Cracked Roof Vent Boot Flashing Repair

I called several roofing companies in my area about the cracked vent boot, but none were available due to the once in 500 year flooding rains that fell on the Atlanta metro area in September. One company said they’d received 600 calls on Monday and most could only put me on a waiting list for a call back. I was quoted $125 to install lead pipe flashing for labor and materials, but no one could promise when they could get to it.

I was able to buy an Oatey Galvanized Base No-Calk® Roof Flashing at Lowes for about $7 that fit a 2″ inch vent pipe. I would have preferred a lead pipe flashing because it’s the best and longest lasting flashing solution that avoids the problem of cracked rubber boots. I can always hire a roofer when they’re not so busy and have lead flashing installed.

Oatey Galvanized Base No-Calk® Roof Flashing

Roof Vent Flashing Installation

Removing the old roof vent and installing a new one is simple:

1. Pry up the roofing nails used to attach the old flashing.
2. Gently lift up the shingles above the flashing.
3. Lift the flashing off the vent pipe.
4. Slide the new flashing over the vent pipe.
5. Tuck the uphill part of the flashing under the shingles.
6. Fasten the new flashing with galvanized roofing nails.
7. Apply a dab of roofing sealant to the nail heads and bottom tabs of the shingles that were disturbed.

The entire job takes less than 15 minutes. It seems easy and it is, unless you have a high and steep roof like mine. A 40 foot ladder is necessary to reach the roof from the ground and I’m not comfortable working so close to the edge of the roof. Time to hire a professional roofer, but none were available on short notice. What to do?

I got lucky and noticed a roofing crew working in the neighborhood. I asked the foreman if I he could install the new vent flashing. He said they were almost finished with the current job and could send someone over in 45 minutes. He asked if I had the new vent flashing, I said yes and showed him the Oatey No-Caulk flashing. He said he would install my flashing and add a rubber rain collar for extra protection for $50.

Two men from the roofing crew a short while later as promised. They setup a 16 foot ladder by the garage and bear crawled up the hip ridges with a big block of foam rubber (i.e. an old couch cushion) wearing regular tennis shoes with amazing agility! Compare this to my Poor’s Man’s roofing shoes in this article. In this photo the roofer is getting into position to start work.

Roofer Bear Crawling along the Roof Hip

Here the roofer has pried up the nails and is removing the old vent pipe flashing.  The block of foam rubber grips the roof so he doesn’t slide off. The new flashing is tucked under the edge of shingle above him so it’s doesn’t slide away.

Removing the old Roof Vent Pipe Flashing

The new flashing is slide over the pipe, tucked under the shingles on the high side, and nailed to the roof.

BASF SONOLASTIC® NP 1 roof sealant is applied to the nail heads and bottom tabs of the roof shingles that were raised to install the flashing. This makes everything waterproof and ensures the shingles are glued to the next row so they won’t be lifted by the a strong wind.

Roof Sealant is Applied to the Nail Heads

Rain Collar – Fix a Leak in the Rain

Rain & Repair Pipe Collars are simply the rubber boot without the metal flashing. It acts like an umbrella to shed water over a cracked boot. A rain collar costs $5 to $10 and can be installed while it’s raining or wet for an emergency fix. No caulking, it stretches over the pipe for a water tight seal.

This is the new roof vent flashing with an added rain collar for extra protection.

New Plumbing Roof Vent Flashing with Rain Collar

Cracked Vent Boot – Post Mortem

The boot on the old Oatey all-plastic vent flashing was severely cracked/split in the places. This broke the watertight seal around the 2″ PVC vent pipe and allowed rain water to leak in and run down the vent pipe onto the drywall ceiling. This vent boot failed after about 10 years on the southern exposure of the roof.

Oatey - Cracked/Split Boot on Vent Pipe Flashing

A side view of the old vent flashing:

Oatey - Cracked Plumbing Vent Boot Flashing

I’ll have all my vent boots replaced with lead flashing when the roofing companies are less busy in a few months. Lead flashing lasts practically forever and almost never leaks because the rim of the lead flashing is folded into the top of the plastic vent pipe for a 100% seamless and waterproof installation. The rubber vent flashing costs $7 compared $30 for a lead flashing. The reliability of lead flashing is well worth it in my opinion.

Take care,

Bob Jackson

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I became aware of a possible leaky roof when I noticed water stain on the drywall ceiling. The water stain occurred during a period of record rainfalls and extensive flooding in the metro Atlanta, Georgia region. My area received about 17 inches of rain in an 8-day period! 17 inches of rain is a lot for an area that would normally less than 4 inches on average in September. With that much rain any roof leak, no matter how small, is likely to be noticed.

Water Stain on Drywall Ceiling due to Roof Leak

Finding the Leak

The main attic is above the room with the water stain on the drywall ceiling. To locate the source of the leak, I got a flashlight and went into the attic. The stain is the corner next to the exterior wall, so I focused my search in that direction. The PVC vent pipe for the basement bathroom plumbing rises through the roof directly above the stain on the ceiling. The vent pipe became an immediate suspect.

Take care to walk only on the wood joists when working in the attic. The ceiling drywall will not support your weight and you can fall through! Move slowly and carefully.

PVC Plumbing Vent Pipe

This is the lower end of the vent pipe – it’s covered by blown fiberglass insulation. The dark bits on the insulation are nut shells left by flying squirrels that sometimes get into the attic during the winter. I catch them in a box trap to take them to the park and set them free unharmed. Last winter, when I opened the box trap to set the squirrel free, he ran out and turned around, sat up and stared at me for while before scampering off into the trees. Whether confused or saying “thanks!”, I’m not sure. But I digress.

Lower End of the Plumbing Vent Pipe

I moved the insulation away to reveal the bottom of the vent pipe and ceiling drywall. The insulation and paper surface of the drywall were damp. I’m getting close to finding the leak.

Insulation Pushed Aside to Reveal the Drywall Ceiling

A closer look at the vent pipe penetration through the roof revealed daylight shining through around the vent boot flashing. This is the source of the water leak! Rain water is coming in around the vent boot, running down the side of the vent pipe and dripping onto the drywall ceiling. Persistent heavy rains caused enough water to leak inside to be noticed.

On the positive side, the Oriented Strand Board (OSB) roof deck is dry and untouched by the leak. If the roof decking were rotted, the shingles would have to torn up and the rotted section of deck replaced – a major repair effort!

Roof Vent Pipe Flashing - Daylight Coming In!

More rain was in the forecast and it might a take a couple of days to get a roofer over to repair the vent flashing. To minimize further water damage, I tied a towel around the pipe just above the horizontal brace. This is only a band aide solution.

Towel Tied Around the Vent Pipe to Catch the Roof Leak

Cracked Vent Boot

Now that I know what to look for, a crack or split in the vent boot is clearly visible in this photo (red square). The vent boot must hug the pipe tightly to form a watertight seal. The roof is about 10 years old and the vent boot has cracked from a combination of the UV rays from the sun, weathering, expansion and contraction from the heat and cold.

Cracked and Leaking Plumbing Vent Boot

The 2″ PVC vent pipe with the cracked boot is shown here in perspective to the house. The roof is a steep 10/12 pitch and the house sits on a hillside. A 40 foot ladder is needed to reach vent pipe from the ground. Time to call a professional roofer to make this repair.

Vent Pipe Flashing with Cracked Boot

This repair is continued in Part 2.

Hope this helps,

Bob Jackson

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