I had a flat roof done and the roofers said it was ok for building regulations as although there were no vents (I guess they meant in the soffits), it is warm deck ventilation. Along the roof edges they did two different things on the sides as you can see in the photos. One side, where there was a gutter, had plastic horizontal soffits, whereas the other has the felt hanging over vertically (not sure what it's attached to), but no soffit underneath.
Now, where the felt hung over they left a gap of about 3 inches between the felt and the wall. I don't know what's up there but we then had mice getting into that room somehow, and as there were no gaps in flooring or skirting which was all new, we heard they can get up walls and work their way in. So we filled that gap all along with expanding foam. (there was also a very small gap of maybe 1cm at the top of the wall with the soffit which we also filled)
Afterwards, I thought maybe that wasn't a good idea as perhaps that gap was for ventilation & I've blocked it? Looking online it seems maybe I'm ok as ventilation there is only needed for cold deck and not warm which doesn't need air flow. But most pics don't have that gap. Appreciate any advice thanks.
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