# Vent Flashing for Low Slope Mineral Surface Roll Roofing



## Thumbhammer (May 19, 2011)

Just tore off a asphalt shingle roof over a very slightly pitched addition to the garage. I'm going to replace the shingles with some mineral surfaced roll roofing. The roof has a couple of plastic roof vents and a Metalbestos gas vent.
Should I just put down the felt and the roll roofing and then install the vent flanges on top of the roll roofing, perhaps with a ring of silicone caulk under where the vent flanges are nailed through the roofing, and spread asphalt over the edges of the flanges? Or should the vent flanges be nailed to the sheathing,with the felt and roll roofing put on over the flanges? 

I looked on the web for a detail, but didn't find any.

Thanks!


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## Talos4 (Aug 10, 2006)

Check out the attached detail 

It will give you the basics of the install.

Flange on top of the membrane.
Put another layer over the flange. 

Are you heat welding the membrane or nailing it? If your nailing it, nail the second membrane over the flange and use roof cement and cloth NOT silicone to seal around the flange.


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## Thumbhammer (May 19, 2011)

Thanks for the reply. I'm using Owens Corning 2" selvedge mineral surface roll roofing applied over two layers of 15# ASTM roofing felt. Are you referring to fiberglass cloth?
http://roofing.owenscorning.com/docs/datasheets/data_msr.pdf
http://roofing.owenscorning.com/docs/datasheets/data_fiberglasfelt.pdf


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## Talos4 (Aug 10, 2006)

No, I mean an asphalt cotton cloth usually available in widths 4-12" in width. 

An example

http://www.homedepot.com/buy/buildi...t-henry-185-asphalt-cotton-fabric-125925.html

Using a round tipped trowel, put a layer of roof cement over the seam around the flange overlapping the Mod bit membrane and the seam 2-3" about a 1/4" thick. apply the cloth over that spanning the seam. make sure the cloth is "lightly" pressed into the cement to make good contact with the cement. 

Then another layer of roof cement covering and ovelapping the cloth.

This is called "3 coursing" the seam.


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## Thumbhammer (May 19, 2011)

Yesterday I picked this up before I read your suggestion:
http://www.homedepot.com/Henry/h_d1...splay?langId=-1&storeId=10051&catalogId=10053

Do you think this would be OK?

Thanks


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