Polycarbonate panel thickness for secure windows?

I need to glaze 16 small panes (430 x 275 mm) in very strong, cast aluminium window frames (8 per frame, either side of the door). Is 3 mm frosted polycarbonate going to be impact resistant enough to keep people out? The building these windows are part of is in a fairly remote place, so security is a concern but for cost and aesthetic reasons we don't want to glaze with glass and install a metal security screen. The current ugly solution is boarding them up and securing with screws but this doesn't allow us light inside.

Cost is a consideration since I've been given permission by the company that owns the land to reglaze them and if I provide the labour they will supply the materials.

16 off 3 mm sheets, £3.85 each = £61.60
16 off 4 mm sheets, £5.14 each = £82.24
16 off 6 mm sheets, £7.70 each = £123.20

I've found lots of sites shouting "yeah polycarb is badass! It's unbreakable!" but not one that gives an idea for thinner sheets. Am I wasting money by going for thicker sheets? Or if someone's trying to get in might a 3 mm sheet be breakable?

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Vyger2 years ago

An elementary school here had a problem with kids breaking the low to the ground windows so they tried using polycarbonate panes to replace the glass. It stopped the problem with them being broken but then one of the more enterprising vandals got another idea. He tried to soften the pane with a lighter so he could melt a hole in it. Using only a regular cigaret lighter he lit the pane on fire instead of just melting a hole. The end result was 3 class rooms gutted and smoke damage throughout entire school building. The pane set the wooden window frame on fire which set the wall on fire. Oh, and then the fire department did major water damage while putting the fire out. It was pretty bad.

Jayefuu (author)  Vyger2 years ago

That's really useful to think about, thank you.

Are you sure they used polycarbonate not acrylic? I've read that polycarbonate is class 1 fire resistant so either the grade I'm looking at would be resistant to that or that used by the school wasn't? Definitely worth thinking about, thank you.

Vyger Jayefuu2 years ago

I was told they were polycarbonate but I could have been misinformed. I was called in to give an estimate on the cost of cleaning up the computers and other electronic gear. So I got a tour. It was an amazing mess from such a small source. But a lot of it was water damage. One of the fire hoses had a malfunction and made things a lot worse. But that was after the school staff had tried to put it out with dry chemical extinguishers. That went all through the air ducts and all the lights had to be taken down and cleaned.

RohitS881 year ago

i had installed polycarbonate panel by Gallina.in. Really its very secure for windows

Your main concer won't be breaking but flexing.

4mm is pretty strong and should survive normal sized rocks and stone but might have troubles with a house brick or similar.
You need to use very strong silicone to set them in the frame as otherwise they can pop out under enough pressure.
The black stuff for windscreens is really good or Sicaflex.
6mm would be a bit of overkill IMO unless you already encountered quite massive vandalism.
You can add a strong wire mesh on the inside fixed to the frame to give added support more violent attacks without the need to go 6mm.
When you do get the sheets ask if they are fore retardent as some can keep burning once set on fire, which would mean instead of a small ugly hole you have the shed on fire.

Jayefuu (author)  Downunder35m2 years ago

So you expect there to be too much flex in a 3 mm sheet for that size pane? I'll look up those two adhesives you recommended, thanks.

It depends on the type of frame you use.
For example the standard frames for acrylic sheets allow for about 1mm of free play to make it easier to get the panel into the frame and only have about 1cm of rim to hold the panel.
Without a strong sdhesive it is not too hard to push the panels out of the frame.
However, having a 3 or 4cm rim holing the panel with silicone and the frame would have to give up before the panel pops out.