Questions RE fitting a ventilated ridge to a slate roof

[Oxbow16]

Hi there

 

I’m hoping to install a ventilated ridge soon and after reading up there’s a few things I’m unsure about.  I wondered if anyone could help please?

 

The roof is Welsh slate and has stone/concrete ridge tiles (not sure which m but they are the old type).  There is ventilation already at the soffits.  In case it’s relevant, the roof has sarking boards, and the felt is the old style black stuff (1f?) laid directly onto the boards.  

 

1. Should slates be cut flush to or proud of the top battens?  Strangely, at the moment the slates are cut flush on one side, but on the other they overshoot the batten by around 75mm.  

 

2. What is a good size gap to have between the top battens at the ridge?  Currently they are 105mm apart.  Does that sound ok?

 

3. How much do ridge tiles need to overlap the slates by?  The current overlap is 97mm on one side (where the slates are cut flush) and 155mm on the other (where the slates overshoot).   

 

4. The existing felt fully crosses over at the ridge.  I’m presuming this would need to be cut to create an air gap, but am I right?  If so, how much to cut and remove? 

 

 5. And finally, any recommendations for a good ventilated ridge system?  I want something that is effective but also that won’t look too out of place on an old house with Welsh slate.  Obviously it will need to fit/overlap the slates sufficiently, given the above dimensions.  And also, because we live in a very rural area, it would need to keep vermin and insects out!  

 

Happy to upload photos and get any more details that might help with the answers.  

 

Thanks a million for reading.  I’ve been trying to answer these questions as best I can but not having much luck, so any help would be fantastic.
 

[Oxbow16]

If anyone has any thoughts I'd love to hear from you  

 

Many thanks