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vendejp 09-13-2007 02:42 PM

Flat roof venting question
Hi all,
I have a newer rubber roof on a 1915 house. Its a square roof with the joists running the long way from from to back and the roof slopes from front to back (for water runoff).

Right now there are a few small turbine roof vents towards the front of the house.

I plan to raise the ceiling on the 3rd floor to the joists (leaving about 3 inches btwn insulation and roof for venting).

The problem is that these couple vents will now only vent 2 spaces between the joists (there will be no way for air to flow between joists) since I am raising the ceiling to the joists.

My question is this:
Is there some type of line vent for a flat roof? I was thinking a roofer could basically cut a slice the length of the roof (towards the front/higher section) perpendicular to the joists and cap it in some way?

There must be some solution for this.


(heres my wonderful 1 minute depiction)

the roofing god 09-13-2007 08:11 PM

you can make it yourself or use a clerestory vent to cap the vented area,depending on the roof pitch

Big Bob 09-13-2007 09:03 PM

clerestory Vent? Please help an old roof dog learn a new trick.
I taint near ever seen nothin like dat. Got a link or pic?

tryin to fix stupid here! Thanks for your help

the roofing god 09-13-2007 09:10 PM


the roofing god 09-13-2007 09:15 PM you go big fella!

vendejp 09-13-2007 09:31 PM

Thanks, I was having trouble googling "clerestory vent" for information as well. I now know what "net free area" is though. The image you provided is a "peak vent". Im having trouble visualizing how that piece would be applied to a flat roof.

Also, would this type of vent provide enough ventilation?


the roofing god 09-13-2007 09:47 PM

that`s what" air vent " calls it,the old "lomanco" term is clerestory vent,that`s what you call where the rafter ends at one side,rather than where a ridge beam connects to another,typical of contemporary style homes,the diagram he showed has pitch ,iyou would cut the 3/4" slot same as ridge vent, set elastomer sealant done on the roof where the vent will be secured,set the vent in it,w/a lower pitch I would flatten the gutter style lip before installation so there`s no problems

jayshultis 07-16-2008 11:26 AM

How id it go? I need to do something similar and would like to know the results.


vendejp 07-17-2008 03:45 PM

Project got reduced to a point that didnt include removing the ceiling. Sorry.


Originally Posted by jayshultis (Post 139822)
How id it go? I need to do something similar and would like to know the results.


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