Shingling Around Roof Vents

Chunkstyle

hi guys

can any of you tell me anything about the proper way to shingle around a spot roof vent, like a mushroom vent?

my understanding of what i'd call roofing's most basic rule is that everything on a roof needs to lap over whatever's below, in order to shed water. perhaps this is a pretty lame, novice oversimplification, but it's how i've been looking at things so far.

if this is correct, then wouldn't the bottom edge of the mounting flange on a roof vent need to be exposed, lapping over the shingles near the bottom of the vent? one roofing manual i checked shows it that way (surprisingly, many of the other books didn't even specifically address how to do it at all!). however, on the roof of my outbuilding, and the roof of my parents' house, i noticed that the shingles at the bottom edge of the vent are filled in over the lower part of the flange, cut around the profile of the vent. is this right?

i can see where, on a mushroom-type vent where there's a cap that overhangs the center part of the vent a bit, that overhang would prevent some rainwater from getting under the shingles over the bottom flange, but couldn't water running down the roof from above the vent still get under those shingles at that spot?

thanks!

Glasshousebltr

Under flash at the bottom, over flash from half way and across the top, stay away from nailing to close to vent.

Bob

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Bob

Grumpy

Jeez I can't put it into words. www.nrca.net do a search for their manual and I am sure you will find a detail.

minnesotaroofin

2 under 2 over

Chunkstyle

thanks for the replies so far, guys.

minnesotaroofin -- please forgive me for being dense, but what do you mean by 2 under & 2 over?

2 rows of shingles under the bottom end of the vent flange & 2 rows over the flange at the top?

and grumpy -- i'm writing this from my local library, and their computers won't let me view that manual. i could get to the site, but it wouldn't load -- probably something with the library's firewall not recognizing the manual applet. my internet connection at home's so slow that i doubt it'll work either. thanks anyway, though!

thanks!

minnesotaroofin

shingle up to the hole. first shingle that you have to cut. second shingle you cut. then install vent. next 2 or possibly three overlap vent.

AaronB.

I like to shingle OVER the holes (not nailing within the flange areas) and cut the half circle and slide it in. NO nails through the vent flange at or above the bottom of the vent hole opening. You are correct, IMO, about the bottom of the vent flange overlapping onto the shingles below with an exposed section the bottom.

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minnesotaroofin

Yes, I do it the same way Aaron. Easier to understand the other way.I teach all the new guys the way i explained first. for proper placement and coordination with the hook blade. Our vents are exactly 1 foot square + the 3 inch flange. so it makes for easy alignment since 3 tabs are 1 foot wide.

red_cedar

I do this as well, in order to cut the round curve I put my hand over the hole area and spread out my fingers then cut about an inch around that.
This way you are not fighting the shingle with the vent top.

AaronB.

Watch those fingertips. :Thumbs:

I teach my guys this way first so as not to create any confusion in MY WAY.

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Seamless Industrial and Commercial Roofing Systems, Residential Repair. For Those That Demand Quality!
Free roof inspections within 12 miles of our locale.

Glasshousebltr

Is there an echo in here?

Bob

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minnesotaroofin

I tend to let my guys figure it out for themselves which works better. sometimes in the winter it is best to shingle 2 up-- vent--- then over. real pain to get top nails in, with architecturals anyhow.

dougger222

I also do the two/two method.

With using the flat sided aluminum or steel Lomanco air vents it's easy to lift the shingles for nailing even in the winter with laminate shingles.

Minnesotaroofin, were do you work and what's the name of your business?

I'm also from Minnesota. Recently moved from New Richland (1.5hrs. S of TC) to Maplewood. Do new roofs and tear offs in between!

minnesotaroofin

http://Minnesotaroofing.com is our website if that is alright to post here. Who do you work for or your company?

AaronB.

I do not like the half and half methodology because if you have exposed flange above the bottom ofthe actual vent hole, water can blow in with driving rain conditions.

__________________
http://www.roseroofing.net/
Seamless Industrial and Commercial Roofing Systems, Residential Repair. For Those That Demand Quality!
Free roof inspections within 12 miles of our locale.

J2Jonner

The bottom of the vent flange is on top of the coarse below, but for aesthetics the next coarse was cut around the vent bottom. Should still be fine, but I'm rarely a roofer! :-) As you can see it's preference I think.

Cheers,
Jon