# Roof top venting



## Qball415 (Nov 20, 2010)

I have a job that has an opening skylight on a flat roof and vents need to be moved 10' min, vents thru roof are plastic. In order to move vents they will be tied and plumbed horizontally, does this have to be in cast iron?


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## 504Plumber (Jan 26, 2011)

Qball415 said:


> I have a job that has an opening skylight on a flat roof and vents need to be moved 10' min, vents thru roof are plastic. In order to move vents they will be tied and plumbed horizontally, does this have to be in cast iron?


I wouldn't see why it would have to be unless you have new fire codes?


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## Widdershins (Feb 5, 2011)

Qball415 said:


> I have a job that has an opening skylight on a flat roof and vents need to be moved 10' min, vents thru roof are plastic. In order to move vents they will be tied and plumbed horizontally, does this have to be in cast iron?


I'm assuming plastic was approved when it was built?

I see no reason to transition to a different material.


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## Plumb Bob (Mar 9, 2011)

Qball415 said:


> I have a job that has an opening skylight on a flat roof and vents need to be moved 10' min, vents thru roof are plastic. In order to move vents they will be tied and plumbed horizontally, does this have to be in cast iron?


Plastic should be protected from sun light, I use spray paint


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## Qball415 (Nov 20, 2010)

We repiped a couple bathrooms and used existing penetrations for vents. Inspector climbed to the roof noticed opening skylight and vents were too close. He mentioned to G.C that he wants them tied together and plumbed in cast on roof. 4 total.


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## rzp 06 (Mar 21, 2012)

They are too close.. But why go to cast?.. :blink:


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## Qball415 (Nov 20, 2010)

rzp 06 said:


> They are too close.. But why go to cast?.. :blink:


That's my question. Is why the inspector would require them plumbed in cast? I know we can paint plastic with high temp paint, I wonder if it has to do with contraction and expansion of the plastic, warping, bowing...


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## Plumb Bob (Mar 9, 2011)

Qball415 said:


> We repiped a couple bathrooms and used existing penetrations for vents. Inspector climbed to the roof noticed opening skylight and vents were too close. He mentioned to G.C that he wants them tied together and plumbed in cast on roof. 4 total.


I have had to transition to cast to stub through fire walls but never a roof.


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## Gettinit (May 9, 2012)

How high is the parapet? Any reason you couldn't just extend it (ordinance or parapet too high)? As long as you are only contending with one high wall it shouldn't have to extend above the wall.


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## revenge (Jun 30, 2011)

pvc gets brittle out in the eliments may crack or bow etc use unistrut and move them use fender washers for grade look at the bright side change order right


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## Plumb Bob (Mar 9, 2011)

Qball415 said:


> That's my question. Is why the inspector would require them plumbed in cast? I know we can paint plastic with high temp paint, I wonder if it has to do with contraction and expansion of the plastic, warping, bowing...


I would just do it and move on, the GC is going to have more work than you patching the roof.


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## MarkToo (Dec 17, 2011)

Can you not just extend the vents upward?

By code we only have to be 3'3" above an openable window.


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## MarkToo (Dec 17, 2011)

revenge said:


> pvc gets brittle out in the eliments may crack or bow etc use unistrut and move them use fender washers for grade look at the bright side change order right



You ran out again. You were supposed to let me know when you needed more.

Here you go...........................................................................................................................................................


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## deerslayer (Mar 29, 2012)

marktoo said:


> you ran out again. You were supposed to let me know when you needed more.
> 
> Here you go...........................................................................................................................................................


lmao


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## DesertOkie (Jul 15, 2011)

I hate skylights especially the opening ones.


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## Gettinit (May 9, 2012)

Do they have to open? Why can't they be "permanently" closed?


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## Qball415 (Nov 20, 2010)

3' above or 10' away is code here.

Skylights were installed to be available to open and shut.


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## DesertOkie (Jul 15, 2011)

Qball415 said:


> 3' above or 10' away is code here.
> 
> Skylights were installed to be available to open and shut.



I thought you were supposed to be 3'over parapit.


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## Widdershins (Feb 5, 2011)

Qball415 said:


> That's my question. Is why the inspector would require them plumbed in cast? I know we can paint plastic with high temp paint, I wonder if it has to do with contraction and expansion of the plastic, warping, bowing...


My gut tells me he's just being a hardass about the cast -- The penetrations definitely have to move away from the skylight. The cast iron requirement seems bogus, though.


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## 504Plumber (Jan 26, 2011)

I see no reason to do it in cast, seems just a tad silly to me. We work for an architect that Only wants one vent stubbed out the side of the house, he uses metal roofs, we stub PVC out with zero problems.


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