Hail Damaged Roof Replacement: Part 4 – Gas Flue Vents

This project is continued from Hail Damaged Roof Replacement: Part 3 – Attic Ridge and Box Vents.

The Type B gas roof vents for the natural gas furnace and hot water heater are replaced with the installation of the new roof. New vent caps, storm collars and flashings are installed.

Roof Gas Flue Vent Replacement

Roof leaks most often occur at penetrations in the roof, such plumbing vents (happened to me), flue vents (also had that happen), chimneys (yep, bad luck again), attic vents and skylights. That’s three (3) roof leaks in the past 6 years that I’ve owned the home! Extra care and attention is necessary for watertight seal at roof penetrations such that these are on par with the “lifetime” warranty on the shingles. If a roofing contractor doesn’t want to rework and seal the roof penetrations properly, find another roofer or be prepared for leaks!

One of the three roofing contractor proposals I received did not include replacing the gas flue vent cap, storm collar and base flashing, while the other two roofers included this work in their proposals in the spirit of preventing callbacks for warranty work. The flue vents were not a line item in the insurance adjuster’s estimate, so this item needs to be negotiated or paid for separately. That one contractor who wanted to do the job quickly by reusing the old vent flashing and caulking the nail holes? I scratched that contractor off my list. Good thing too, because that contractor was recently doing warranty work on another home on my street to replace step flashing.

Below are the old gas flue vents after the shingles have been torn off. The base flashing is bent and has nail holes. I also wonder about that thick bead of caulk around the bottom of the flashing cone. Was that to fix an old leak?

Hail Damage Roof Replacement: Old Type B Gas Flue Vents

The stripped flue vent pipes are clearly seen in this photo (the OSB roof deck is being replaced to eliminate the attic box vents):

Hail Damage Roof Replacement: Flue Vent Pipes Stripped Bare

These are the old vent pipe flashing, vent caps and storm collars. The roof vent pipe flashing cones are original with the house. Not sure why there’s a thick line of caulk around the base of the cone; maybe to plug a former leak? Would you want these on your new roof?

Old Gas Roof Vent Base Flashing, Vent Cap and Storm Collars

These are the new DuraVent Type B gas vent parts: DuraCap vent cap, storm collar and steep roof flashing. The new parts cost about $75 per vent pipe – a very small fraction of the roof replacement cost. Why wouldn’t you have new flue vent flashings installed?

New DuraVent Steep Roof Flashing, Storm Collars and Vent Caps

Hail Damaged Roof Replacement: Part 4 – Gas Flue Vents

New Type B Gas Flue Roof Vent Installation

The GAF Shingle-Mate® roofing felt (equivalent to 30 lb felt) is installed on the roof deck first. Then an oversize sheet of GAF StormGuard® leak barrier (ice and water shield) is cut and applied over the vent pipe on top of the roofing felt. The Duravent steep roof vent pipe flashing is spray painted black, slipped over the vent pipe and nailed to the roof. Shingles are installed over the vent pipe flashing as the courses are laid. The storm collar will be installed, sealed with caulk and the vent cap installed.

Hail Damaged Roof Replacement: Roof Gas Flue Vent Flashing

The new Duravent vent pipe flashing, storm collar and vent caps. The vent pipes will be spray painted black with roofing paint.

Hail Damaged Roof Replacement: Type B Gas Flue Roof Vents

Notice the slot in the roof decking along the ridge for the ridge vents in the above photo.

Here’s a closeup of the new roof gas flue vents. The exposed nail heads at the bottom of the flashing are sealed with BASF SONOLASTIC NP1 caulk. Also notice the new ridge vent in the background:

Hail Damaged Roof Replacement: New Type B Gas Flue Vents

Another view of the finished gas flue vents, ridge vent and chimney cricket on the finished roof:

Hail Damaged Roof Replacement: Type B Gas Flue Vents and Chimney

Notice anything odd in the above photo? The house in the background is also having the roof replaced due to hail damage. The odd thing is the roof felt was run down the roof (from top to bottom) in violation of the manufacturers installation instructions (page 42). There is also an exposed area on the hip that never covered with roofing felt. This is what happens when a roofing contractor is in a hurry to do a job and takes short cuts where he thinks you can’t see the sloppy work. Fortunately, I hired a different roofing contractor who took the time to do the job right.

This project is continued in Hail Damaged Roof Replacement: Part 5 – Plumbing Vents.

Take care,

Bob Jackson

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2 Responses to Hail Damaged Roof Replacement: Part 4 – Gas Flue Vents

  1. Dan October 26, 2016 at 11:46 pm #

    Hi Bob

    Regarding the installation of the duravent flue vent. Did the roofer install the cap, flashing and storm collar or did you have an hvac guy come out and do it. I’m getting our roof replaced and was considering getting the gas flue vent replaced at the same time. Flue vent is probably original so about 40 yrs old.

    Roofer said they typically don’t do it but can.
    Getting a hvac guy out at the same time as roof replacement may be a logistic issue. Plus it’ll easily be couple hundred dollars just for them to do the job.

    Also, to replace the cap, flashing and storm collar, do you have to turn off the water heater. That’s the only thing using the vent. Thanks

    • Bob Jackson October 27, 2016 at 8:43 am #

      The roofers did all the work, including the plumbing vents. It’s best to have the vent boots/flashing installed with the new roof to minimize disturbing the shingles. If the roofers aren’t comfortable working the flue vents, ask if they’ll subcontract that to an HVAC contractor to simplify logistics/coordination.

      RE: Water heater
      I did not turn off the natural gas water heater but would have if the roofers had asked. My water heater is in the basement so it’s 3-1/2 stories (including the attic) to the roof. The flue gas would be fairly cool by that point.

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