Over Facia Ventilation

[Mark 9002]

I'm planning to replace Facias and Soffits this summer with Rosewood UPVC. to match windows and doors.
My house is a detached timber framed house built early 90's and roof construction is rafters sheeted over with OSB, then felted and Tiled with concrete interlocking tiles. At present the soffit board is vented with continuous Grill. Rather than replace the soffit with another vented soffit, would it be possible to fit this kind of roofline with over facia ventilation, or does the OSB sheeting usually prevent the use of this type of ventilation method ?
Any input would be appreciated

 

[Alastairreid]

It can be done, but the bottom of the osb would need cut back and vent trays installed.

 

[Mark 9002]

Thanks for the reply Alstair,
I really wanted to go with the Over facia option mostly for aesthetic reasons. The house is 1 & 1/2 storey house ( 2 bedrooms and shower upstairs ) so loft space is really just a crawl space. At present the vented grill on the soffit has had sections over-boarded with ply ( Like this when we bought the place ) probably because of to much ventilation. On a windy day when I open the loft hatch there's a good Draft comes down through it even with the grill closed off in some sections. Cutting back the osb would be just to much of a work up for me as a DIY'er. Seeing as how its just a small loft space I think my best option would be to fit solid soffit and round vents every other Rafter (1200mm spacing). That would look better than whats there just now

 

[denso13]

I really wanted to go with the Over facia option

This is what I did as it was easier than fitting new ventilated soffit boards. I cut back the boards above the fascia, sarking in my case, and fitted eaves support trays.

The trouble with the round soffit vents is that they have to be quite close together to meet ventilation requirements. I think 200mm apart last time I checked.

 

[Alastairreid]

Also look at tile vents.