Mushroom vents on cold flat roof

[poolballboy]

Evening.

I am having to ventilate a cold roof and need some advise on sealing mushroom vents onto existing an felt roof. The current roof is a torched on felt roof and I need to add mushroom vents in between 6 or 7 joists. What i need to know is how to seal these mushroom vents to ensure there is no water ingress through the felt?

I will bore a 75mm hole and then sit the vent on top of the felt. is there a decent mastic to use between the vent and felt and then what is best to use to smear over the mushroom vent base to seal on top.

Thanks in advance

Andy

 

[datarebal]

get a felter to do it.. it isnt as easy as it sounds to get a reliable job

 

[poolballboy]

That will obviously be my default if it is not a DIY project.