Do I need an air gap behind fascia cladding?

[pedr0]

I'm building a shed: stud walls, breather membrane, roofing battens, featheredge.

So the roofing battens create an air gap behind the featheredge cladding.

I'm going to use some waney edge Douglas fir or larch on the fascia of the roof.

Can I nail the single fascia board directly onto the trimmer of the roof?
Or do I also need to create an air gap between the trimmer and the fascia?

 

[^woody^]

You could do as you proposed, but whether it performs as a fascia and makes rain drip away from the walls and not run down them is hard to say.

 

[pedr0]

I should clarify - the roof overhangs the walls by 200mm. So it's not the rain dripping down the front that I'm worried about.

It's that I understand you must have an air gap behind cladding to allow any moisture between the cladding and the wall to evaporate away.

So I've created an air gap on the walls,
But was wondering if I had to do the same on the fascia too. It's a bit of a faff that I was hoping to avoid. That said,
I'm putting a lot of effort into this and reckon the rest of the structure will last for many years. So I don't want the fascia to rot away.

Edit : I now see that my first post can easily cause confusion. Clarification: where I said roofing battens,
I meant the blue 25x50mm tiling battens. Ive used them on my walls to create an air gap behind the wall cladding. I have not used them on my roof.

Edit 2: my roof is a flat roof.

 

[^woody^]

Eaves/soffit boxing does not need ventilating. But if your wall vents into the eaves then you should ventilate the soffit/eaves