Osb question for edpm

[chirpychippy]

Garden building, on the roof I have fitted 8x4 sheets of 18mm osb writing face down.

After much deliberation I'm going to lay epdm. At the moment the boards are screwed down and butted without expansion gaps.

If I cut expansion gaps will the edpm sink in the gaps? would I need to tape the gaps, in a similar way when applying fiberglass roofing, or not?

Thank you in advance.

 

[Alastairreid]

You don't need expansion gaps only if the boards were butting up to a wall.