One for the Polycarbonateists

[8ob]

A question for the sage, I am insulating/double skinning the mancave ceiling and would like to use Polycarbonate sheets on the underside of the existing box profile clear sheets, available from Wickes are 10mm and 16mm twinwall or 25mm triple wall. Without blocking light with centre struts etc would any of these self support through the middle @ 900mm wide while only being fixed around edges without sagging like bingo wings the second the sun comes out?

Bob

 

[Barlidge]

Don't know if you remember the lean to I had at the back of the house in Biggleswade Bob? that was only 10 twinwall and it blocked a surprising amount of light. At least there the rain could keep it half clean but as an inner skin wont it collect dust over the years which will block out more light?

Edit: I remember when I was doing that one that the thicker ones could self support a surprising span.

 

[Screwdriver]

900mm is pushing it I think or maybe that's the maximum.

I found this article which has a lot of useful info: https://www.thepolycarbonatestore.c...ult/data_sheets/multiwall technical quide.pdf

I was looking for fire resistance

There are different requirements for internal and external use. I'd be wary of cladding the entire ceiling in something with unknown fire retardant properties. Wickes appear to be somewhat non-commital "it meets the regulations". I think polycarbonate does have some inherent protection, depends what you're doing in your shed I guess.

 

[8ob]

I was thinking of removable anyway Bruce, I would have thought dust and dead flies will get in there. I happened across a load of that steel studwork to hang the ceiling off and wanted to set the steels to suit the polycarbonate sheets, dont fancy getting up there again if it all sags

 

[mike os]

As it’s only insulation 25mm will easily span 900

 

[Barlidge]

Found this on Theplasticpeople

"As a guide, choose 16mm multi-wall at minimum if your support rafters are 980mm apart. Due to varying pitch factors, wind loading and snow loading we recommend that 1050mm is the maximum distance between rafters.
Choose your multiwall polycarbonate sheets.
Sheets come in different sizes up to 5m x 2m. It is best to use sheets no wider than 1050mm wide to allow for adequate expansion and contraction. "

 

[eLuSiVeMiTe]

The UK's Top Supplier Of Polycarbonate | The Polycarbonate Store

The Polycarbonate Store is the number one choice for Polycarbonate Sheet, Polycarbonate Sheets, Polycarbonate Roofing Sheets

www.thepolycarbonatestore.co.uk

Had good service from these guys.

Can't see 900 being an issue. It's surprising rigid.

 

[Parm]

It will sag. My neighbor did the same after much consultation of the internet. For the sake of another bit of timber do it properly.

 

[eLuSiVeMiTe]

It's going under the supports internally. It's not going to be out in the elements and twin wall poly is stronger than it looks.

 

[J1nx]

I’ve got this installed inside and it spans at least 900 (off top of my head it’s more like 1200), no noticeable sag and good insulator, significant reduction in light however and it’s only been up since October...
https://www.cabp.co.uk/Roofing-Shee...all/16mm-Polycarbonate-Sheet-9-Wall-Clear.htm

 

[8ob]

The light reduction worries me, think I will get a sheet tomorrow and try it to see how much light is lost.

Bob

 

[pedrobedro]

The light reduction worries me, think I will get a sheet tomorrow and try it to see how much light is lost.

Bob

We have some as a vent in the back end of the greenhouse and it blocks more light as it gets older.