11m osb okay for shed roof?

[steveo3002]

google seems to suggest it might be alright for a small shed , thought id ask on here as i always get steering the right way

including a bit of overhang i need 2850 x1600 on a flat /pent roof shed

doesnt need to meet any regulations and wont be jumping on it , but i dont want it sagging like a b&q shed after 6 weeks

also do i need to brace /add a bit inside to support the joins

thank you

 

[addjunkie]

The little shed in this picture is roughly 3m wide and has an 11mm osb roof, but has 3 off 4x2 supports running longitudinally. Onduline on top. Only issue has been me trying to lift it with a digger, when cleaning it out! Has had a foot of snow on top.

 

[sako243]

Osb and ply will sag eventually in a moist environment. Ideally you want to support them as @addjunkie says. I think the rule of thumb might be 600mm centres. I've not had issues with supporting them on those although if you're not in West Wales then you can probably get away with further.

 

[steveo3002]

yeah i was planning some kind of supports

 

[gaz1]

look your stood on it what maybe recomended means with support from other boards when stood on it with no extra support you can go through it moire so when your not aware its a thin roof board

id use 300-400 support with 11mm thats 12" or 16"

no one person tells you theyve used thin boards but they expect your up there sealing the thing

 

[magnet]

I've just done my 24 x 12 shed with 11mm osb its over a substantial roof structure of 6 x2 beams with stemming noggins in between. It fine but it's well supported.

 

[Seadog]

I used 9mm on my roof, with 3x2 spaced about 400mm (3.5m span). It takes my weight.

 

[Morrisman]

I used 18mm OSB with 24" centre beams, as it cost very little more than the thin stuff, and I knew I'd be climbing up there a few times laying roofing felt.

 

[Pete.]

I slung the 11mm osb that came with the shed and put 18mm ply on mine.

 

[steveo3002]

where the sheets meet , do i need to make an effort to join them somehow incase one moves after a while ?

 

[CaptainPugwash]

Screwfix still sell gallon tins of a bitumin type gloop for felting, i think they offer two variants.

Personally I have found OSB to actually be longer lasting than ply for this purpose; and it's slightly cheaper.

I think I would go for thicker than 11mm, on all but the smallest and budget conscious sheds.

Most of my local builder's yards sell two grades of felt, it may be worth checking you're getting good value on that as it isn't particularly cheap.

 

[steveo3002]

im getting rubber for it

 

[magnet]

This is my roof almost finished. I put the laths on after storm force winds had the felt off the old roof. This is 11mm osb.

 

[gaz1]

where the sheets meet , do i need to make an effort to join them somehow incase one moves after a while ?

on roofs or dormers the boards look more like brick work laid and nailed this keeps the beams from moving

on a smaller roof either do supports or add another rafter and screw them together this will fully support both boards with strong grip on either side

 

[Morrisman]

where the sheets meet , do i need to make an effort to join them somehow incase one moves after a while ?

I put a beam underneath wherever the ends or sides joined, as in my pic earlier.

 

[CornishPete]

18mm tongue and groove osb boards are the standard flat roof covering before any finish. Not much more than 11mm in the grand scheme.