Log store roof: Onduline/Coroline vs steel

[Crofter]

SWMBO has had enough of my shanty-town of log stores made from a motley collection of scrap (my favourite one is my Truckman pickup canopy mated to some pallets!). She does have a point since they are right outside the front of the house.

Rough plan is a 16ft long open fronted free-standing structure. I'll probably use sarking timber as it's fairly economical and is pressure-treated.

 

I'm swithering about the choice of roofing material. I was going to use corrugated steel, but maybe corrugated bitumen (e.g. Coroline or Onduline) would make more sense. It might be easier to get hold of, it's lightweight, and perhaps most importantly it's not going to take out anybody's eye if they walk in to it. The roof is going to work out reaching about eye level.

 

In favour of steel is that it seems a better product for about the same money, and I've used it before.

 

Thoughts?

[ProDave]

I used the bitumen stuff on my and it lasting well.

[Jeremy Harris]

My limited experience has been that onduline is easy to cut and fit, and seems to last a long time.  It's only real weakness is that it's relatively easy to damage, especially when installing it (it doesn't tolerate being stood on a corner well), but once installed it seems as robust as anything, really.  I'd opt for it, just because it's much easier to work with (although it does make a mess of saws and drill bits).

[Crofter]

Thanks... steel might be a bit OTT I suppose!

I'd searched the forum and found references to bitumen sheets sagging in hot weather etc, but that was in the context of a garage roof with much longer spans.

 

One mark against bitumen is that it comes in a standard sheet size of 2m... which almost certainly means throwing away a good chunk from each sheet (I probably need about 1.5m, so the off-cut is a bit small and fiddly)

[Russell griffiths]

I have the bitumen coated corrugated sheets from wickes and have found that they have sagged very badly when not fully supported, I have them on rafters at 600 centres and the dip in the middle is very bad. 

[DavidFrancis]

I've seen a lot of Onduline-type stuff sagging badly round our way. No idea if any of it was supported properly. I wouldn't be suprised if most of it wasn't.

[joe90]

I too have used onduline but it does sag if not supported a lot, my garage roof was fairly steep so less of a problem, best put it on ply (and don’t stand on it) but it does last well.

Edited May 9, 2020 by joe90

[Crofter]

I don't think it's going to sag... there will be a beam back and front, giving a span of around 1.4m. But maybe I should stick a third beam in. Or just use steel...

I think I'll get prices for both options and go from there.

 

[ProDave]

Mine are supported at 600mm centres and have not sagged.  Perhaps go 400mm centres if in doubt?

[Temp]

I used onduline on a chicken house. Works ok. How about lapped timber like this sort of thing..

 

 

 

[Crofter]

Yeah I see all the read-made stores use planked roofs... I'm not convinced it's a good idea, especially at the size I'm aiming for. I'd expect it to warp/shrink and start letting in water. They look nice on the smaller stores, though.

[Stones]

How about EPDM, single piece ordered cut to size online? That's what I used when building a log store at our last house. Yes you need a substrate for the EPDM but OSB is fine. Easy to do on your own and trims available to keep it neat. 

[DavidFrancis]

I made a planked roof for one of our stores about 5 and a half years ago. It leaked from the beginning, so I had to put a bit of DPM or something underneath. This is what it looks like now.  Bit different from Temp's picture! (The plywood's there because there's too much splashback at one end)