Solid polycarbonate sheet for canopy over door?

[Chris152]

I need to get on with finishing this canopy (started over a year ago), so I can get on with repairing the door frame, painting the door, plastering the hall and so on...

My idea is to get a solid polycarbonate sheet and screw it on - it doesn't need to connect to the brickwork/ render as it's just to keep the rain off the door area. I wanted to get 10 mm sheet but that's expensive, so thought 4 or 5 mm would do - the total dimensions of the area to be covered are 1200 x 2100 mm.
Would that work (ie, will there be enough support with the structure I have) and if so, how much oversize do the holes for the screws need to be to allow for expansion (this side of the house gets sunshine only in the evenings)? And is drilling into polycarbonate pretty easy (compared to acrylic, which apparently can split)?
I don't know if that's enough info to go on, but I'd appreciate any thoughts before I go spending a couple of hundred on the sheet and messing it up.
Chris

 

[MikeG.]

I've no comment on your material choice.

I will say, though, that you have to think through the implications of not using flashing. My view is that this will mean leaving a substantial gap between the sheet material and the walls. At least an inch. And given that most of the water that arrives at the door will have actually hit the wall and run down it, this isn't ideal. If you don't leave a gap you will have permanently damp bricks and render, with potential problems of moss growth, discolouration, and spalling to deal with in future......and that's just externally. Permanently damp walls have implications internally too.

 

[novocaine]

twin wall 6mm with mid sheet fastening (as you intend to do) recommended span is 500mm.
as mike has said, use flashing, a roll of self bonding is dirt cheap and more than worth doing.
drilling is easier than acrylic and it doesn't tend to split and fracture.

 

[Phil Pascoe]

I burned all the holes in mine.

 

[Chris152]

OK, I'm convinced - and I have some of that self-bonding flashing here for some reason so may as well use it.

The sheet I want to use is solid novocaine - the centres on the structure area little less than 50 cm so hopefully they'll support it fine.

Really appreciate all your replies.
C

 

[Just4Fun]

My mother had something similar fitted on her house last year. It was fine until a winter storm tore the framework away from the wall. It is a lot of area to catch the wind - and hers was smaller than yours. Based on her experience I suggest you put some spacers between the polycarbonate and the supporting framework so there is space for the wind to escape, working on the same principle as those "bullet holes" you sometimes see in banners stretched across a road.

 

[Chris152]

My mother had something similar fitted on her house last year. It was fine until a winter storm tore the framework away from the wall. It is a lot of area to catch the wind - and hers was smaller than yours. Based on her experience I suggest you put some spacers between the polycarbonate and the supporting framework so there is space for the wind to escape, working on the same principle as those "bullet holes" you sometimes see in banners stretched across a road.

Hmmm... the thought had occurred to me - it's facing west-ish so will get hit by the prevailing winds here - but I'd sort of put it from my mind. Maybe smaller, lighter sheets (twin-wall polycarbonate?) that would break away in the event of damage in a heavy storm and do less further damage than the whole canopy/ a single sheet of solid poly flying into the air? Or just grow wisteria up it and let the door get wet?!
Thanks.

 

[Robbo3]

I've used 10mm twinwall polycarbonate to cover a 5m passageway, a large carport using 3m x2m sheets, my workshop which is a concrete section garage, a couple of brick sheds & the front porch.
Brilliant stuff. Light to handle, easy to fix, will take a mans weight & is relatively cheap.
I think the passageway covering is now 15 years old & showing no signs of aging.
The carport is some 10 years old & has survived all the horrendous gales that we've had despite the large size sheets & minimal fixings.
I agree about the flashing. You'll regret not doing it.

 

[Chris152]

Thanks Robbo, I think that's the route I'll go down. It's not the look I wanted but hopefully it'll work ok, which is the main thing.
C