Gap between patio door and floorboards

[wingit]

I've attached a photo of the gap at the end of the floorboards where they meet the patio door, there has been a bit of mould on the walls to each side. I'm thinking maybe just to marine ply the floorboards at that location, in preperation to lay oak boards on top, but wondering if the gap should be filled somehow? Thoughts and advice appreciated.

 

[Fred Blogs]

If it was me I would just clean out the gaps and fill them. Good luck with marine ply. Have a read about it. It isn't watgerproof nor is it rot proof only the glue they use is waterproof, if you are lucky. What they sell as marine ply these days is ruubbish and it is called BWP. All the BWP stuff that I have bought for my boat including Buffalo Board has delaminated within six months. I don't think the Buffalo Board lasted that long.

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[blup]

Shouldn't be a problem to use underlay if the sub floor is properly vented and dpc isnt breached.

Blup