Need a vent for 8" slates

[any_name_you_wish]

Hello there

I'm trying to fit an extractor fan into a room that's built in a dormer. The outside walls of the dormer are vertical 8" slates. I've hunted for a suitable vent but the ones I can find don't work with 8" slates. Even when they could be cut down to size they'll only work with 10-12' slates.

Can anyone point me in the right direction?

Thanks!

 

[foxhole]

https://www.roofingventilation.co.uk/MobileDetail.php?Prod_ID=4499

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