6 months protection over OSB boards

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I have built a large shed with a flat(ish) roof (1 in 35 fall). I have EPDM membrane for the roof, but watching lots of videos, I saw recommendations not to lay EPDM in cooler weather as the creases will never drop out, and as my membrane has been stored for a good 6 months I expect the creases will be especially bad. So, after I boarded the roof in 18mm OSB3 I laid a new blue tarp over the top and fastened it to the rough fascias with battens and screws, with the intention of laying the rubber roof on the first dry, sunny week of next spring.

That was 2 weeks ago, today I poked my head in and noticed that the blue tarp isn't weather tight as there has clearly been water coming through from above. Clearly I can't leave it like this for 6 months or my OSB3 will be soaked through.

My ideas are:
1) Remove tarp and replace with some form of proper roof membrane, overlapped as per the instructions and held down with battens running up and down the fall of the roof. But what membrane would keep the water out? Genuine question, is roof membrane actually waterproof or do the tiles do that part of the roof system?
2) Remove tarp and replace with a heavier-duty tarp. I realise blue plastic tarp is the cheapest, nastiest sort. But what grade/colour of tarp would be adequate?
3) Remove tarp, put some heavy gauge plastic sheeting down, lay tarp over (as wind protection for the waterproof plastic sheeting) and refit battens.

What would you do? I really don't want a creased up EPDM roof so I am keen to hold off on the laying until spring.

Edited to add: I'm after a temporary covering idea that I can remove in spring, before fitting the EPDM with the relevant adhesives. Re-reading my OP that wasn't very clear!
 
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The blue ones are not totally weather proof
Why not just lay your rubber over the roof and roll it back to glue down when your happy to
 
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I used a heavy duty tarp over one of my sheds for a temporary cover about 3 years ago.
Battened under the eaves on one side, pulled tight over the apex and battened under the eaves on the other side. End over hangs were folded and battened down. Still there now because it's not a 'working' shed, just somewhere to store things like paint, BBQ and kids garden toys. It's still waterproof though so not intending to replace it any time soon.

 
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I have built a large shed with a flat(ish) roof (1 in 35 fall). I have EPDM membrane for the roof, but watching lots of videos, I saw recommendations not to lay EPDM in cooler weather as the creases will never drop out, and as my membrane has been stored for a good 6 months I expect the creases will be especially bad. So, after I boarded the roof in 18mm OSB3 I laid a new blue tarp over the top and fastened it to the rough fascias with battens and screws, with the intention of laying the rubber roof on the first dry, sunny week of next spring.

That was 2 weeks ago, today I poked my head in and noticed that the blue tarp isn't weather tight as there has clearly been water coming through from above. Clearly I can't leave it like this for 6 months or my OSB3 will be soaked through.

My ideas are:
1) Remove tarp and replace with some form of proper roof membrane, overlapped as per the instructions and held down with battens running up and down the fall of the roof. But what membrane would keep the water out? Genuine question, is roof membrane actually waterproof or do the tiles do that part of the roof system?
2) Remove tarp and replace with a heavier-duty tarp. I realise blue plastic tarp is the cheapest, nastiest sort. But what grade/colour of tarp would be adequate?
3) Remove tarp, put some heavy gauge plastic sheeting down, lay tarp over (as wind protection for the waterproof plastic sheeting) and refit battens.

What would you do? I really don't want a creased up EPDM roof so I am keen to hold off on the laying until spring.

Edited to add: I'm after a temporary covering idea that I can remove in spring, before fitting the EPDM with the relevant adhesives. Re-reading my OP that wasn't very clear!
I did what Datarebal suggested: lay the EPDM down, allow it to overlap the sides and screw battens - ideally all around as you don’t want wind catching it and ripping it.

if you don’t want to use it, then buy a roll of DPM - I had a large garden office covered with it for 18 months and it kept dry.

If the shed roof gets full sun, you will find the EPDM will soften nicely after a couple of hours even in winter sun.

when you lay, I recommend

1. vacuum the roof and the EPDM to remove as much dust as possible.
2. I found the white glue doesnt hold that strong, so I glued OSB and EPDM
3 I strongly recommend getting a Karnedean roller - it’s fantastic for EPDM.

 
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Thanks all - I've now ordered a heavy duty tarp from an online tarpaulin specialist that is specifically waterproof and multi-ply. Buy cheap, buy twice as they say!

The EPDM was pretty expensive by comparison (I seem to recall it was about £500 for the rubber alone) and we've already had some pretty vicious winds in the last couple of weeks. I'll happily whizz screws through the battens holding the edges of a sacrificial tarpaulin into the vertical edges of the roof deck but with EPDM I'd be concerned about rendering the sheet unusable if something gets torn. So, better I just leave it until I can fit it "properly". (y)
 

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