Vent pipe flashing

[supton]

Realized I never got around to a to-do that I've had on my list for, err, a couple of years now. Every so often the vent pipe will take an ice dam, and I'll get water in the house. Finally remembered I needed to do this, nothing like the here and now. So I bought some DAP roof stuff that says it can go on wet. But now I'm realizing: I don't know what I should seal.

The two shingles on either side of the flashing are "loose"--that is to say, I can pry them up, they are not sealed to the shingles underneath them, much less the flashing. Contractor did put a bead of seal around the shingle and flashing, in the back; but that is all cracked now.

Should I just pry up the shingles, put down caulk on top of the flashing, and let the shingles sit back down? Then put some on top of the shingle/flashing interface? Basically: just caulk the heck out of the area?

Do I need to nail down the front of the flashing? It seems to me that it should be open--any water that gets under the flashing should be allowed to flow out. So while it looks bad I think it ought to sit like that...

For the record: when it ice dams, I remove snow from around the vent pipe, and the leak stops. So it's not from someplace else.

 

[Delta]

Although you shouldn't have to seal "no caulk" flashing, I have seen some people seal the upper part under the shingles (on top of the flashing). I wouldn't nail the bottom of the flange. If it was me I would replace the whole thing. I normally used the all black plastic ones with no issues; they always seemed to lay flatter, for me anyways. For less than $10 it's piece of mind.

 

[supton]

I see your point; any issue with dealing with 40F shingles? I'd be concerned about prying and breaking--although I do have leftover shingles if one were to break.

I'm a bit surprised at how beat up the shingles are round there--apparently I was not as gentle as I thought with the roof rake!

 

[expat]

Originally Posted By: supton

Do I need to nail down the front of the flashing? It seems to me that it should be open--any water that gets under the flashing should be allowed to flow out. So while it looks bad I think it ought to sit like that...

For the record: when it ice dams, I remove snow from around the vent pipe, and the leak stops. So it's not from someplace else.



IMO the flashing should have been fastened down front and rear on top of a good bead of mastic applied all round.

Use scews or nails of the same metal as the flashing and apply mastic under the head before seating the fastener.

 

[Delta]

Honestly roofing is best left to a hot day. I'd be scared of breaking them. Not sure what this winter will hold out, if it's anything like us here in PA there's no snow predicted for a while. As far as the shingles taking a beating, looking at the pictures, I've never seen an Architectural roof laid out like that... I'm kind of partial to metal roofing myself. A little Lexel caulking and it's mostly fixed.

 

[supton]

The more I look at it.... the more I think I should squirt caulk under the metal, then screw it down. Seems wrong, but: this vent pipe is run 2' from the roof edge. So I "always" have a ridge of ice in that area. That's probably what lifted up the flashing in the first place, water backing up in this area.

Caulk and screw, and maybe the issue will go away...

 

[supton]

Originally Posted By: Delta
Honestly roofing is best left to a hot day. I'd be scared of breaking them. Not sure what this winter will hold out, if it's anything like us here in PA there's no snow predicted for a while. As far as the shingles taking a beating, looking at the pictures, I've never seen an Architectural roof laid out like that... I'm kind of partial to metal roofing myself. A little Lexel caulking and it's mostly fixed.


Wouldn't be the first year I left a ladder on the house so I could more easily scrape snow. Did that for a couple of years, as it would ice dam badly--then put the new roof on, and got a couple more years... now it only ice dams in this one spot.

But with the winter we've been having... I might not have any issues!

This vent pipe is barely a story up, so I could very easily just pull snow from it whenever I wanted to, and wait for next summer.

 

[supton]

After doing some more reading, it appears that nailing it down and sealing is the wrong thing to do. I suspect my best bet is to leave as-is for this winter, keep snow from the area, and replace the flashing next summer.

 

[Pop_Rivit]

Have you considered correcting the problem that is causing ice dams to form? The idea is to have the entire roof at the same temperature as the eaves. Since you're having ice dam issues, it's indicative of attic temperature control issues, and it has the potential to cause other issues, such as premature roof failure, heat loss and mold growth in the attic.

As a stop gap measure you could make a snow sock and set it so it points between the vent and the gutter. That will give the water a channel to follow to the gutter and prevent it from backing up to the vent pipe.

 

[supton]

This wall faces south, so heat rises and cause a natural ridge of ice at the top. As you can see, the vent is right next to the wall, so the flashing takes a beating as that ridge builds over winter.

5 or 6 years ago I had the roof stripped as I was tired of the ice dams on this side of the house. I read up on the ventilation issue, and had the contractor remove the planking under this shallow pitch. The prior owner did the roof but did not put ventilation under it--just jammed insulation in. Nice plenum put down, big vents in the eeves (like 4"x8", between each rafter), ridge vent. Grace snow and ice shield under almost everything, but apparently not around this vent.

No ice dams where they used to form--but I still get them on this pipe. I looked, and the pipe is sandwiched between plenums, so it should be well ventilated. However I think the insulation around the pipe is now pushed out of the way due to water--and I'd have to knock down a wall to get to the insulation. It's like literally inches away from my hand when I try to reach in.

The vent is in a really bad spot to reach to work, sandwiched between shower and a wall, and the wall looks to be planking behind sheetrock--so it's not a simple matter of poking a hole in.

 

[IndyIan]

You can get ice damming with perfect insulation when the attic tracks outdoor temperature above freezing in the day and then the outdoor temperature drops at night.

 

[supton]

No attic in this area, although I can easily see how heat will go right up the vent pipe.

We just changed from a brown exterior to green, so I'm hoping we'll get less of a ridge up there this year.

I strongly suspect the blown in insulation in this wall has settled nicely too, so there is probably plenty of heat in the area, even with good ventilation.

 

[JTK]

That's a tough spot supton. Real close to the edge where damming can occur and no easy way to insulate/ventilate the area. Caulking /sealing the lower edge is going to cause it hold water. Heat tracing that section might be an option for you to prevent pooling.

Get that soffit and fascia painted.. Kidding! One project at a time.

 

[supton]

Yeah, wanted to paint it this year, but one project at a time. That area is easy to do, it's the stuff on the other side of the house two stories up which is harder to do.

 

[sleddriver]

Originally Posted By: supton
After doing some more reading, it appears that nailing it down and sealing is the wrong thing to do. I suspect my best bet is to leave as-is for this winter, keep snow from the area, and replace the flashing next summer.


If it were me, I'd pull that one and replace it with 100% lead. Why? Because with ice dams here, that rubber/vinyl washer will be encased in ice, which will cause it to shrink, which will then lead to leaks, right down the pipe.

The uphill end of the flashing needs a good bead of roofing cement in an upside-down U shape to divert water to either side. The downhill side needs to be attached with a roofing nail at each corner, with a blob of cement between the flashing and the roof put down FIRST. Then another smaller blob under the head of the roofing nail before it's sunk home. Wipe off any that's squeezed out.

You don't want to seal off the bottom of the flashing between it & the roof with cement, just where the nail goes through. You want any water that gets up in there to be able to run out.

Also I like to see the shingles cut back in an arc, a bit more around the flashing/pipe. Keeps crud from getting stuck there.

 

[NHHEMI]

You have to nail the flashing down( top, sides, and bottom ). If you don't the ice works in under it and lifts it up allowing leaks. Just setting it on is not proper installation. Not in an area that sees snow and ice on the roof anyway. If just rain you can get away with only nailing the top and sides. The OP needs to nail the bottom down though.

If there is a rubber roof membrane under the shingles( we called it sticky-[censored] )that covers the area of the vent pipe you don't need any sealant on the nails/screws. If not and they go right into the plywood then many roofers use some type of sealant for the nails/screws( not over the heads - on the shafts )on flanges and flashing. We always use sticky-[censored] on the whole roof due to the New England winters so nail leakage is not a problem for our work.

If I was fixing what was shown in the photo I would replace the vent pipe boot/flashing with a new one( old one will be warped and leak no matter what you do now )and replace the shingles all around it making sure that I covered most of the way down the side with the shingles. leave the bottom of the flange exposed though - don't cover it.

 

[Pop_Rivit]

Originally Posted By: IndyIan
You can get ice damming with perfect insulation when the attic tracks outdoor temperature above freezing in the day and then the outdoor temperature drops at night.


Not on a properly designed roof/attic system. In 48 years of home ownership I've never had an ice dam, despite your statement.