Looking for advice on finishing this…

[junglejim]

I’m preparing to roof my timber frame build. The rafters are up to 15mm different in distance from the wall. I’m unsure how to proceed with sub fascia and/or fascia to  ensure everything is level and ready for the roof. I’m tempted to go for wood fascia/soffit rather than covering in pvc. 2 problems I have:

 

1. Rafter lengths up to 15mm different

2. osb overhanging rafter slightly so attaching directly to rafter would result in tilt.

A few other notes:

I haven’t clad the walls yet.

 

 I’m unsure whether I can get away with tiling the roof first but realise it will be easier if the fascia is on.

 

i could trim the osb so that I can fix directly to rafter ends.

 

 I’m unsure dimensions of wood needed.

 

 Any tips greatly appreciated as always.

 

 

[junglejim]

Ps. In this diagram the fascia is flush to the roof sheathing… this would seem to make sense as the breather membrane is below the counter battens so wouldn’t want to create a lip that could trap water.

 Am I right with that?

Edited August 11 by junglejim

[Mike]

1 hour ago, junglejim said:

1. Rafter lengths up to 15mm different

You need to string a line along across the top of them and trim them all to the same length.

 

1 hour ago, junglejim said:

In this diagram the fascia is flush to the roof sheathing… this would seem to make sense as the breather membrane is below the counter battens so wouldn’t want to create a lip that could trap water. Am I right with that?

You're right that it mustn't collect water, but it's normal to use a timber 'tilting fillet' to support the lower edge of the last row of tiles at the correct height; the membrane goes over the top of that. You may want to add a 'underlay support tray' as well, for belt-and-braces. Doing it this way means that the tiles do not rest on the fascia board, which can then be easily installed / repaired / replaced without disturbing the tiles.

 

If you're using an over-fascia ventilator, then follow the manufacturer's installation requirements / BBA certificate.

 

1 hour ago, junglejim said:

I’m unsure whether I can get away with tiling the roof first but realise it will be easier if the fascia is on.

As above, it will normally be easy to add the fascia board later, unless you're using a vent that doesn't permit that - in which case I'd personally choose a different vent.