Extractor fan in roof?

[Deansplit]

What's the best way to fit a vent in a roof for en suite extractor fans? I can't really get the outlet to the exterior wall, it's a Victorian house and the ensuites have been added in the centre of the rooms. Would a normal 4" boiler style capped vent/pipe with the ali flashing, made for roofs do? Although I really need a way of preventing blow back.

I should mention that the roof has no overhanging soffit - the slates only protrude a couple of inches from the wall.


Any suggestions appreciated.

Thx

 

[stem]

Fit one of these in place of a tile. You will also need to fit a condensate trap at the bottom of the vertical section to stop condensation running back into the fan. Blowback is not normally a problem with a vertical stack as the wind blows across the top of the duct, rather than down it. A cowl will stop rain entering