How does this flat roof structure look?

[Reejoc]

I'm happy with the construction of the actual deck but there's a couple of thing I would like to check:
1) The fascia board arrangement - specifically is there any advantage to bringing the board out with batons to create a cavity behind it. It would be simplest to just screw it to the end plates.
2) The windows are nearly full height but I need to create space for coving inside so there will be a gap above to fill. I obviously want to avoid cold bringing as much as possible so what do people think about the design below:

Many thanks for any comments

 

[Notch7]

I cant see where the firrings are going?

Personally I wouldnt choose to have an epdm edge trim sticking above a fascia cornice mould.

As far as I can tell you are doing an orangery style roof with a hidden box gutter. Or is 1 side discharging into a gutter?

If its a 3 sided extension, It lends itself to having fascia all round and discharging the water into a hopper.

 

[^woody^]

You need to design in a better drip on the roof edge/cornice to stop rain running down the face of the wall.

The epdm kerb is different to that as drawn, and you won't have (would not want) a section of fascia projecting past the roof deck.

 

[Reejoc]

I cant see where the firrings are going?

Personally I wouldnt choose to have an epdm edge trim sticking above a fascia cornice mould.

As far as I can tell you are doing an orangery style roof with a hidden box gutter. Or is 1 side discharging into a gutter?

If its a 3 sided extension, It lends itself to having fascia all round and discharging the water into a hopper.

Orangery style 3 sided extension - you're correct - and plan is for discharge into a hopper with no gutter. I'm not sure how else to create a proper kerb to keep the water without using the trim stuff hence the design above

You need to design in a better drip on the roof edge/cornice to stop rain running down the face of the wall.

The epdm kerb is different to that as drawn, and you won't have (would not want) a section of fascia projecting past the roof deck.

This is the stuff I was planning on getting. The need for something to project above the roof deck is to square the top of the roof, otherwise it will slope in line with the firrings. I could put a small timber upstand to give the fascia board more support? We're only taking 5cm above the deck at the maximum point.

The cornice design as it stands would project 150mm from the fascia

 

[Notch7]

It needs a different approach:

The easiest is to fit a sub fascia board, it closes off the rafter ends and extends up higher than the highest point of the flat roof, ie firrings at biggest position.

The top of this sub fascia board can have a capping board which is sloped back at 5 degrees. It needs to come over your cornice and extend back over the flat roof.

The capping can be dressed with epdm or code 4 lead.

I use 9mm tricoya mdf for the fascia board and 18mm osb for the sub fascia.

Cornicing I get from davuka.

 

[Reejoc]

It needs a different approach:

The easiest is to fit a sub fascia board, it closes off the rafter ends and extends up higher than the highest point of the flat roof, ie firrings at biggest position.

The top of this sub fascia board can have a capping board which is sloped back at 5 degrees. It needs to come over your cornice and extend back over the flat roof.

The capping can be dressed with epdm or code 4 lead.

I use 9mm tricoya mdf for the fascia board and 18mm osb for the sub fascia.

Cornicing I get from davuka.

Thanks for the info. Presumably this design with a capping board is for open cornice? If I used something like this is it acceptable to just stick this to the fascia, with the extra strength coming from the sub fascia board and the rain deflection coming from the projection and built in angle?