 450 mm. If the stay will not let the sash lie open on its own, fix that before you buy tape.

Unobstructed is the word that catches a fly screen. The openable area is the hole you can pass through after the window is open, not the glass size and not the packet size. Measure with the sash open and the mesh off or fully aside. If you cannot see at least 450 mm by 450 mm, and at least 0.33 square metres, the screen is in the way.

Do not paste these England figures onto a flat in Glasgow, Cardiff, or Belfast. Scotland, Wales, and Northern Ireland have their own building rules. You must still be able to clear the mesh quickly.

A mesh you can clear versus a mesh you cannot

A peel-off sheet and a screwed frame are different objects. Hook-and-loop can be pulled back if the tape lets go and if you have practised the pull. A frame screwed into the reveal, or a cassette that only retracts when a spring is willing, can be slower than the fire. If you cannot clear it in the dark, with the window staying open, it does not belong on that opening.

The top pick for a tall French window is the anthracite tesa Insect Stop Comfort sheet, 120 cm by 240 cm, at £9.51, with 4.4 out of 5 from 17,369 reviews on amazon.co.uk. The title is for French windows, and cut to size is not stated, so do not slice it for a small casement and call the offcut an escape hatch. Reviews split on outward-opening sashes: some peel a flap to reach the handle, and a fixed mesh can stop the window being used.

Open/Close Premium, 130 cm by 150 cm at £23.99, is sold to roll the mesh aside. It is still adhesive mesh, not a hinged escape screen. The white 130 cm by 150 cm Standard sheet at £7.20 suits a window you open only now and then, if a flap clears the lock. Neither price is a fire rating. If neither product lets the sash lock, stop buying adhesive mesh for that window.

A made-to-measure roller or a framed screen is a different class. It is better for escape only when you have proved you can retract it quickly. A jammed roll is worse than a sheet you can rip down. This comparison does not rank those frames. The buying guide is for sheet size, not a building-control sign-off.

This is not a survey of your house

Nobody from a mesh brand walks your landing and decides which window is the way out. Building control checks building work in its remit, not a fly-screen packet. Replacing the window, altering the opening, or fitting restrictors can be building work. Sticking tape on a frame that already opens asks only whether you have obstructed it.

The CNC guide treats inner rooms and first-floor habitable rooms as the usual cases. A ground-floor bedroom with its own door is a different layout, and a ground-floor inner room might still rely on a window. If you cannot point to the opening you would climb through, do not cover every window and hope one still works.

Products Compared cannot tell you that your particular sill is under 1,100 mm. Measure from the floor to the bottom of the openable area. If the sill is higher than the guidance, a fly screen is irrelevant until the window is.

Before you press the tape

Do this on the bare window first, in daylight, then again after the mesh is on. Open the sash fully and confirm it stays open without your hand on it. Look at the hole, not the frame. If restrictors or standard hinges stop you short of 450 mm by 450 mm, and short of 0.33 square metres, sort the window before any screen.

Fit only if the screen comes off that route in one movement you have tried. For hook-and-loop, that means a flap or a full peel that leaves the clear opening. Close and lock the window with the flap in place. If the lock will not throw, the mesh is in the way. The stick-and-trim order, when the sheet may be trimmed, is on how to fit a tesa fly screen. Do not follow that order on an escape sash until the clear-opening test has passed.

Try the clear in the dark, once, before a hot week makes you forget. You should not need a knife, a screwdriver, or a second person. If you do, take the screen off that window and use it on a window that is not the way out. A living-room casement you never climb through can still take a sheet. The bedroom that is your exit cannot take a lid.

We are not your building control body, and a £9.51 sheet is not approved for escape because it peels. If you cannot clear it quickly, do not fit it on that window.