Cement board in place of fascia

[stb654]

Hi all,
I'm trying to ascertain if it's possible to use an external cement board in place of the usual upvc fascia board where the verge drips/drains over the side and into guttering. The idea is to have continuous (silicone) render rather than ugly plastic board over the top.

It's a warm roof and the firrings are counter to the joists; there is parapet to the non fall sides. The render board would sit flush with the blockwork below and cover the roof deck (OSB, Insulation). Where otherwise you would have the plastic fascia fixed to the ends of the roof deck.

Whether or not this would be ideal at such a junction I'm not sure. Any thoughts?
Can't seem to find examples of this done..

Thanks

 

[dontbelieveawordofit]

yes you can silicone render over cement board. with the correct prep.
contact the tech help of the product you intend using.
I’ve never seen it done and can’t visualise it . my personal opinion is I don’t think it’s a good idea or will look nice. your’e talking about visually ‘merging’ the roof and wall.
you can get ‘ugly plastic boards’ in different colours too just fyi.
and your cement or construction board must state external /water and frost proof

 

[^woody^]

It will move and flex with the roof, and not only crack the render at the joint with the walls, but may actually crack itself.

 

[dontbelieveawordofit]

yes the walls and roof expand and contract at different rates so would have to be rendered independently of each other using stop beads so shouldn’t really be an issue.
also appropriate tape or mesh would need to be used in your roof joints.