Comments on: How to Fix a Leaky Gas Flue Roof Vent – Part 4

By: Bob Jackson

Bob Jackson — Sun, 28 Aug 2011 16:21:50 +0000

I don’t recommend it because caulking from inside the attic would be temporary at best and make repair/replacement more difficult when working on the roof. If your flashing cone looks like mine, the angle between the flue pipe and flashing cone is deep and narrow when viewed from attic, making it difficult to caulk and inspect the seal. If you decide to apply caulk, use a non-adhesive 100% RTV silicone high temperature caulk designed for this type of work. You might embed a heavy construction string (yellow or orange string found at home improvement stores) in the joint before caulking and let the free end hang down a couple of feet. When the roofer arrives for a permanent repair job, you can pull the string and sever the caulk joint like a zipper.

By: Brian

Brian — Sun, 28 Aug 2011 14:06:40 +0000

I have a similar problem. It looks like I could caulk my gap from inside the attic. Any problem with me first attempting to seal from inside before calling a roofer / hvac tech?

Thanks

By: DAW

DAW — Sat, 27 Aug 2011 05:42:35 +0000

Thanks for this marvelous post. I’ve got a similar problem that I have just decided to tackle. I bought the house after new shingles were put on and it has flue always leaked during a hard rain. I’m going to start with new caulk around the flashing. Your post has helped me identify another possible solution… a storm collar.

We’ll see how it goes and thanks for the very detailed info.

By: Bob Jackson

Bob Jackson — Wed, 14 Jul 2010 22:41:40 +0000

I’m aware of this rule and took notice of the vent stacks on homes in my neighborhood with 12/12 pitch roofs. Most stacks are no more than 2 to 4 feet high and badly fail the “2 feet higher than the highest point 10 feet away” rule. Here and there, a vent stack will be very tall that meets the “2 ten rule”, and it’s almost always crooked – probably from getting beaten up by the wind.

Think about it: a 10 foot tall vent stack is only 10 feet away from the roof surface on 12/12 pitch roof (45 degree slope). The rule becomes impractical very quickly, especially if the vent isn’t close the ridge.

The sample data gets more interesting on my drive to work. I’ve seen dozens of homes with steep roofs having short and tall stacks side-by-side at the same roof elevation. One stack cleared the ridge the other didn’t.

All I can say for certain is I’ve had no problems with my vents since and I can’t see them from the street anymore.

By: James

James — Wed, 14 Jul 2010 21:53:29 +0000

Bob,

Great job detailing your experience. Just one question, because I noticed that the stacks are now shorter. Since this is an exhust, are they not supposed to be two feet higher that the highest point of your roof ten feet away? This case your ridge line?

By: Bob Jackson

Bob Jackson — Thu, 20 May 2010 03:15:15 +0000

Can’t say for certain. It was Krylon flat black – I think enamel would be unnecessary.

By: Tom

Tom — Wed, 19 May 2010 03:29:36 +0000

Was it the Krylon Rust Tough Rust Preventative Enamel?

By: Bob Jackson

Bob Jackson — Sat, 15 May 2010 03:59:38 +0000

The HVAC tech used a Krylon exterior rust-proofing flat paint.

By: Tom

Tom — Fri, 14 May 2010 21:44:00 +0000

What kind of spray paint & Primer did the hvac tech use for your b-vent pipes?

By: Bob Jackson

Bob Jackson — Mon, 12 Apr 2010 09:19:15 +0000

The HVAC service tech only sealed the vertical seam on the cone flashing (because we kept the flashing) and the joint at storm collar. The vertical seam on the flue pipe shouldn’t need sealing. The rain cap slides over the flue pipe and doesn’t need sealing.